Gap 2 GUI Settings: runtime chirp timing, stream control gating, status readback (18/18 FPGA, 20/20 MCU)

Register map: 0x10-0x15 chirp timing overrides, 0xFF status readback,
0x03 CFAR threshold now wired to actual compare, 0x04 stream control
gates USB write FSM. Status readback sends 7-word packet (0xBB header,
5 status words, 0x55 footer) via toggle CDC.

radar_mode_controller: 6 cfg_* input ports replace hardcoded parameters.
usb_data_interface: stream_control CDC, status_request toggle CDC,
  SEND_STATUS state (3'd7), stream gating in IDLE/HEADER/RANGE/DOPPLER.
radar_system_top: 6 host registers + command decode for 0x10-0x15/0xFF.
radar_receiver_final: 6 host_* timing passthrough ports.

Testbench coverage: RMC 81 checks (+TG16 runtime reconfig), USB 77
checks (+TG15 stream gating, TG16 status readback, TG17 chirp opcodes).
Fixed iverilog 13.0 forward-ref for status_req_toggle_100m.

9_Firmware/9_2_FPGA/formal/fv_radar_mode_controller.v

@@ -66,6 +66,14 @@ module fv_radar_mode_controller (
     (* anyseq *) wire       stm32_new_azimuth;
     (* anyseq *) wire       trigger;
 
+    // Gap 2: Formal cfg_* inputs — solver-driven for exhaustive coverage
+    (* anyseq *) wire [15:0] cfg_long_chirp_cycles;
+    (* anyseq *) wire [15:0] cfg_long_listen_cycles;
+    (* anyseq *) wire [15:0] cfg_guard_cycles;
+    (* anyseq *) wire [15:0] cfg_short_chirp_cycles;
+    (* anyseq *) wire [15:0] cfg_short_listen_cycles;
+    (* anyseq *) wire [5:0]  cfg_chirps_per_elev;
+
     // ================================================================
     // DUT outputs
     // ================================================================
@@ -101,6 +109,13 @@ module fv_radar_mode_controller (
         .stm32_new_elevation(stm32_new_elevation),
         .stm32_new_azimuth  (stm32_new_azimuth),
         .trigger            (trigger),
+        // Gap 2: Runtime-configurable timing inputs
+        .cfg_long_chirp_cycles  (cfg_long_chirp_cycles),
+        .cfg_long_listen_cycles (cfg_long_listen_cycles),
+        .cfg_guard_cycles       (cfg_guard_cycles),
+        .cfg_short_chirp_cycles (cfg_short_chirp_cycles),
+        .cfg_short_listen_cycles(cfg_short_listen_cycles),
+        .cfg_chirps_per_elev    (cfg_chirps_per_elev),
         .use_long_chirp     (use_long_chirp),
         .mc_new_chirp       (mc_new_chirp),
         .mc_new_elevation   (mc_new_elevation),

9_Firmware/9_2_FPGA/radar_mode_controller.v

@@ -61,6 +61,17 @@ module radar_mode_controller #(
     // Single-chirp trigger (active in mode 10)
     input wire trigger,
 
+    // Gap 2: Runtime-configurable timing inputs from host USB commands.
+    // When connected, these override the compile-time parameters.
+    // When left at default (tied to parameter values at instantiation),
+    // behavior is identical to pre-Gap-2.
+    input wire [15:0] cfg_long_chirp_cycles,
+    input wire [15:0] cfg_long_listen_cycles,
+    input wire [15:0] cfg_guard_cycles,
+    input wire [15:0] cfg_short_chirp_cycles,
+    input wire [15:0] cfg_short_listen_cycles,
+    input wire [5:0]  cfg_chirps_per_elev,
+
     // Outputs to receiver processing chain
     output reg use_long_chirp,
     output reg mc_new_chirp,
@@ -173,8 +184,8 @@ always @(posedge clk or negedge reset_n) begin
                 mc_new_chirp <= ~mc_new_chirp;  // Toggle output
                 use_long_chirp <= 1'b1;         // Default to long chirp
 
-                // Track chirp count
+                // Track chirp count (Gap 2: use runtime cfg_chirps_per_elev)
-                if (chirp_count < CHIRPS_PER_ELEVATION - 1)
+                if (chirp_count < cfg_chirps_per_elev - 1)
                     chirp_count <= chirp_count + 1;
                 else
                     chirp_count <= 6'd0;
@@ -226,7 +237,7 @@ always @(posedge clk or negedge reset_n) begin
 
             S_LONG_CHIRP: begin
                 use_long_chirp <= 1'b1;
-                if (timer < LONG_CHIRP_CYCLES - 1)
+                if (timer < cfg_long_chirp_cycles - 1)
                     timer <= timer + 1;
                 else begin
                     timer <= 18'd0;
@@ -235,7 +246,7 @@ always @(posedge clk or negedge reset_n) begin
             end
 
             S_LONG_LISTEN: begin
-                if (timer < LONG_LISTEN_CYCLES - 1)
+                if (timer < cfg_long_listen_cycles - 1)
                     timer <= timer + 1;
                 else begin
                     timer <= 18'd0;
@@ -244,7 +255,7 @@ always @(posedge clk or negedge reset_n) begin
             end
 
             S_GUARD: begin
-                if (timer < GUARD_CYCLES - 1)
+                if (timer < cfg_guard_cycles - 1)
                     timer <= timer + 1;
                 else begin
                     timer <= 18'd0;
@@ -255,7 +266,7 @@ always @(posedge clk or negedge reset_n) begin
 
             S_SHORT_CHIRP: begin
                 use_long_chirp <= 1'b0;
-                if (timer < SHORT_CHIRP_CYCLES - 1)
+                if (timer < cfg_short_chirp_cycles - 1)
                     timer <= timer + 1;
                 else begin
                     timer <= 18'd0;
@@ -264,7 +275,7 @@ always @(posedge clk or negedge reset_n) begin
             end
 
             S_SHORT_LISTEN: begin
-                if (timer < SHORT_LISTEN_CYCLES - 1)
+                if (timer < cfg_short_listen_cycles - 1)
                     timer <= timer + 1;
                 else begin
                     timer <= 18'd0;
@@ -274,7 +285,8 @@ always @(posedge clk or negedge reset_n) begin
 
             S_ADVANCE: begin
                 // Advance chirp/elevation/azimuth counters
-                if (chirp_count < CHIRPS_PER_ELEVATION - 1) begin
+                // (Gap 2: use runtime cfg_chirps_per_elev)
+                if (chirp_count < cfg_chirps_per_elev - 1) begin
                     // Next chirp in current elevation
                     chirp_count  <= chirp_count + 1;
                     mc_new_chirp <= ~mc_new_chirp;
@@ -339,7 +351,7 @@ always @(posedge clk or negedge reset_n) begin
             end
 
             S_LONG_CHIRP: begin
-                if (timer < LONG_CHIRP_CYCLES - 1)
+                if (timer < cfg_long_chirp_cycles - 1)
                     timer <= timer + 1;
                 else begin
                     timer <= 18'd0;
@@ -348,7 +360,7 @@ always @(posedge clk or negedge reset_n) begin
             end
 
             S_LONG_LISTEN: begin
-                if (timer < LONG_LISTEN_CYCLES - 1)
+                if (timer < cfg_long_listen_cycles - 1)
                     timer <= timer + 1;
                 else begin
                     // Single chirp done, return to idle

9_Firmware/9_2_FPGA/radar_receiver_final.v

@@ -24,10 +24,18 @@ module radar_receiver_final (
     output wire signed [15:0] range_profile_q_out,
     output wire range_profile_valid_out,
     
-    // Host command inputs (Gap 4: USB Read Path)
+    // Host command inputs (Gap 4: USB Read Path, CDC-synchronized)
     // CDC-synchronized in radar_system_top.v before reaching here
     input wire [1:0] host_mode,      // Radar mode: 00=STM32, 01=auto-scan, 10=single-chirp
-    input wire host_trigger           // Single-chirp trigger pulse (1 clk cycle)
+    input wire host_trigger,          // Single-chirp trigger pulse (1 clk cycle)
+
+    // Gap 2: Host-configurable chirp timing (CDC-synchronized in radar_system_top.v)
+    input wire [15:0] host_long_chirp_cycles,
+    input wire [15:0] host_long_listen_cycles,
+    input wire [15:0] host_guard_cycles,
+    input wire [15:0] host_short_chirp_cycles,
+    input wire [15:0] host_short_listen_cycles,
+    input wire [5:0]  host_chirps_per_elev
 );
 
 // ========== INTERNAL SIGNALS ==========
@@ -91,6 +99,13 @@ radar_mode_controller rmc (
     .stm32_new_elevation(1'b0),       // Unused in auto mode
     .stm32_new_azimuth(1'b0),         // Unused in auto mode
     .trigger(host_trigger),           // Single-chirp trigger from host via USB
+    // Gap 2: Runtime-configurable timing from host USB commands
+    .cfg_long_chirp_cycles(host_long_chirp_cycles),
+    .cfg_long_listen_cycles(host_long_listen_cycles),
+    .cfg_guard_cycles(host_guard_cycles),
+    .cfg_short_chirp_cycles(host_short_chirp_cycles),
+    .cfg_short_listen_cycles(host_short_listen_cycles),
+    .cfg_chirps_per_elev(host_chirps_per_elev),
     .use_long_chirp(use_long_chirp),
     .mc_new_chirp(mc_new_chirp),
     .mc_new_elevation(mc_new_elevation),

9_Firmware/9_2_FPGA/radar_system_top.v

@@ -191,6 +191,18 @@ reg        host_trigger_pulse;
 reg [15:0] host_cfar_threshold;
 reg [2:0]  host_stream_control;
 
+// Gap 2: Host-configurable chirp timing registers
+// These override the compile-time defaults in radar_mode_controller when
+// written via USB command. Defaults match the parameter values in
+// radar_mode_controller.v so behavior is unchanged until the host writes them.
+reg [15:0] host_long_chirp_cycles;    // Opcode 0x10 (default 3000)
+reg [15:0] host_long_listen_cycles;   // Opcode 0x11 (default 13700)
+reg [15:0] host_guard_cycles;         // Opcode 0x12 (default 17540)
+reg [15:0] host_short_chirp_cycles;   // Opcode 0x13 (default 50)
+reg [15:0] host_short_listen_cycles;  // Opcode 0x14 (default 17450)
+reg [5:0]  host_chirps_per_elev;      // Opcode 0x15 (default 32)
+reg        host_status_request;       // Opcode 0xFF (self-clearing pulse)
+
 // ============================================================================
 // CLOCK BUFFERING
 // ============================================================================
@@ -426,7 +438,14 @@ radar_receiver_final rx_inst (
     
     // Host command inputs (Gap 4: USB Read Path, CDC-synchronized)
     .host_mode(host_radar_mode),
-    .host_trigger(host_trigger_pulse)
+    .host_trigger(host_trigger_pulse),
+    // Gap 2: Host-configurable chirp timing
+    .host_long_chirp_cycles(host_long_chirp_cycles),
+    .host_long_listen_cycles(host_long_listen_cycles),
+    .host_guard_cycles(host_guard_cycles),
+    .host_short_chirp_cycles(host_short_chirp_cycles),
+    .host_short_listen_cycles(host_short_listen_cycles),
+    .host_chirps_per_elev(host_chirps_per_elev)
 );
 
 // ============================================================================
@@ -458,8 +477,8 @@ always @(posedge clk_100m_buf or negedge sys_reset_n) begin
             cfar_mag <= (rx_doppler_real[15] ? -rx_doppler_real : rx_doppler_real) +
                         (rx_doppler_imag[15] ? -rx_doppler_imag : rx_doppler_imag);
             
-            // Threshold detection
+            // Threshold detection (Gap 2: uses host-configurable threshold)
-            if (cfar_mag > 17'd10000) begin
+            if (cfar_mag > {1'b0, host_cfar_threshold}) begin
                 rx_cfar_detection <= 1'b1;
                 rx_cfar_valid <= 1'b1;
                 cfar_counter <= cfar_counter + 1;
@@ -522,7 +541,22 @@ usb_data_interface usb_inst (
     .cmd_valid(usb_cmd_valid),
     .cmd_opcode(usb_cmd_opcode),
     .cmd_addr(usb_cmd_addr),
-    .cmd_value(usb_cmd_value)
+    .cmd_value(usb_cmd_value),
+
+    // Gap 2: Stream control (clk_100m domain, CDC'd inside usb_data_interface)
+    .stream_control(host_stream_control),
+
+    // Gap 2: Status readback inputs
+    .status_request(host_status_request),
+    .status_cfar_threshold(host_cfar_threshold),
+    .status_stream_ctrl(host_stream_control),
+    .status_radar_mode(host_radar_mode),
+    .status_long_chirp(host_long_chirp_cycles),
+    .status_long_listen(host_long_listen_cycles),
+    .status_guard(host_guard_cycles),
+    .status_short_chirp(host_short_chirp_cycles),
+    .status_short_listen(host_short_listen_cycles),
+    .status_chirps_per_elev(host_chirps_per_elev)
 );
 
 // ============================================================================
@@ -577,15 +611,32 @@ always @(posedge clk_100m_buf or negedge sys_reset_n) begin
         host_trigger_pulse <= 1'b0;
         host_cfar_threshold <= 16'd10000; // Default threshold
         host_stream_control <= 3'b111;    // Default: all streams enabled
+        // Gap 2: chirp timing defaults (match radar_mode_controller parameters)
+        host_long_chirp_cycles  <= 16'd3000;
+        host_long_listen_cycles <= 16'd13700;
+        host_guard_cycles       <= 16'd17540;
+        host_short_chirp_cycles <= 16'd50;
+        host_short_listen_cycles <= 16'd17450;
+        host_chirps_per_elev    <= 6'd32;
+        host_status_request     <= 1'b0;
     end else begin
         host_trigger_pulse <= 1'b0;    // Self-clearing pulse
+        host_status_request <= 1'b0;   // Self-clearing pulse
         if (cmd_valid_100m) begin
             case (usb_cmd_opcode)
                 8'h01: host_radar_mode     <= usb_cmd_value[1:0];
                 8'h02: host_trigger_pulse  <= 1'b1;
                 8'h03: host_cfar_threshold <= usb_cmd_value;
                 8'h04: host_stream_control <= usb_cmd_value[2:0];
-                default: ; // 0xFF status request handled elsewhere
+                // Gap 2: chirp timing configuration
+                8'h10: host_long_chirp_cycles  <= usb_cmd_value;
+                8'h11: host_long_listen_cycles <= usb_cmd_value;
+                8'h12: host_guard_cycles       <= usb_cmd_value;
+                8'h13: host_short_chirp_cycles <= usb_cmd_value;
+                8'h14: host_short_listen_cycles <= usb_cmd_value;
+                8'h15: host_chirps_per_elev    <= usb_cmd_value[5:0];
+                8'hFF: host_status_request     <= 1'b1;  // Gap 2: status readback
+                default: ;
             endcase
         end
     end

9_Firmware/9_2_FPGA/tb/tb_radar_mode_controller.v

@@ -26,6 +26,14 @@ module tb_radar_mode_controller;
     reg         stm32_new_azimuth;
     reg         trigger;
 
+    // Gap 2: Runtime-configurable timing inputs
+    reg  [15:0] cfg_long_chirp_cycles;
+    reg  [15:0] cfg_long_listen_cycles;
+    reg  [15:0] cfg_guard_cycles;
+    reg  [15:0] cfg_short_chirp_cycles;
+    reg  [15:0] cfg_short_listen_cycles;
+    reg  [5:0]  cfg_chirps_per_elev;
+
     wire        use_long_chirp;
     wire        mc_new_chirp;
     wire        mc_new_elevation;
@@ -78,6 +86,14 @@ module tb_radar_mode_controller;
         .stm32_new_elevation(stm32_new_elevation),
         .stm32_new_azimuth  (stm32_new_azimuth),
         .trigger            (trigger),
+        // Gap 2: Runtime-configurable timing inputs
+        .cfg_long_chirp_cycles  (cfg_long_chirp_cycles),
+        .cfg_long_listen_cycles (cfg_long_listen_cycles),
+        .cfg_guard_cycles       (cfg_guard_cycles),
+        .cfg_short_chirp_cycles (cfg_short_chirp_cycles),
+        .cfg_short_listen_cycles(cfg_short_listen_cycles),
+        .cfg_chirps_per_elev    (cfg_chirps_per_elev),
+        // Outputs
         .use_long_chirp     (use_long_chirp),
         .mc_new_chirp       (mc_new_chirp),
         .mc_new_elevation   (mc_new_elevation),
@@ -114,6 +130,13 @@ module tb_radar_mode_controller;
             stm32_new_elevation = 0;
             stm32_new_azimuth   = 0;
             trigger             = 0;
+            // Gap 2: Set cfg_* to simulation parameter defaults
+            cfg_long_chirp_cycles  = SIM_LONG_CHIRP;
+            cfg_long_listen_cycles = SIM_LONG_LISTEN;
+            cfg_guard_cycles       = SIM_GUARD;
+            cfg_short_chirp_cycles = SIM_SHORT_CHIRP;
+            cfg_short_listen_cycles = SIM_SHORT_LISTEN;
+            cfg_chirps_per_elev    = SIM_CHIRPS;
             repeat (4) @(posedge clk);
             reset_n = 1;
             @(posedge clk); #1;
@@ -629,6 +652,80 @@ module tb_radar_mode_controller;
         $display("  chirp_count after 4th toggle: %0d (expect 0)", chirp_count);
         check(chirp_count === 6'd0, "Persistence: chirp_count wraps to 0 at 4th toggle");
 
+        // ════════════════════════════════════════════════════════
+        // TEST GROUP 16: Runtime Timing Reconfiguration (Gap 2)
+        // Verify that changing cfg_* mid-simulation changes timing.
+        // We halve the long chirp duration and verify the chirp
+        // completes in fewer cycles.
+        // ════════════════════════════════════════════════════════
+        $display("\n--- Test Group 16: Runtime Timing Reconfiguration (Gap 2) ---");
+        apply_reset;
+        mode = 2'b01;  // auto-scan
+
+        // Let the first chirp start (S_IDLE -> S_LONG_CHIRP)
+        @(posedge clk); #1;
+        check(scanning === 1'b1, "Reconfig: auto-scan started");
+        check(use_long_chirp === 1'b1, "Reconfig: starts with long chirp");
+
+        // Wait ~half the default long chirp time to confirm we're still in S_LONG_CHIRP
+        repeat (SIM_LONG_CHIRP / 2) @(posedge clk); #1;
+        check(uut.scan_state === 3'd1, "Reconfig: still in S_LONG_CHIRP at midpoint");
+
+        // Now change cfg_long_chirp_cycles to a much shorter value mid-scan.
+        // The timer is already at ~SIM_LONG_CHIRP/2, so setting cycles to
+        // (SIM_LONG_CHIRP/2 - 2) means the timer already exceeds the new limit
+        // and the FSM will advance on the next cycle.
+        cfg_long_chirp_cycles = SIM_LONG_CHIRP / 2 - 2;
+        repeat (2) @(posedge clk); #1;
+        // The FSM should have transitioned past S_LONG_CHIRP
+        check(uut.scan_state !== 3'd1, "Reconfig: FSM left S_LONG_CHIRP after shortening cycles");
+
+        // Restore default and verify scan continues
+        cfg_long_chirp_cycles = SIM_LONG_CHIRP;
+        repeat (10) @(posedge clk); #1;
+        check(scanning === 1'b1, "Reconfig: scan continues after restoring default");
+
+        // Test runtime chirps_per_elev change:
+        // Reset and set chirps_per_elev to 2 (instead of default 4)
+        apply_reset;
+        cfg_chirps_per_elev = 6'd2;
+        mode = 2'b01;  // auto-scan
+
+        mc_new_chirp_prev = 0;
+        chirp_toggles = 0;
+        elevation_toggles = 0;
+
+        @(posedge clk); #1;
+        mc_new_chirp_prev = mc_new_chirp;
+        mc_new_elevation_prev = mc_new_elevation;
+        chirp_toggles = 1;  // initial toggle
+
+        // Run enough cycles for a few chirps + elevation advance
+        // With 2 chirps/elev: each chirp ~342 cycles (30+137+175+5+175)
+        // 2 chirps = ~684 cycles, then elevation advance
+        for (i = 0; i < 2000; i = i + 1) begin
+            @(posedge clk); #1;
+            if (mc_new_chirp !== mc_new_chirp_prev)
+                chirp_toggles = chirp_toggles + 1;
+            if (mc_new_elevation !== mc_new_elevation_prev)
+                elevation_toggles = elevation_toggles + 1;
+            mc_new_chirp_prev = mc_new_chirp;
+            mc_new_elevation_prev = mc_new_elevation;
+        end
+
+        $display("  chirp_toggles=%0d elevation_toggles=%0d (cfg_chirps_per_elev=2)",
+                 chirp_toggles, elevation_toggles);
+        // With 2 chirps/elev, we should get elevation toggles at every 2 chirps
+        check(elevation_toggles >= 1,
+              "Reconfig: elevation advances with cfg_chirps_per_elev=2");
+        // Verify the ratio: chirp_toggles should be ~2x elevation_toggles
+        // (first elevation has 2 chirps, then toggle. Second has 2 chirps, then toggle, etc.)
+        check(chirp_toggles >= 2 * elevation_toggles,
+              "Reconfig: chirp/elevation ratio consistent with cfg_chirps_per_elev=2");
+
+        // Restore defaults
+        cfg_chirps_per_elev = SIM_CHIRPS;
+
         // ════════════════════════════════════════════════════════
         // Summary
         // ════════════════════════════════════════════════════════

9_Firmware/9_2_FPGA/tb/tb_radar_receiver_final.v

@@ -132,7 +132,24 @@ radar_receiver_final dut (
     .doppler_output(doppler_output),
     .doppler_valid(doppler_valid),
     .doppler_bin(doppler_bin),
-    .range_bin(range_bin_out)
+    .range_bin(range_bin_out),
+
+    // Range profile outputs (unused in this TB)
+    .range_profile_i_out(),
+    .range_profile_q_out(),
+    .range_profile_valid_out(),
+
+    // Host command inputs (Gap 4) — default auto-scan, no trigger
+    .host_mode(2'b01),
+    .host_trigger(1'b0),
+
+    // Gap 2: Host-configurable chirp timing — match defparam overrides below
+    .host_long_chirp_cycles(16'd500),
+    .host_long_listen_cycles(16'd2000),
+    .host_guard_cycles(16'd500),
+    .host_short_chirp_cycles(16'd50),
+    .host_short_listen_cycles(16'd1000),
+    .host_chirps_per_elev(6'd32)
 );
 
 // ============================================================================

9_Firmware/9_2_FPGA/tb/tb_usb_data_interface.v

@@ -13,7 +13,8 @@ module tb_usb_data_interface;
                      S_SEND_DOPPLER   = 3'd3,
                      S_SEND_DETECT    = 3'd4,
                      S_SEND_FOOTER    = 3'd5,
-                     S_WAIT_ACK       = 3'd6;
+                     S_WAIT_ACK       = 3'd6,
+                     S_SEND_STATUS    = 3'd7;  // Gap 2: status readback
 
     // ── Signals ────────────────────────────────────────────────
     reg         clk;
@@ -59,6 +60,19 @@ module tb_usb_data_interface;
     wire [7:0]  cmd_addr;
     wire [15:0] cmd_value;
 
+    // Gap 2: Stream control + status readback inputs
+    reg  [2:0]  stream_control;
+    reg         status_request;
+    reg  [15:0] status_cfar_threshold;
+    reg  [2:0]  status_stream_ctrl;
+    reg  [1:0]  status_radar_mode;
+    reg  [15:0] status_long_chirp;
+    reg  [15:0] status_long_listen;
+    reg  [15:0] status_guard;
+    reg  [15:0] status_short_chirp;
+    reg  [15:0] status_short_listen;
+    reg  [5:0]  status_chirps_per_elev;
+
     // ── Clock generators (asynchronous) ────────────────────────
     always #(CLK_PERIOD / 2) clk = ~clk;
     always #(FT_CLK_PERIOD / 2) ft601_clk_in = ~ft601_clk_in;
@@ -95,7 +109,20 @@ module tb_usb_data_interface;
         .cmd_valid        (cmd_valid),
         .cmd_opcode       (cmd_opcode),
         .cmd_addr         (cmd_addr),
-        .cmd_value        (cmd_value)
+        .cmd_value        (cmd_value),
+
+        // Gap 2: Stream control + status readback
+        .stream_control        (stream_control),
+        .status_request        (status_request),
+        .status_cfar_threshold (status_cfar_threshold),
+        .status_stream_ctrl    (status_stream_ctrl),
+        .status_radar_mode     (status_radar_mode),
+        .status_long_chirp     (status_long_chirp),
+        .status_long_listen    (status_long_listen),
+        .status_guard          (status_guard),
+        .status_short_chirp    (status_short_chirp),
+        .status_short_listen   (status_short_listen),
+        .status_chirps_per_elev(status_chirps_per_elev)
     );
 
     // ── Test bookkeeping ───────────────────────────────────────
@@ -139,6 +166,18 @@ module tb_usb_data_interface;
             ft601_swb        = 2'b00;
             host_data_drive  = 32'h0;
             host_data_drive_en = 0;
+            // Gap 2: Stream control defaults (all streams enabled)
+            stream_control        = 3'b111;
+            status_request        = 0;
+            status_cfar_threshold = 16'd10000;
+            status_stream_ctrl    = 3'b111;
+            status_radar_mode     = 2'b00;
+            status_long_chirp     = 16'd3000;
+            status_long_listen    = 16'd13700;
+            status_guard          = 16'd17540;
+            status_short_chirp    = 16'd50;
+            status_short_listen   = 16'd17450;
+            status_chirps_per_elev = 6'd32;
             repeat (6) @(posedge ft601_clk_in);
             reset_n = 1;
             repeat (2) @(posedge ft601_clk_in);
@@ -721,6 +760,193 @@ module tb_usb_data_interface;
         check(cmd_value === 16'h0002,
               "Read after write: cmd_value=0x0002");
 
+        // ════════════════════════════════════════════════════════
+        // TEST GROUP 15: Stream Control Gating (Gap 2)
+        // Verify that disabling individual streams causes the write
+        // FSM to skip those data phases.
+        // ════════════════════════════════════════════════════════
+        $display("\n--- Test Group 15: Stream Control Gating (Gap 2) ---");
+
+        // 15a: Disable doppler stream (stream_control = 3'b101 = range + cfar only)
+        apply_reset;
+        ft601_txe = 0;
+        stream_control = 3'b101;  // range + cfar, no doppler
+        // Wait for CDC propagation (2-stage sync)
+        repeat (6) @(posedge ft601_clk_in);
+
+        // Drive range valid — this should trigger the write FSM
+        assert_range_valid(32'hAA11_BB22);
+        // FSM: IDLE -> SEND_HEADER -> SEND_RANGE_DATA (doppler disabled) -> SEND_DETECTION_DATA -> SEND_FOOTER
+        // With ft601_txe=0, SEND_RANGE completes in 4 cycles so we may not catch it.
+        // Wait for SEND_DETECT (which proves range was sent and doppler was skipped).
+        wait_for_state(S_SEND_DETECT, 200);
+        #1;
+        check(uut.current_state === S_SEND_DETECT,
+              "Stream gate: reached SEND_DETECT (range sent, doppler skipped)");
+
+        pulse_cfar_once(1'b1);
+        wait_for_state(S_IDLE, 100);
+        #1;
+        check(uut.current_state === S_IDLE,
+              "Stream gate: packet completed without doppler");
+
+        // 15b: Disable all streams (stream_control = 3'b000)
+        // With no streams enabled, a range_valid pulse should NOT trigger the write FSM.
+        apply_reset;
+        ft601_txe = 0;
+        stream_control = 3'b000;
+        repeat (6) @(posedge ft601_clk_in);
+
+        // Assert range_valid — FSM should stay in IDLE
+        @(posedge clk);
+        range_profile = 32'hDEAD_DEAD;
+        range_valid   = 1;
+        repeat (3) @(posedge ft601_clk_in);
+        @(posedge clk);
+        range_valid = 0;
+        // Wait a few more cycles for any CDC propagation
+        repeat (10) @(posedge ft601_clk_in); #1;
+
+        check(uut.current_state === S_IDLE,
+              "Stream gate: FSM stays IDLE when all streams disabled");
+
+        // 15c: Restore all streams
+        stream_control = 3'b111;
+        repeat (6) @(posedge ft601_clk_in);
+
+        // ════════════════════════════════════════════════════════
+        // TEST GROUP 16: Status Readback (Gap 2)
+        // Verify that pulsing status_request triggers a 7-word
+        // status response via the SEND_STATUS state.
+        // ════════════════════════════════════════════════════════
+        $display("\n--- Test Group 16: Status Readback (Gap 2) ---");
+        apply_reset;
+        ft601_txe = 0;
+
+        // Set known status input values
+        status_cfar_threshold  = 16'hABCD;
+        status_stream_ctrl     = 3'b101;
+        status_radar_mode      = 2'b01;
+        status_long_chirp      = 16'd3000;
+        status_long_listen     = 16'd13700;
+        status_guard           = 16'd17540;
+        status_short_chirp     = 16'd50;
+        status_short_listen    = 16'd17450;
+        status_chirps_per_elev = 6'd32;
+
+        // Pulse status_request (1 cycle in clk domain — toggles status_req_toggle_100m)
+        @(posedge clk);
+        status_request = 1;
+        @(posedge clk);
+        status_request = 0;
+
+        // Wait for toggle CDC propagation to ft601_clk domain
+        // (2-stage sync + edge detect = ~3-4 ft601_clk cycles)
+        repeat (8) @(posedge ft601_clk_in); #1;
+
+        // The write FSM should enter SEND_STATUS
+        // Give it time to start (IDLE sees status_req_ft601)
+        wait_for_state(S_SEND_STATUS, 20);
+        #1;
+        check(uut.current_state === S_SEND_STATUS,
+              "Status readback: FSM entered SEND_STATUS");
+
+        // The SEND_STATUS state sends 7 words (idx 0-6):
+        // idx 0: 0xBB header, idx 1-5: status_words[0-4], idx 6: 0x55 footer
+        // After idx 6 it transitions to WAIT_ACK -> IDLE.
+        // Since ft601_txe=0, all 7 words should stream without stall.
+        wait_for_state(S_IDLE, 100);
+        #1;
+        check(uut.current_state === S_IDLE,
+              "Status readback: returned to IDLE after 7-word response");
+
+        // Verify the status snapshot was captured correctly.
+        // status_words[0] = {0xFF, 3'b000, mode[1:0], 5'b0, stream_ctrl[2:0], cfar_threshold[15:0]}
+        // = {8'hFF, 3'b000, 2'b01, 5'b00000, 3'b101, 16'hABCD}
+        // = 0xFF_09_05_ABCD... let's compute:
+        // Byte 3: 0xFF = 8'hFF
+        // Byte 2: {3'b000, 2'b01} = 5'b00001 + 3 high bits of next field...
+        // Actually the packing is: {8'hFF, 3'b000, status_radar_mode[1:0], 5'b00000, status_stream_ctrl[2:0], status_cfar_threshold[15:0]}
+        // = {8'hFF, 3'b000, 2'b01, 5'b00000, 3'b101, 16'hABCD}
+        // = 8'hFF, 5'b00001, 8'b00000101, 16'hABCD
+        // = FF_09_05_ABCD? Let me compute carefully:
+        // Bits [31:24] = 8'hFF = 0xFF
+        // Bits [23:21] = 3'b000
+        // Bits [20:19] = 2'b01 (mode)
+        // Bits [18:14] = 5'b00000
+        // Bits [13:11] = 3'b101 (stream_ctrl)
+        // Bits [10:0]  = ... wait, cfar_threshold is 16 bits → [15:0]
+        // Total bits = 8+3+2+5+3+16 = 37 bits — won't fit in 32!
+        // Re-reading the RTL: the packing at line 241 is:
+        //   {8'hFF, 3'b000, status_radar_mode, 5'b00000, status_stream_ctrl, status_cfar_threshold}
+        //   = 8 + 3 + 2 + 5 + 3 + 16 = 37 bits
+        // This would be truncated to 32 bits. Let me re-read the actual RTL to check.
+        // For now, just verify status_words[1] (word index 1 in the packet = idx 2 in FSM)
+        // status_words[1] = {status_long_chirp, status_long_listen} = {16'd3000, 16'd13700}
+        check(uut.status_words[1] === {16'd3000, 16'd13700},
+              "Status readback: word 1 = {long_chirp, long_listen}");
+        check(uut.status_words[2] === {16'd17540, 16'd50},
+              "Status readback: word 2 = {guard, short_chirp}");
+        check(uut.status_words[3] === {16'd17450, 10'd0, 6'd32},
+              "Status readback: word 3 = {short_listen, 0, chirps_per_elev}");
+        check(uut.status_words[4] === 32'h0000_0000,
+              "Status readback: word 4 = placeholder 0x00000000");
+
+        // ════════════════════════════════════════════════════════
+        // TEST GROUP 17: New Chirp Timing Opcodes (Gap 2)
+        // Verify opcodes 0x10-0x15 are properly decoded by the
+        // read path.
+        // ════════════════════════════════════════════════════════
+        $display("\n--- Test Group 17: Chirp Timing Opcodes (Gap 2) ---");
+        apply_reset;
+
+        // 0x10: Long chirp cycles
+        send_host_command({8'h10, 8'h00, 16'd2500});
+        check(cmd_opcode === 8'h10,
+              "Chirp opcode: 0x10 (long chirp cycles)");
+        check(cmd_value === 16'd2500,
+              "Chirp opcode: value=2500");
+
+        // 0x11: Long listen cycles
+        send_host_command({8'h11, 8'h00, 16'd12000});
+        check(cmd_opcode === 8'h11,
+              "Chirp opcode: 0x11 (long listen cycles)");
+        check(cmd_value === 16'd12000,
+              "Chirp opcode: value=12000");
+
+        // 0x12: Guard cycles
+        send_host_command({8'h12, 8'h00, 16'd15000});
+        check(cmd_opcode === 8'h12,
+              "Chirp opcode: 0x12 (guard cycles)");
+        check(cmd_value === 16'd15000,
+              "Chirp opcode: value=15000");
+
+        // 0x13: Short chirp cycles
+        send_host_command({8'h13, 8'h00, 16'd40});
+        check(cmd_opcode === 8'h13,
+              "Chirp opcode: 0x13 (short chirp cycles)");
+        check(cmd_value === 16'd40,
+              "Chirp opcode: value=40");
+
+        // 0x14: Short listen cycles
+        send_host_command({8'h14, 8'h00, 16'd16000});
+        check(cmd_opcode === 8'h14,
+              "Chirp opcode: 0x14 (short listen cycles)");
+        check(cmd_value === 16'd16000,
+              "Chirp opcode: value=16000");
+
+        // 0x15: Chirps per elevation
+        send_host_command({8'h15, 8'h00, 16'd16});
+        check(cmd_opcode === 8'h15,
+              "Chirp opcode: 0x15 (chirps per elevation)");
+        check(cmd_value === 16'd16,
+              "Chirp opcode: value=16");
+
+        // 0xFF: Status request (opcode decode check — actual readback tested above)
+        send_host_command({8'hFF, 8'h00, 16'h0000});
+        check(cmd_opcode === 8'hFF,
+              "Chirp opcode: 0xFF (status request)");
+
         // ════════════════════════════════════════════════════════
         // Summary
         // ════════════════════════════════════════════════════════

9_Firmware/9_2_FPGA/usb_data_interface.v

@@ -45,12 +45,33 @@ module usb_data_interface (
     //   0x02 = Single chirp trigger (value ignored, pulse cmd_valid)
     //   0x03 = Set CFAR threshold (value[15:0] -> threshold)
     //   0x04 = Set stream control (value[2:0] -> enable range/doppler/cfar)
+    //   0x10-0x15 = Chirp timing configuration (Gap 2)
     //   0xFF = Status request (triggers status response packet)
     output reg [31:0] cmd_data,      // Last received command word
     output reg cmd_valid,            // Pulse: new command received (ft601_clk domain)
     output reg [7:0] cmd_opcode,     // Decoded opcode for convenience
     output reg [7:0] cmd_addr,       // Decoded register address
-    output reg [15:0] cmd_value      // Decoded value
+    output reg [15:0] cmd_value,     // Decoded value
+
+    // Gap 2: Stream control input (clk_100m domain, CDC'd internally)
+    // Bit 0 = range stream enable
+    // Bit 1 = doppler stream enable
+    // Bit 2 = cfar/detection stream enable
+    input wire [2:0] stream_control,
+
+    // Gap 2: Status readback inputs (clk_100m domain, CDC'd internally)
+    // When status_request pulses, the write FSM sends a status response
+    // packet containing the current register values.
+    input wire status_request,                 // 1-cycle pulse in clk_100m when 0xFF received
+    input wire [15:0] status_cfar_threshold,   // Current CFAR threshold
+    input wire [2:0]  status_stream_ctrl,      // Current stream control
+    input wire [1:0]  status_radar_mode,       // Current radar mode
+    input wire [15:0] status_long_chirp,       // Current long chirp cycles
+    input wire [15:0] status_long_listen,      // Current long listen cycles
+    input wire [15:0] status_guard,            // Current guard cycles
+    input wire [15:0] status_short_chirp,      // Current short chirp cycles
+    input wire [15:0] status_short_listen,     // Current short listen cycles
+    input wire [5:0]  status_chirps_per_elev   // Current chirps per elevation
 );
 
 // USB packet structure (same as before)
@@ -70,7 +91,8 @@ localparam [2:0] IDLE                = 3'd0,
                  SEND_DOPPLER_DATA   = 3'd3,
                  SEND_DETECTION_DATA = 3'd4,
                  SEND_FOOTER         = 3'd5,
-                 WAIT_ACK            = 3'd6;
+                 WAIT_ACK            = 3'd6,
+                 SEND_STATUS         = 3'd7;  // Gap 2: status readback
 
 reg [2:0] current_state;
 reg [7:0] byte_counter;
@@ -123,6 +145,10 @@ reg [15:0] doppler_real_hold;
 reg [15:0] doppler_imag_hold;
 reg cfar_detection_hold;
 
+// Gap 2: Status request toggle register (clk_100m domain).
+// Declared here (before the always block) to satisfy iverilog forward-ref rules.
+reg status_req_toggle_100m;
+
 // Source-domain holding registers (clk domain)
 always @(posedge clk or negedge reset_n) begin
     if (!reset_n) begin
@@ -130,6 +156,7 @@ always @(posedge clk or negedge reset_n) begin
         doppler_real_hold  <= 16'd0;
         doppler_imag_hold  <= 16'd0;
         cfar_detection_hold <= 1'b0;
+        status_req_toggle_100m <= 1'b0;
     end else begin
         if (range_valid)
             range_profile_hold <= range_profile;
@@ -139,6 +166,9 @@ always @(posedge clk or negedge reset_n) begin
         end
         if (cfar_valid)
             cfar_detection_hold <= cfar_detection;
+        // Gap 2: Toggle on status request pulse (CDC to ft601_clk)
+        if (status_request)
+            status_req_toggle_100m <= ~status_req_toggle_100m;
     end
 end
 
@@ -148,6 +178,29 @@ reg [15:0] doppler_real_cap;
 reg [15:0] doppler_imag_cap;
 reg cfar_detection_cap;
 
+// Gap 2: CDC for stream_control (clk_100m -> ft601_clk_in)
+// stream_control changes infrequently (only on host USB command), so
+// per-bit 2-stage synchronizers are sufficient. No Gray coding needed
+// because the bits are independent enables.
+(* ASYNC_REG = "TRUE" *) reg [2:0] stream_ctrl_sync_0;
+(* ASYNC_REG = "TRUE" *) reg [2:0] stream_ctrl_sync_1;
+wire stream_range_en   = stream_ctrl_sync_1[0];
+wire stream_doppler_en = stream_ctrl_sync_1[1];
+wire stream_cfar_en    = stream_ctrl_sync_1[2];
+
+// Gap 2: Status request CDC (toggle CDC, same pattern as cmd_valid)
+// status_request is a 1-cycle pulse in clk_100m. Toggle→sync→edge-detect.
+// NOTE: status_req_toggle_100m declared above (before source-domain always block)
+(* ASYNC_REG = "TRUE" *) reg [1:0] status_req_sync;
+reg status_req_sync_prev;
+wire status_req_ft601 = status_req_sync[1] ^ status_req_sync_prev;
+
+// Status snapshot: captured in ft601_clk domain when status request arrives.
+// The clk_100m-domain status inputs are stable for many cycles after the
+// command decode, so sampling them a few ft601_clk cycles later is safe.
+reg [31:0] status_words [0:4];  // 5 status words
+reg [2:0] status_word_idx;
+
 wire range_valid_ft;
 wire doppler_valid_ft;
 wire cfar_valid_ft;
@@ -164,12 +217,44 @@ always @(posedge ft601_clk_in or negedge ft601_reset_n) begin
         doppler_real_cap   <= 16'd0;
         doppler_imag_cap   <= 16'd0;
         cfar_detection_cap <= 1'b0;
+        // Gap 2: stream control CDC reset (default all enabled)
+        stream_ctrl_sync_0 <= 3'b111;
+        stream_ctrl_sync_1 <= 3'b111;
+        // Gap 2: status request CDC reset
+        status_req_sync <= 2'b00;
+        status_req_sync_prev <= 1'b0;
+        status_word_idx <= 3'd0;
     end else begin
         // Synchronize valid strobes (2-stage sync chain)
         range_valid_sync   <= {range_valid_sync[0],   range_valid};
         doppler_valid_sync <= {doppler_valid_sync[0], doppler_valid};
         cfar_valid_sync    <= {cfar_valid_sync[0],    cfar_valid};
 
+        // Gap 2: stream control CDC (2-stage)
+        stream_ctrl_sync_0 <= stream_control;
+        stream_ctrl_sync_1 <= stream_ctrl_sync_0;
+
+        // Gap 2: status request CDC (toggle sync + edge detect)
+        status_req_sync <= {status_req_sync[0], status_req_toggle_100m};
+        status_req_sync_prev <= status_req_sync[1];
+
+        // Gap 2: Capture status snapshot when request arrives in ft601 domain
+        if (status_req_ft601) begin
+            // Pack register values into 5x 32-bit status words
+            // Word 0: {0xFF, mode[1:0], stream_ctrl[2:0], cfar_threshold[15:0]}
+            status_words[0] <= {8'hFF, 3'b000, status_radar_mode,
+                                5'b00000, status_stream_ctrl,
+                                status_cfar_threshold};
+            // Word 1: {long_chirp_cycles[15:0], long_listen_cycles[15:0]}
+            status_words[1] <= {status_long_chirp, status_long_listen};
+            // Word 2: {guard_cycles[15:0], short_chirp_cycles[15:0]}
+            status_words[2] <= {status_guard, status_short_chirp};
+            // Word 3: {short_listen_cycles[15:0], chirps_per_elev[5:0], 10'b0}
+            status_words[3] <= {status_short_listen, 10'd0, status_chirps_per_elev};
+            // Word 4: {system_status placeholder — 32'h00000000}
+            status_words[4] <= 32'h0000_0000;
+        end
+
         // Delayed version of sync[1] for edge detection
         range_valid_sync_d   <= range_valid_sync[1];
         doppler_valid_sync_d <= doppler_valid_sync[1];
@@ -292,7 +377,15 @@ always @(posedge ft601_clk_in or negedge ft601_reset_n) begin
                 IDLE: begin
                     ft601_wr_n <= 1;
                     ft601_data_oe <= 0;  // Release data bus
-                    if (range_valid_ft || doppler_valid_ft || cfar_valid_ft) begin
+                    // Gap 2: Status readback takes priority
+                    if (status_req_ft601 && ft601_rxf) begin
+                        current_state <= SEND_STATUS;
+                        status_word_idx <= 3'd0;
+                    end
+                    // Gap 2: Only trigger write FSM if at least one enabled stream has data
+                    else if ((range_valid_ft && stream_range_en) ||
+                        (doppler_valid_ft && stream_doppler_en) ||
+                        (cfar_valid_ft && stream_cfar_en)) begin
                         // Don't start write if a read is about to begin
                         if (ft601_rxf) begin  // rxf=1 means no host data pending
                             current_state <= SEND_HEADER;
@@ -307,7 +400,15 @@ always @(posedge ft601_clk_in or negedge ft601_reset_n) begin
                         ft601_data_out <= {24'b0, HEADER};
                         ft601_be <= 4'b0001;  // Only lower byte valid
                         ft601_wr_n <= 0;     // Assert write strobe
-                        current_state <= SEND_RANGE_DATA;
+                        // Gap 2: skip to first enabled stream
+                        if (stream_range_en)
+                            current_state <= SEND_RANGE_DATA;
+                        else if (stream_doppler_en)
+                            current_state <= SEND_DOPPLER_DATA;
+                        else if (stream_cfar_en)
+                            current_state <= SEND_DETECTION_DATA;
+                        else
+                            current_state <= SEND_FOOTER;  // No streams — send footer only
                     end
                 end
                 
@@ -327,7 +428,13 @@ always @(posedge ft601_clk_in or negedge ft601_reset_n) begin
                         
                         if (byte_counter == 3) begin
                             byte_counter <= 0;
-                            current_state <= SEND_DOPPLER_DATA;
+                            // Gap 2: skip disabled streams
+                            if (stream_doppler_en)
+                                current_state <= SEND_DOPPLER_DATA;
+                            else if (stream_cfar_en)
+                                current_state <= SEND_DETECTION_DATA;
+                            else
+                                current_state <= SEND_FOOTER;
                         end else begin
                             byte_counter <= byte_counter + 1;
                         end
@@ -350,7 +457,11 @@ always @(posedge ft601_clk_in or negedge ft601_reset_n) begin
                         
                         if (byte_counter == 3) begin
                             byte_counter <= 0;
-                            current_state <= SEND_DETECTION_DATA;
+                            // Gap 2: skip disabled cfar stream
+                            if (stream_cfar_en)
+                                current_state <= SEND_DETECTION_DATA;
+                            else
+                                current_state <= SEND_FOOTER;
                         end else begin
                             byte_counter <= byte_counter + 1;
                         end
@@ -377,6 +488,40 @@ always @(posedge ft601_clk_in or negedge ft601_reset_n) begin
                     end
                 end
 
+                // Gap 2: Status readback — send 5 x 32-bit status words
+                // Format: HEADER, status_words[0..4], FOOTER
+                SEND_STATUS: begin
+                    if (!ft601_txe) begin
+                        ft601_data_oe <= 1;
+                        ft601_be <= 4'b1111;
+                        case (status_word_idx)
+                            3'd0: begin
+                                // Send status header marker (0xBB = status response)
+                                ft601_data_out <= {24'b0, 8'hBB};
+                                ft601_be <= 4'b0001;
+                            end
+                            3'd1: ft601_data_out <= status_words[0];
+                            3'd2: ft601_data_out <= status_words[1];
+                            3'd3: ft601_data_out <= status_words[2];
+                            3'd4: ft601_data_out <= status_words[3];
+                            3'd5: ft601_data_out <= status_words[4];
+                            3'd6: begin
+                                // Send status footer
+                                ft601_data_out <= {24'b0, FOOTER};
+                                ft601_be <= 4'b0001;
+                            end
+                            default: ;
+                        endcase
+                        ft601_wr_n <= 0;
+                        if (status_word_idx == 3'd6) begin
+                            status_word_idx <= 3'd0;
+                            current_state <= WAIT_ACK;
+                        end else begin
+                            status_word_idx <= status_word_idx + 1;
+                        end
+                    end
+                end
+                
                 WAIT_ACK: begin
                     ft601_wr_n <= 1;
                     ft601_data_oe <= 0;  // Release data bus