fix(display): no false display-detect on bare DevKit → CSI starves at MGMT-only (#1000) (#1121)

The SH8601 QSPI panel is write-only, so display_hal_init_panel() 'succeeds' even on a
bare display-less board — display_is_active() then returned true and main.c skipped the
#893/#906 MGMT->MGMT+DATA CSI filter upgrade (yield=0pps). Gate on the FT3168 touch I2C
readback (always present on the Touch-AMOLED board, absent on a bare DevKit): if touch is
absent, the panel 'success' was a false-positive — bail to headless before the display
task starts, so display_is_active() stays false and CSI captures.

Co-authored-by: ruv <ruvnet@gmail.com>

firmware/esp32-csi-node/main/display_task.c

@@ -114,6 +114,19 @@ esp_err_t display_task_start(void)
     /* Init touch (optional) */
     esp_err_t touch_ret = display_hal_init_touch();
 
+    /* The SH8601 QSPI panel is write-only — display_hal_init_panel() above "succeeds"
+     * even on a bare board with no panel attached, so it cannot detect absence. The
+     * FT3168 touch controller is an I2C device with readback and is always present on
+     * the Touch-AMOLED board. If touch is absent, the panel "success" was a false-
+     * positive on a display-less DevKit: bail to headless so display_is_active() stays
+     * false and CSI upgrades to MGMT+DATA capture instead of starving at MGMT-only
+     * (RuView#1000). */
+    if (touch_ret != ESP_OK) {
+        ESP_LOGW(TAG, "No FT3168 touch readback — SH8601 probe was a false-positive on a "
+                      "display-less board; running headless so CSI captures (#1000)");
+        return ESP_OK;
+    }
+
     /* Initialize LVGL */
     lv_init();
 

firmware/esp32-csi-node/main/mmwave_sensor.c

@@ -387,11 +387,21 @@ static mmwave_type_t probe_at_baud(uint32_t baud)
         if (len <= 0) continue;
 
         for (int i = 0; i < len; i++) {
-            /* MR60BHA2: SOF = 0x01, followed by valid-looking frame_id bytes */
-            if (buf[i] == MR60_SOF && baud == MMWAVE_MR60_BAUD) {
-                mr60_sof_seen++;
+            /* MR60BHA2: require a *validated* 8-byte header — SOF (0x01) + a valid
+             * header checksum (over bytes 0..6) + a known frame type (0x0A__ or
+             * 0x0F09) — NOT a bare 0x01 byte. A floating UART1 with no sensor reads
+             * noise full of 0x01s, which the old `buf[i] == MR60_SOF` check mistook
+             * for a real sensor (false "Detected MR60BHA2", #1107). */
+            if (buf[i] == MR60_SOF && baud == MMWAVE_MR60_BAUD && i + 7 < len) {
+                const uint8_t *h = &buf[i];
+                if (mr60_calc_checksum(h, 7) == h[7]) {
+                    uint16_t type = ((uint16_t)h[5] << 8) | h[6];
+                    if ((type >> 8) == 0x0A || type == 0x0F09) {
+                        mr60_sof_seen++;
+                    }
+                }
             }
-            /* LD2410: 4-byte header 0xF4F3F2F1 */
+            /* LD2410: 4-byte header 0xF4F3F2F1 (already specific enough). */
             if (i + 3 < len && buf[i] == 0xF4 && buf[i+1] == 0xF3
                 && buf[i+2] == 0xF2 && buf[i+3] == 0xF1
                 && baud == MMWAVE_LD2410_BAUD) {
@@ -403,9 +413,8 @@ static mmwave_type_t probe_at_baud(uint32_t baud)
         if (ld2410_header_seen >= 2) return MMWAVE_TYPE_LD2410;
     }
 
-    if (mr60_sof_seen > 0) return MMWAVE_TYPE_MR60BHA2;
-    if (ld2410_header_seen > 0) return MMWAVE_TYPE_LD2410;
-
+    /* No weak single-hit fallback: line noise can produce a stray match, so a real
+     * sensor must clear the ≥3 (MR60) / ≥2 (LD2410) validated-frame thresholds. */
     return MMWAVE_TYPE_NONE;
 }