feat: improve telemetry dashboard diagnostics

- Show top CRSF frame types received, by raw type byte,
  with a name lookup table (mirrors the Python tool)
- Send DEVICE_PING every 5s so DEVICE_INFO keeps appearing
  in the type breakdown
- Fix NO LINK status to trigger when uplink quality is 0
- Fix SNR display (drop erroneous extra -128 offset)
- Retry the initial DEVICE_INFO ping up to 3 times
- Probe 921600 baud before 400000/420000

tools/telemetry.c

@@ -17,7 +17,7 @@
 #endif
 
 /* Probe bauds: CP210x chips on ELRS can't hit 921600 exactly. */
-static int const s_probe_bauds[] = {400000, 420000, 921600};
+static int const s_probe_bauds[] = {921600, 400000, 420000};
 static int const s_probe_bauds_count =
     (int)(sizeof(s_probe_bauds) / sizeof(s_probe_bauds[0]));
 
@@ -88,9 +88,12 @@ typedef enum {
     STATUS_NO_SIGNAL
 } status_t;
 
-static status_t compute_status(double now, double link_t, double fc_t) {
+static status_t compute_status(double now, double link_t, double fc_t,
+                                int has_link, uint8_t up_lq) {
     if (link_t == 0 || (now - link_t) > LINK_STALE_S)
         return STATUS_NO_SIGNAL;
+    if (has_link && up_lq == 0)
+        return STATUS_NO_LINK;
     if (fc_t > 0 && (now - fc_t) > FC_STALE_S)
         return STATUS_STALE;
     return STATUS_LIVE;
@@ -152,6 +155,7 @@ typedef struct {
     /* Counts */
     int rx_frames;
     int unknown;
+    uint32_t type_counts[256]; /* indexed by raw CRSF frame type byte */
 } dashboard_t;
 
 static void dashboard_init(dashboard_t* d) {
@@ -167,7 +171,7 @@ static void dashboard_update(dashboard_t* d, cel_telemetry const* telem,
             d->up_rssi1 = telem->data.link.uplink_rssi1;
             d->up_rssi2 = telem->data.link.uplink_rssi2;
             d->up_lq = telem->data.link.uplink_quality;
-            d->up_snr = telem->data.link.uplink_snr - 128;
+            d->up_snr = telem->data.link.uplink_snr;
             d->power_idx = telem->data.link.uplink_power;
             d->rf_mode = telem->data.link.rf_mode;
             d->link_t = now;
@@ -227,6 +231,34 @@ static void rssi_color(double dbm) {
     else ansi_red();
 }
 
+/* Raw CRSF frame type byte -> name, for diagnostics.
+   Returns NULL for types not in cel_crsf_type. */
+static char const* crsf_type_name(uint8_t type) {
+    switch (type) {
+        case CEL_CRSF_TYPE_GPS:                return "GPS";
+        case CEL_CRSF_TYPE_VARIO:               return "VARIO";
+        case CEL_CRSF_TYPE_BATTERY:             return "BATTERY";
+        case CEL_CRSF_TYPE_BARO_ALT:            return "BARO_ALT";
+        case CEL_CRSF_TYPE_AIRSPEED:            return "AIRSPEED";
+        case CEL_CRSF_TYPE_HEARTBEAT:           return "HEARTBEAT";
+        case CEL_CRSF_TYPE_RPM:                 return "RPM";
+        case CEL_CRSF_TYPE_TEMP:                return "TEMP";
+        case CEL_CRSF_TYPE_VOLTAGES:            return "VOLTAGES";
+        case CEL_CRSF_TYPE_ESC_SENSOR:          return "ESC_SENSOR";
+        case CEL_CRSF_TYPE_LINK_STATS:          return "LINK_STATS";
+        case CEL_CRSF_TYPE_RC_CHANNELS:         return "RC_CHANNELS";
+        case CEL_CRSF_TYPE_ATTITUDE:            return "ATTITUDE";
+        case CEL_CRSF_TYPE_FLIGHT_MODE:         return "FLIGHT_MODE";
+        case CEL_CRSF_TYPE_DEVICE_PING:         return "DEVICE_PING";
+        case CEL_CRSF_TYPE_DEVICE_INFO:         return "DEVICE_INFO";
+        case CEL_CRSF_TYPE_PARAM_ENTRY:         return "PARAM_ENTRY";
+        case CEL_CRSF_TYPE_PARAM_READ:          return "PARAM_READ";
+        case CEL_CRSF_TYPE_PARAM_WRITE:         return "PARAM_WRITE";
+        case CEL_CRSF_TYPE_ELRS_STATUS:         return "ELRS_STATUS";
+        default:                                return NULL;
+    }
+}
+
 /* --------------------------------------------------------------------------- */
 /* Dashboard render - tracks line count for in-place redraw                    */
 /* --------------------------------------------------------------------------- */
@@ -235,7 +267,8 @@ static void render_dashboard(dashboard_t const* d,
                               char const* port, int baud,
                               double elapsed, int* lines) {
     double now = (double)time(NULL);
-    status_t status = compute_status(now, d->link_t, d->fc_t);
+    status_t status = compute_status(now, d->link_t, d->fc_t,
+                                      d->has_link, d->up_lq);
 
     /* Return to top of dashboard if already drawn */
     if (*lines > 0) {
@@ -326,6 +359,36 @@ static void render_dashboard(dashboard_t const* d,
     printf("\n");
     n++;
 
+    /* Frame type breakdown (top 6 by count) */
+    ansi_clear_line();
+    ansi_dim();
+    printf("  types:");
+    uint8_t used[256] = {0};
+    int shown = 0;
+    for (int k = 0; k < 6; k++) {
+        int best = -1;
+        uint32_t best_count = 0;
+        for (int t = 0; t < 256; t++) {
+            if (!used[t] && d->type_counts[t] > best_count) {
+                best_count = d->type_counts[t];
+                best = t;
+            }
+        }
+        if (best < 0) break;
+        used[best] = 1;
+        char const* name = crsf_type_name((uint8_t)best);
+        if (name != NULL) {
+            printf("  %s=%u", name, best_count);
+        } else {
+            printf("  0x%02X=%u", best, best_count);
+        }
+        shown++;
+    }
+    if (shown == 0) printf(" -");
+    ansi_reset();
+    printf("\n");
+    n++;
+
     *lines = n;
     fflush(stdout);
 }
@@ -361,11 +424,13 @@ static int list_ports(void) {
 
 /* Send a ping and wait for DEVICE_INFO to verify the module responds. */
 static int verify_connection(cel_serial_port* port) {
-    if (cel_crsf_param_ping(port, 2.0f) != 0) {
+    /* The module may take a few seconds to respond to the first ping,
-        cel_log_warn("No DEVICE_INFO response - module may not be connected");
+     * so retry a few times before giving up. */
-        return -1;
+    for (int attempt = 0; attempt < 3; attempt++) {
+        if (cel_crsf_param_ping(port, 2.0f) == 0) return 0;
     }
-    return 0;
+    cel_log_warn("No DEVICE_INFO response - module may not be connected");
+    return -1;
 }
 
 int main(int argc, char const* argv[]) {
@@ -453,6 +518,7 @@ int main(int argc, char const* argv[]) {
 
             double now = (double)time(NULL);
             for (int i = 0; i < n; i++) {
+                dash.type_counts[frames[i].type]++;
                 cel_telemetry telem;
                 if (cel_crsf_telemetry_parse(&frames[i], &telem) == 0) {
                     dashboard_update(&dash, &telem, now);
@@ -469,6 +535,14 @@ int main(int argc, char const* argv[]) {
             cel_serial_write(port, rc_buf, rc_len);
         }
 
+        /* Send DEVICE_PING every 5s so DEVICE_INFO replies keep showing up
+         * in the dashboard's type_counts, like the Python ping_loop. */
+        if (rc_count % 250 == 0) {
+            uint8_t ping_buf[8];
+            size_t ping_len = cel_crsf_build_ping_frame(ping_buf);
+            cel_serial_write(port, ping_buf, ping_len);
+        }
+
         /* Redraw dashboard every 100 ms */
         if (rc_count % 5 == 0) {
             double elapsed = difftime(time(NULL), t_start);