Add constant option for A1 FrSky SPI (retry)

When using external XJT it annoyingly beeps when A1 drops below 3.7v (72 out of 255). I removed frsky_spi_use_external_adc and added frsky_spi_a1_source = VBAT, EXTADC, CONST. To prevent XJT from beeping ever set CONST and XJT will assume that the "reciever" is powered with 5v. I messed up previous PR #7305 branch so I decided that it's easier to open a new one.

Closes #7297

src/main/interface/settings.c

@@ -311,6 +311,12 @@ static const char * const lookupTableMax7456Clock[] = {
 };
 #endif
 
+#ifdef USE_RX_FRSKY_SPI
+static const char * const lookupTableFrskySpiA1Source[] = {
+    "VBAT", "EXTADC", "CONST"
+};
+#endif
+
 #ifdef USE_GYRO_OVERFLOW_CHECK
 static const char * const lookupTableGyroOverflowCheck[] = {
     "OFF", "YAW", "ALL"
@@ -473,6 +479,9 @@ const lookupTableEntry_t lookupTables[] = {
 #ifdef USE_MAX7456
     LOOKUP_TABLE_ENTRY(lookupTableMax7456Clock),
 #endif
+#ifdef USE_RX_FRSKY_SPI
+    LOOKUP_TABLE_ENTRY(lookupTableFrskySpiA1Source),
+#endif
 #ifdef USE_RANGEFINDER
     LOOKUP_TABLE_ENTRY(lookupTableRangefinderHardware),
 #endif
@@ -1215,7 +1224,7 @@ const clivalue_t valueTable[] = {
     { "frsky_spi_offset",               VAR_INT8    | MASTER_VALUE, .config.minmax = { -127, 127 }, PG_RX_FRSKY_SPI_CONFIG, offsetof(rxFrSkySpiConfig_t, bindOffset) },
     { "frsky_spi_bind_hop_data",        VAR_UINT8   | MASTER_VALUE | MODE_ARRAY, .config.array.length = 50, PG_RX_FRSKY_SPI_CONFIG, offsetof(rxFrSkySpiConfig_t, bindHopData) },
     { "frsky_x_rx_num",                 VAR_UINT8   | MASTER_VALUE, .config.minmax = { 0, 255 }, PG_RX_FRSKY_SPI_CONFIG, offsetof(rxFrSkySpiConfig_t, rxNum) },
-    { "frsky_spi_use_external_adc",     VAR_UINT8   | MASTER_VALUE | MODE_LOOKUP, .config.lookup = { TABLE_OFF_ON }, PG_RX_FRSKY_SPI_CONFIG, offsetof(rxFrSkySpiConfig_t, useExternalAdc) },
+    { "frsky_spi_a1_source",            VAR_UINT8   | MASTER_VALUE | MODE_LOOKUP, .config.lookup = { TABLE_RX_FRSKY_SPI_A1_SOURCE }, PG_RX_FRSKY_SPI_CONFIG, offsetof(rxFrSkySpiConfig_t, a1Source) },
 #endif
     { "led_inversion",                  VAR_UINT8  | MASTER_VALUE, .config.minmax = { 0, ((1 << STATUS_LED_NUMBER) - 1) }, PG_STATUS_LED_CONFIG, offsetof(statusLedConfig_t, inversion) },
 #ifdef USE_DASHBOARD

src/main/interface/settings.h

@@ -79,6 +79,9 @@ typedef enum {
 #ifdef USE_MAX7456
     TABLE_MAX7456_CLOCK,
 #endif
+#ifdef USE_RX_FRSKY_SPI
+    TABLE_RX_FRSKY_SPI_A1_SOURCE,
+#endif
 #ifdef USE_RANGEFINDER
     TABLE_RANGEFINDER_HARDWARE,
 #endif

src/main/rx/cc2500_frsky_common.h

@@ -24,13 +24,19 @@
 
 #include "rx/rx_spi.h"
 
+typedef enum {
+  FRSKY_SPI_A1_SOURCE_VBAT = 0,
+  FRSKY_SPI_A1_SOURCE_EXTADC,
+  FRSKY_SPI_A1_SOURCE_CONST
+} frSkySpiA1Source_e;
+
 typedef struct rxFrSkySpiConfig_s {
     uint8_t autoBind;
     uint8_t bindTxId[2];
     int8_t  bindOffset;
     uint8_t bindHopData[50];
     uint8_t rxNum;
-    uint8_t useExternalAdc;
+    uint8_t a1Source;
 } rxFrSkySpiConfig_t;
 
 PG_DECLARE(rxFrSkySpiConfig_t, rxFrSkySpiConfig);

src/main/rx/cc2500_frsky_d.c

@@ -66,6 +66,8 @@ static bool telemetryEnabled = false;
 
 #define MAX_SERIAL_BYTES 64
 
+#define A1_CONST_D 100
+
 static uint8_t telemetryBytesGenerated;
 static uint8_t serialBuffer[MAX_SERIAL_BYTES]; // buffer for telemetry serial data
 
@@ -113,10 +115,16 @@ static void frSkyDTelemetryWriteByte(const char data)
 static void buildTelemetryFrame(uint8_t *packet)
 {
     uint8_t a1Value;
-    if (rxFrSkySpiConfig()->useExternalAdc) {
+    switch (rxFrSkySpiConfig()->a1Source) {
-        a1Value = (adcGetChannel(ADC_EXTERNAL1) & 0xff0) >> 4;
+    case FRSKY_SPI_A1_SOURCE_VBAT:
-    } else {
         a1Value = (getBatteryVoltage() / 5) & 0xff;
+        break;
+    case FRSKY_SPI_A1_SOURCE_EXTADC:
+        a1Value = (adcGetChannel(ADC_EXTERNAL1) & 0xff0) >> 4;
+        break;
+    case FRSKY_SPI_A1_SOURCE_CONST:
+        a1Value = A1_CONST_D & 0xff;
+        break;
     }
     const uint8_t a2Value = (adcGetChannel(ADC_RSSI)) >> 4;
     telemetryId = packet[4];

src/main/rx/cc2500_frsky_shared.c

@@ -79,7 +79,7 @@ PG_RESET_TEMPLATE(rxFrSkySpiConfig_t, rxFrSkySpiConfig,
         0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
         0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
     .rxNum = 0,
-    .useExternalAdc = false,
+    .a1Source = FRSKY_SPI_A1_SOURCE_VBAT,
 );
 
 static void initialise() {

src/main/rx/cc2500_frsky_x.c

@@ -97,6 +97,8 @@ const uint16_t crcTable[] = {
 
 #define TELEMETRY_SEQUENCE_LENGTH 4
 
+#define A1_CONST_X 50
+
 typedef struct telemetrySequenceMarkerData_s {
     unsigned int packetSequenceId: 2;
     unsigned int unused: 1;
@@ -197,10 +199,16 @@ static void buildTelemetryFrame(uint8_t *packet)
         frame[4] = (uint8_t)cc2500getRssiDbm() | 0x80;
     } else {
         uint8_t a1Value;
-        if (rxFrSkySpiConfig()->useExternalAdc) {
+        switch (rxFrSkySpiConfig()->a1Source) {
-            a1Value = (uint8_t)((adcGetChannel(ADC_EXTERNAL1) & 0xfe0) >> 5);
+        case FRSKY_SPI_A1_SOURCE_VBAT:
-        } else {
             a1Value = getLegacyBatteryVoltage() & 0x7f;
+            break;
+        case FRSKY_SPI_A1_SOURCE_EXTADC:
+            a1Value = (uint8_t)((adcGetChannel(ADC_EXTERNAL1) & 0xfe0) >> 5);
+            break;
+        case FRSKY_SPI_A1_SOURCE_CONST:
+            a1Value = A1_CONST_X & 0x7f;
+            break;
         }
         frame[4] = a1Value;
     }