Radio controller not working

[asGenn]

Hello,
I'm using the FlySky i6 transmitter with the FS-iA6B receiver. This receiver supports either iBUS or PPM signal output. Since your code doesn't include support for iBUS, I decided to use PPM instead. However, I'm encountering a problem:

When I connect the receiver's RX (PPM output) pin to any GPIO pin on my ESP32 Devkit v1 board, I don't receive any signal. For example, when I try to run prcl or calradio, I get the following error:

==== Radio Calibration ====
ERROR: radio not connected. Connect and try again

==== Radio Calibration Aborted ====

I have already enabled the PPM output setting from the transmitter, so that should be correct.

My question is: Am I wiring something incorrectly, or is there a different approach I need to take to get the ESP32 to read PPM signals properly from the FS-iA6B receiver?

[qqqlab]

Hi @asGenn , thanks for trying madflight.

Did you set the following in madflight_config?

rcl_gizmo PPM
pin_rcl_ppm <your ppm pin>

If yes: are you absolutely sure your receiver is outputting PPM?

[asGenn]

Hi again @qqqlab ,
I enabled PPM output on my FlySky i6 transmitter .

However, I'm not entirely sure if the receiver is actually outputting PPM correctly. On the transmitter, I’ve activated PPM mode under “RX Setup > Output Mode,” and I connected the signal wire from channel 1 (CH1) of the FS-iA6B (which is the correct PPM output port) to one of the ESP32's GPIO pins.

the configuration file:

/*========================================================================================================================
                                              MADFLIGHT CONFIG
==========================================================================================================================

The configuration is loaded from two strings: first from madflight_board in <madflight_board.h>, and then from 
madflight_config in this file. If the same setting occurs more than once, the last one is applied.

The strings are multi-line raw strings in with a key-value list. Anything after '#' or '/' is ignored as comment.

You have 3 options to setup the flight controller:

  1) Default - Keep "#include <madflight_board.h>", this defines the default pinout as shown on https://madflight.com 
     for the supported processor families. Now edit madflight_config below, and uncomment and configure imu_gizmo, 
     imu_bus_type, rcl_gizmo, and other lines as needed. (Do not change the pin_xxx_yyy and xxx_yyy_bus settings.)
 
  2) BetaFlight - Change "#include <madflight_board.h>" to the BetaFlight flight controller you want to use, for example: 
     "#include <madflight_zzz_MTKS-MATEKH743.h>". See library/madflight/src for all available boards. Edit madflight_config
     to fine-tune the configuration.
 
  4) Bare Metal - Remove "#include <madflight_board.h>", and set the full configuration in madflight_config below.

Pins and spi/i2c/serial busses use zero-based numbering, i.e. "gps_ser_bus 0" connects the GPS to the first serial bus
with pins pin_ser0_tx and pin_ser0_rx. Pins use GPIO numbers, not physical pin numbers. Use -1 to disable a pin or bus.

You can also modify the configuration from the CLI, for example "set imu_gizmo MPU6500" or "set imu_spi_bus 1", then
use "cwrite" to save the config to eeprom and reboot to use the new config.

If things do not work as expected, have a good look at the startup messages!

========================================================================================================================*/

#include <madflight_board.h>

const char madflight_config[] = R""(

//--- IMU --- Inertial Measurement Unit  (use spi -OR- i2c bus)
//imu_gizmo      MPU6050    // options: NONE, BMI270, MPU6000, MPU6050, MPU6500, MPU9150, MPU9250, ICM45686, ICM42688
//imu_bus_type   I2C     // options: SPI, I2C (not all combinations of gizmo and bus_type are supported)
//imu_align      CW0     // options: CW0, CW90, CW180, CW270, CW0FLIP, CW90FLIP, CW180FLIP, CW270FLIP
//imu_spi_bus    -1 //spi
//pin_imu_cs     -1 //spi
//pin_imu_int    19 //spi and i2c
//imu_i2c_bus    0 //i2c
//imu_i2c_adr     104 //i2c: enter decimal i2c address, not hex (use 0 for default i2c address)

// IMPORTANT: the IMU sensor should be the ONLY sensor on the selected bus


//--- RCL --- Remote Controller Link  (use serial bus -OR- ppm pin)
rcl_gizmo      PPM  // options: NONE, MAVLINK, CRSF, SBUS, DSM, PPM
rcl_num_ch     6     // number of channels
rcl_deadband   20     // center stick deadband
//rcl_ser_bus   -1
pin_rcl_ppm   27

//--- BAR --- Barometer
//bar_gizmo      NONE  // options: NONE, BMP390, BMP388, BMP280, MS5611, HP203B
//bar_i2c_adr    0
//bar_i2c_bus   -1

//--- MAG --- Magnetometer
//mag_gizmo      NONE  // options: NONE, QMC5883, QMC6309, RM3100
//mag_i2c_adr    0
//mag_i2c_bus   -1

//--- BAT --- Battery Monitor  (use i2c bus -OR- adc pins)
//bat_gizmo      NONE  // options: NONE, ADC, INA226, INA228
//bat_i2c_adr    0
//bat_i2c_bus   -1
//pin_bat_i     -1
//pin_bat_v     -1

//--- GPS ---
//gps_gizmo      NONE  // options: NONE, UBLOX
//gps_baud       0   // use 0 for auto baud
//gps_ser_bus   -1

//--- BBX --- Black Box Data Logger  (use spi -OR- mmc)
//bbx_gizmo      NONE  // options: NONE, SDSPI, SDMMC
//pin_bbx_cs    -1  // spi
//bbx_spi_bus   -1  // spi
//pin_mmc_dat   -1  // mmc
//pin_mmc_clk   -1  // mmc
//pin_mmc_cmd   -1  // mmc

//--- RDR --- Radar (use serial bus -OR- trig+echo pins)
//rdr_gizmo      NONE  // options: NONE, LD2411S, LD2413, USD1, SR04
//rdr_baud       0
//rdr_ser_bus   -1
//pin_rdr_trig  -1
//pin_rdr_echo  -1

//--- LED ---
//led_on         LOW_IS_ON // options: LOW_IS_ON, HIGH_IS_ON
//pin_led       -1

//--- AHR --- AHRS (keep MAHONY, unless you want to experiment)
//ahr_gizmo      MAHONY  // options: MAHONY, MAHONY_BF, MADGWICK, VQF

//--- Serial bus 0 ---
//pin_ser0_rx   16
//pin_ser0_tx   17

//--- Serial bus 1 ---
//pin_ser1_rx   -1
//pin_ser1_tx   -1 

//--- SPI bus 0 ---
//pin_spi0_miso -1
//pin_spi0_mosi -1
//pin_spi0_sclk -1

//--- SPI bus 1 ---
//pin_spi1_miso -1
//pin_spi1_mosi -1
//pin_spi1_sclk -1

//--- I2C Bus 0 ---
//pin_i2c0_sda  21
//pin_i2c0_scl  22

//--- I2C Bus 1 ---
//pin_i2c1_sda  -1
//pin_i2c1_scl  -1

//--- OUT Pins ---
//pin_out0      -1
//pin_out1      -1
//pin_out2      -1
//pin_out3      -1
//pin_out4      -1
//pin_out5      -1
//pin_out6      -1
//pin_out7      -1
//pin_out8      -1
//pin_out9      -1
//pin_out10     -1
//pin_out11     -1
//pin_out12     -1
//pin_out13     -1
//pin_out14     -1
//pin_out15     -1

)""; // End of madflight_config


//========================================================================================================================//
//                                               COMPILER OPTIONS                                                         //
//========================================================================================================================//

// Reset config eeprom to defaults (uncomment this, upload, execute, then comment out, and upload again)
//#define MF_CONFIG_CLEAR

// Uncomment to print additional debug information and reduce startup delay
//#define MF_DEBUG

I'm not sure which GPIO pin on the ESP32 I should use here. Does the ESP32 have a specific pin for receiving PPM input? Or can I use any digital GPIO input (like GPIO 4 or 15)? Also, is there any way to confirm that the PPM signal is actually being transmitted from the receiver?

I would appreciate it if you could clarify how to properly wire and configure PPM input with an ESP32. Thanks!

[qqqlab]

As this appears to me an issue with your setup and not with madflight, I'm moving this to the Discussion section.

On the ESP32 you can use almost any pin for PPM input. Please use an oscilloscope, digital analyzer, or a small ESP32 program to check that your receiver is outputting a valid PPM signal. You'll find enough resources online on both ESP32 and PPM.

[tiberiucorbu]

I only have ERLS on my hand and no matter what I have tried : MAVLINK, SBUS, CRSF none of them seem to work, not sure if is an issue or a configuration problem. Tried 3 diffrent recievers but none worked.

When activating CRSF after startup -> Core 1 panics :

22:24:31.822 -> RCL: CRSF - thr_ch:1 thr_pull:1100 thr_mid:1500 thr_push:1900 rol_ch:2 rol_left:1100 rol_mid:1500 rol_right:1900 pit_ch:3 pit_pull:1100 pit_mid:1500 pit_push:1900 yaw_ch:4 yaw_left:1100 yaw_mid:1500 yaw_right:1900 arm_ch:5 arm_min:1600 arm_max:2500 flt_ch:6 flt_min:1165 flt_max:1815 ser_bus:1 baud:-1 num_ch:16 deadband:0 
22:24:31.855 -> Guru Meditation Error: Core  1 panic'ed (StoreProhibited). Exception was unhandled.
22:24:31.855 -> 
22:24:31.855 -> Core  1 register dump:
22:24:31.855 -> PC      : 0x42015ce9  PS      : 0x00060430  A0      : 0x82004d2e  A1      : 0x3fca3360  
22:24:31.886 -> A2      : 0x3fc98470  A3      : 0x3fc98484  A4      : 0xffffffff  A5      : 0x3fc9fa64  
22:24:31.886 -> A6      : 0x3fca4a1c  A7      : 0x3fc9774c  A8      : 0x00000010  A9      : 0xb61626e3  
22:24:31.886 -> A10     : 0x000005dc  A11     : 0x0001c200  A12     : 0x0800001c  A13     : 0x00000015  
22:24:31.886 -> A14     : 0x3fc97370  A15     : 0x00000064  SAR     : 0x0000000a  EXCCAUSE: 0x0000001d  
22:24:31.886 -> EXCVADDR: 0xb61626e3  LBEG    : 0x42015ce9  LEND    : 0x42015cee  LCOUNT  : 0x0000000f  
22:24:31.918 -> 
22:24:31.918 -> 
22:24:31.918 -> Backtrace: 0x42015ce6:0x3fca3360 0x42004d2b:0x3fca3390 0x42005023:0x3fca3410 0x4201e0fa:0x3fca3430 0x4037bf9e:0x3fca3450
22:24:31.918 -> 
22:24:31.918 -> 
22:24:31.918 -> 
22:24:31.918 -> 
22:24:31.918 -> ELF file SHA256: 70e661422
22:24:31.918 -> 
22:24:32.047 -> Rebooting...

The other two modes show no data on ppwm or pall

my configuration as follows :

/*========================================================================================================================
                                              MADFLIGHT CONFIG
==========================================================================================================================

The configuration is loaded from two strings: first from madflight_board in <madflight_board.h>, and then from 
madflight_config in this file. If the same setting occurs more than once, the last one is applied.

The strings are multi-line raw strings in with a key-value list. Anything after '#' or '/' is ignored as comment.

You have 3 options to setup the flight controller:

  1) Default - Keep "#include <madflight_board.h>", this defines the default pinout as shown on https://madflight.com 
     for the supported processor families. Now edit madflight_config below, and uncomment and configure imu_gizmo, 
     imu_bus_type, rcl_gizmo, and other lines as needed. (Do not change the pin_xxx_yyy and xxx_yyy_bus settings.)
 
  2) BetaFlight - Change "#include <madflight_board.h>" to the BetaFlight flight controller you want to use, for example: 
     "#include <madflight_zzz_MTKS-MATEKH743.h>". See library/madflight/src for all available boards. Edit madflight_config
     to fine-tune the configuration.
 
  3) Bare Metal - Remove "#include <madflight_board.h>", and set the full configuration in madflight_config below.

Pins and spi/i2c/serial busses use zero-based numbering, i.e. "gps_ser_bus 0" connects the GPS to the first serial bus
with pins pin_ser0_tx and pin_ser0_rx. Pins use GPIO numbers, not physical pin numbers. Use -1 to disable a pin or bus.

You can also modify the configuration from the CLI, for example "set imu_gizmo MPU6500" or "set imu_spi_bus 1", then
use "save" to save the config to eeprom and reboot to use the new config.

If things do not work as expected, have a good look at the startup messages!

========================================================================================================================*/

// #include <madflight_board.h>

const char madflight_config[] = R""(

//--- IMU --- Inertial Measurement Unit  (use spi -OR- i2c bus)
imu_gizmo      MPU6500    // options: NONE, BMI270, MPU6000, MPU6050, MPU6500, MPU9150, MPU9250, ICM45686, ICM42688
imu_bus_type   SPI     // options: SPI, I2C (not all combinations of gizmo and bus_type are supported)
//imu_align      CW0     // options: CW0, CW90, CW180, CW270, CW0FLIP, CW90FLIP, CW180FLIP, CW270FLIP
imu_spi_bus    0 //spi
pin_imu_cs     10 //spi
pin_imu_int    14 //spi and i2c
//imu_i2c_bus    -1 //i2c
//imu_i2c_adr     0 //i2c: enter decimal i2c address, not hex (use 0 for default i2c address)

// IMPORTANT: the IMU sensor should be the ONLY sensor on the selected bus


//--- RCL --- Remote Controller Link  (use serial bus -OR- ppm pin)
rcl_gizmo      CRSF  // options: NONE, MAVLINK, CRSF, SBUS, DSM, PPM
rcl_num_ch     16     // number of channels
rcl_deadband   0     // center stick deadband
rcl_baud       -1
rcl_ser_bus   1
pin_rcl_ppm   -1

//--- BAR --- Barometer
bar_gizmo      NONE // options: NONE, BMP390, BMP388, BMP280, MS5611, HP203B
bar_i2c_adr    0
bar_i2c_bus   -1

//--- MAG --- Magnetometer
mag_gizmo      NONE  // options: NONE, QMC5883, QMC6309, RM3100
mag_i2c_adr    0
mag_i2c_bus   -1

//--- BAT --- Battery Monitor  (use i2c bus -OR- adc pins)
bat_gizmo      NONE  // options: NONE, ADC, INA226, INA228
bat_i2c_adr    0
bat_i2c_bus   -1
pin_bat_i     -1
pin_bat_v     -1
bat_cal_v      1 //adc voltage scale, value is: actual_voltage_in_v / adc_reading
bat_cal_i,     1 //adc current scale, value is: actual_current_in_a / adc_reading; for ina226/228: rshunt value in ohm

//--- GPS ---
gps_gizmo      UBLOX  // options: NONE, UBLOX
gps_baud     9600    // use 0 for auto baud
gps_ser_bus    0

//--- BBX --- Black Box Data Logger  (use spi -OR- mmc)
bbx_gizmo      NONE  // options: NONE, SDSPI, SDMMC
pin_bbx_cs    -1  // spi
bbx_spi_bus   -1  // spi
pin_mmc_dat   -1  // mmc
pin_mmc_clk   -1  // mmc
pin_mmc_cmd   -1  // mmc

//--- RDR --- Radar (use serial bus -OR- trig+echo pins)
rdr_gizmo      NONE  // options: NONE, LD2411S, LD2413, USD1, SR04
rdr_baud       -1
rdr_ser_bus   -1
pin_rdr_trig  -1
pin_rdr_echo  -1

//--- LED ---
led_on         LOW_IS_ON // options: LOW_IS_ON, HIGH_IS_ON
pin_led       2

//--- AHR --- AHRS (keep MAHONY, unless you want to experiment)
ahr_gizmo      MAHONY  // options: MAHONY, MAHONY_BF, MADGWICK, VQF

//--- Serial bus 0 ---
pin_ser0_rx   8
pin_ser0_tx   3

//--- Serial bus 1 ---
pin_ser1_rx   20
pin_ser1_tx   21 

//--- SPI bus 0 ---
pin_spi0_miso 12
pin_spi0_mosi 11
pin_spi0_sclk 13

//--- SPI bus 1 ---
pin_spi1_miso -1
pin_spi1_mosi -1
pin_spi1_sclk -1

//--- I2C Bus 0 ---
pin_i2c0_sda  -1
pin_i2c0_scl  -1

//--- I2C Bus 1 ---
pin_i2c1_sda  -1
pin_i2c1_scl  -1

//--- OUT Pins ---
pin_out0      -1
pin_out2      -1
pin_out1      -1
pin_out3      -1
pin_out4      -1
pin_out5      -1
pin_out6      -1
pin_out7      -1
pin_out8      -1
pin_out9      -1
pin_out10     -1
pin_out11     -1
pin_out12     -1
pin_out13     -1
pin_out14     -1
pin_out15     -1

)""; // End of madflight_config


//========================================================================================================================//
//                                               COMPILER OPTIONS                                                         //
//========================================================================================================================//

// Reset config eeprom to defaults (uncomment this, upload, execute, then comment out, and upload again)
//#define MF_CONFIG_CLEAR

// Uncomment to print additional debug information and reduce startup delay
#define MF_DEBUG

[Stillalive222]

were you able to get ppm or ibus working with that fsi6? i am facing the same problem for days and even tried modifying the source files but with no luck.

[asGenn]

Same thing for me too, I couldn't connect the receiver somehow. As a last resort, I will check the receiver's outputs in the lab to see if they are coming in ppm, but unfortunately I haven't had the chance yet.

[Stillalive222]

i checked with two receivers and ppm is working fine on same hardware and pin but i thing it has to do something with this code addressing for longer 5000us pulses while these deal with 3ms and only for rising edges.
you can test it yourself from this sample gpt gave me :

#define PPM_PIN 13
#define MAX_CHANNELS 8

volatile uint32_t lastMicros = 0;
volatile uint16_t ppmValues[MAX_CHANNELS];
volatile uint8_t channelIndex = 0;
volatile bool newFrame = false;

void IRAM_ATTR ppmISR() {
  uint32_t now = micros();
  uint32_t duration = now - lastMicros;
  lastMicros = now;

  if (duration > 3000) {
    // Long gap = sync pulse → start new frame
    channelIndex = 0;
  } else if (channelIndex < MAX_CHANNELS) {
    ppmValues[channelIndex] = duration;
    channelIndex++;
    if (channelIndex == MAX_CHANNELS) {
      newFrame = true;
    }
  }
}

void setup() {
  Serial.begin(115200);
  delay(1000);
  Serial.println("PPM reader started on pin 13");

  pinMode(PPM_PIN, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(PPM_PIN), ppmISR, RISING);
}

void loop() {
  if (newFrame) {
    noInterrupts(); // Prevent updates while reading
    uint16_t values[MAX_CHANNELS];
    for (int i = 0; i < MAX_CHANNELS; i++) {
      values[i] = ppmValues[i];
    }
    newFrame = false;
    interrupts();

    Serial.print("PPM: ");
    for (int i = 0; i < MAX_CHANNELS; i++) {
      Serial.print(values[i]);
      Serial.print(" ");
    }
    Serial.println("us");
  }
}

[asGenn]

can we apply this to source code ?

[Stillalive222]

this is just a test code to see if the esp32 is actually reading any ppm signals but you can surely apply the same methods to make changes in the source file. Make sure you edit them in the library location itself. I tried editing the source files but got nothing , see if you could give it a try too.

[tiberiucorbu]

I have debuged it a bit and found out the problem with CRFS, is because the PWM pointer is smaller than 16 , Implemented a fix into my fork here : b6e610b#diff-5eeb1cafd73c92c318be78f7fdf15bde1d3048d1f2008b319431efd20ddd793bR60-R61 also got it running with the latest idf 6.11.0 in the same branch

To test I used my tool of choise platfomio in a diffrent repo https://github.com/tiberiucorbu/madflight-platformio-custom/tree/main

[asGenn]

Does this work on receivers that give ppm output?

[tiberiucorbu]

I'm not sure , I don't have a ready made PPM receiver, but looking at the code for PPM it doesn't pushes the read values to this PWM pointer like in CRFS implementation

void __ISR_getPPM() {
  static uint32_t ppm_counter = 0;
  static uint32_t tpulse_last = 0;
  uint32_t tpulse = micros();
  uint32_t dt_ppm = tpulse - tpulse_last;
  tpulse_last = tpulse;

  if (dt_ppm > 5000) { //Waiting for long pulse to indicate a new pulse train has arrived
    ppm_counter = 0;
  }

  if (ppm_counter >= 1 && ppm_counter <= 6) { //First-Sixth pulse
    __ISR_channel[ppm_counter-1] = dt_ppm;
  }

  if (ppm_counter == 6) { //Sixth pulse
    __ISR_rcl_updated = true;
  }
  
  ppm_counter = ppm_counter + 1;
}

it should have at the end of the frame from ppm an assingment to the this.pwm[i] pointer but I don't see any.

[asGenn]

I see then the code seems wrong.

[vidma]

interesting, likely I'm seeing something related (a freeze?) just after radio callibration over CRSF (ELRS). Before calibration it works, just I have weird channel mapping.

calibration seem to finish, this is the last msg:
RCL: CRSF - thr_ch:3 thr_pull:989 thr_mid:1511 thr_push:2012 rol_ch:1 rol_left:989 rol_mid:1502 rol_right:2010 pit_ch:2 pit_pull:2008 pit_mid:1495 pit_push:991 yaw_ch:4 yaw_left:1109 yaw_mid:1617 yaw_right:2012 arm_ch:5 arm_min:1499 arm_max:2500 flt_ch:7 flt_min:999 flt_max:2000 ser_bus:0 baud:0 num_ch:8 deadband:0

the callibration process itself is pretty nice though!

[vidma]

calibration for mavlink works however! 👏 . Using main branch from madflight (will check for telemetry, but telem seem missing in this case) - ELRS has option to use mavlink between RC and FC.