Issue with SBUS Signal Transmission on ESP32-CAM Using SoftSerial

moh43 · May 25, 2024, 7:08pm

Hi all,I'm using the ESP32-CAM to recognize QR codes, and everything was working perfectly until I started using SoftSerial to transmit the SBUS signal. I can receive the SBUS signal via RX2, but for my project, I need to send the SBUS signal to the flight controller.

However, I received an error message:
E (2304) gpio: gpio_install_isr_service(449): GPIO isr service already installed
Here is the code :

#include "esp_camera.h"
#include "SBUS.h"
#include <SoftwareSerial.h>

#define RX_PIN 13  // RX
#define TX_PIN 15  // TX

SoftwareSerial mySerial(RX_PIN, TX_PIN);

SBUS x8r(Serial2);

uint16_t mohamed[16];
bool failSafe;
bool lostFrame;

#define PWDN_GPIO_NUM     32
#define RESET_GPIO_NUM    -1
#define XCLK_GPIO_NUM      0
#define SIOD_GPIO_NUM     26
#define SIOC_GPIO_NUM     27
#define Y9_GPIO_NUM       35
#define Y8_GPIO_NUM       34
#define Y7_GPIO_NUM       39
#define Y6_GPIO_NUM       36
#define Y5_GPIO_NUM       21
#define Y4_GPIO_NUM       19
#define Y3_GPIO_NUM       18
#define Y2_GPIO_NUM        5
#define VSYNC_GPIO_NUM    25
#define HREF_GPIO_NUM     23
#define PCLK_GPIO_NUM     22

// Function to configure and initialize the camera
static void configCamera() {
    camera_config_t config;
    config.ledc_channel = LEDC_CHANNEL_0;
    config.ledc_timer = LEDC_TIMER_0;
    config.pin_d0 = Y2_GPIO_NUM;
    config.pin_d1 = Y3_GPIO_NUM;
    config.pin_d2 = Y4_GPIO_NUM;
    config.pin_d3 = Y5_GPIO_NUM;
    config.pin_d4 = Y6_GPIO_NUM;
    config.pin_d5 = Y7_GPIO_NUM;
    config.pin_d6 = Y8_GPIO_NUM;
    config.pin_d7 = Y9_GPIO_NUM;
    config.pin_xclk = XCLK_GPIO_NUM;
    config.pin_pclk = PCLK_GPIO_NUM;
    config.pin_vsync = VSYNC_GPIO_NUM;
    config.pin_href = HREF_GPIO_NUM;
    config.pin_sscb_sda = SIOD_GPIO_NUM;
    config.pin_sscb_scl = SIOC_GPIO_NUM;
    config.pin_pwdn = PWDN_GPIO_NUM;
    config.pin_reset = RESET_GPIO_NUM;
    config.xclk_freq_hz = 20000000;
    config.pixel_format = PIXFORMAT_JPEG;

    config.frame_size = FRAMESIZE_VGA;
    config.jpeg_quality = 12;
    config.fb_count = 1;

    esp_err_t err = esp_camera_init(&config);
    if (err != ESP_OK) {
        Serial.printf("Camera init failed with error 0x%x", err);
        return;
    }
}


void setup() {
  Serial.begin(115200);
  mySerial.begin(100000, SWSERIAL_8E2);
  x8r.begin(16, 17, true, 100000);

  configCamera();

}
void loop() 
}

srnet · May 25, 2024, 8:11pm

Why are you using software serial on an ESP32CAM when you can use hardware serial ?

moh43 · May 25, 2024, 8:25pm

I only have the RX pin (RGPIO16) available on my ESP32-CAM.

sterretje · May 26, 2024, 3:32am

I know hardly anything about ESP32 devices and I only know a little bit about the SBUS. But below strikes me as odd.

x8r is an SBUS device. Do you have a second SBUS device that requires the use of SoftwareSerial?

Note:
I doubt that your presented code will compile

srnet · May 26, 2024, 6:18am

Pin 16 is the select pin for the PSRAM, 17 is the PSRAM CLK.

Plus, software serial does allow you to allocate a serial interface to any free pins, but on an ESP32 you can do that with hardware serial too.

moh43 · May 26, 2024, 7:26am

I'm not using PSRAM, so I'm able to use Pin 16. I still need another serial, and based on your experience, I'll create a hardware serial. Could you please tell me which pins you have used before? I want to make sure, as I chose GPIO12 and GPIO13 for the ESP32-CAM.

srnet · May 26, 2024, 7:47am

You can use Serial2 like this;

Serial2.begin(9600, SERIAL_8N1, TXpin, RXpin);

I have used pin 33 for outputting debug info via Serial2.

moh43 · May 26, 2024, 9:49am

Thank you, it worked perfectly. However, when I used WiFi, it started rebooting

Guru Meditation Error: Core  1 panic'ed (LoadProhibited). Exception was unhandled.

Core  1 register dump:
PC      : 0x4008e5fc  PS      : 0x00060d30  A0      : 0x800d71c9  A1      : 0x3ffcb5d0  
A2      : 0xffffffff  A3      : 0xffffffff  A4      : 0xffffffff  A5      : 0x00060d23  
A6      : 0x00060d23  A7      : 0x00000001  A8      : 0x00000001  A9      : 0x00000004  
A10     : 0x00060d23  A11     : 0x3ffc4d88  A12     : 0x3ffc4a38  A13     : 0x00004e20  
A14     : 0x007bf528  A15     : 0x003fffff  SAR     : 0x00000017  EXCCAUSE: 0x0000001c  
EXCVADDR: 0x0000003f  LBEG    : 0x4008b699  LEND    : 0x4008b6a9  LCOUNT  : 0xfffffffc

here is the code:

#include <WiFi.h>
#include "esp_camera.h"
#include "SBUS.h"
#include <HardwareSerial.h>

HardwareSerial UART1(2);

#define TX_PIN 12
#define RX_PIN 16

#define num_channels 16

SBUS x8r(Serial2);
uint16_t mohamed[num_channels];
bool failSafe;
bool lostFrame;

const char* ssid = "Redmi Note 10S";
const char* password = "1234567899";

#define PWDN_GPIO_NUM     32
#define RESET_GPIO_NUM    -1
#define XCLK_GPIO_NUM      0
#define SIOD_GPIO_NUM     26
#define SIOC_GPIO_NUM     27
#define Y9_GPIO_NUM       35
#define Y8_GPIO_NUM       34
#define Y7_GPIO_NUM       39
#define Y6_GPIO_NUM       36
#define Y5_GPIO_NUM       21
#define Y4_GPIO_NUM       19
#define Y3_GPIO_NUM       18
#define Y2_GPIO_NUM        5
#define VSYNC_GPIO_NUM    25
#define HREF_GPIO_NUM     23
#define PCLK_GPIO_NUM     22

static void configCamera() {
    camera_config_t config;
    config.ledc_channel = LEDC_CHANNEL_0;
    config.ledc_timer = LEDC_TIMER_0;
    config.pin_d0 = Y2_GPIO_NUM;
    config.pin_d1 = Y3_GPIO_NUM;
    config.pin_d2 = Y4_GPIO_NUM;
    config.pin_d3 = Y5_GPIO_NUM;
    config.pin_d4 = Y6_GPIO_NUM;
    config.pin_d5 = Y7_GPIO_NUM;
    config.pin_d6 = Y8_GPIO_NUM;
    config.pin_d7 = Y9_GPIO_NUM;
    config.pin_xclk = XCLK_GPIO_NUM;
    config.pin_pclk = PCLK_GPIO_NUM;
    config.pin_vsync = VSYNC_GPIO_NUM;
    config.pin_href = HREF_GPIO_NUM;
    config.pin_sscb_sda = SIOD_GPIO_NUM;
    config.pin_sscb_scl = SIOC_GPIO_NUM;
    config.pin_pwdn = PWDN_GPIO_NUM;
    config.pin_reset = RESET_GPIO_NUM;
    config.xclk_freq_hz = 20000000;
    config.pixel_format = PIXFORMAT_JPEG;

    config.frame_size = FRAMESIZE_VGA;
    config.jpeg_quality = 12;
    config.fb_count = 1;

    esp_err_t err = esp_camera_init(&config);
    if (err != ESP_OK) {
        Serial.printf("Camera init failed with error 0x%x", err);
        return;
    }
}

#define SBUS_MIN_OFFSET 173
#define SBUS_MID_OFFSET 992
#define SBUS_MAX_OFFSET 1811

#define SBUS_CHANNEL_NUMBER 16
#define SBUS_PACKET_LENGTH 25
#define SBUS_FRAME_HEADER 0x0f
#define SBUS_FRAME_FOOTER 0x00
#define SBUS_FRAME_FOOTER_V2 0x04
#define SBUS_STATE_FAILSAFE 0x08
#define SBUS_STATE_SIGNALLOSS 0x04
#define SBUS_UPDATE_RATE 15 //ms

void sbusPreparePacket(uint8_t packet[], int channels[], bool isSignalLoss, bool isFailsafe){

    static int output[SBUS_CHANNEL_NUMBER] = {0};
    for (uint8_t i = 0; i < SBUS_CHANNEL_NUMBER; i++) {
        output[i] = channels[i];
    }

    uint8_t stateByte = 0x00;
    if (isSignalLoss) {
        stateByte |= SBUS_STATE_SIGNALLOSS;
    }
    if (isFailsafe) {
        stateByte |= SBUS_STATE_FAILSAFE;
    }
    packet[0] = SBUS_FRAME_HEADER; //Header

    packet[1] = (uint8_t) (output[0] & 0x07FF);
    packet[2] = (uint8_t) ((output[0] & 0x07FF)>>8 | (output[1] & 0x07FF)<<3);
    packet[3] = (uint8_t) ((output[1] & 0x07FF)>>5 | (output[2] & 0x07FF)<<6);
    packet[4] = (uint8_t) ((output[2] & 0x07FF)>>2);
    packet[5] = (uint8_t) ((output[2] & 0x07FF)>>10 | (output[3] & 0x07FF)<<1);
    packet[6] = (uint8_t) ((output[3] & 0x07FF)>>7 | (output[4] & 0x07FF)<<4);
    packet[7] = (uint8_t) ((output[4] & 0x07FF)>>4 | (output[5] & 0x07FF)<<7);
    packet[8] = (uint8_t) ((output[5] & 0x07FF)>>1);
    packet[9] = (uint8_t) ((output[5] & 0x07FF)>>9 | (output[6] & 0x07FF)<<2);
    packet[10] = (uint8_t) ((output[6] & 0x07FF)>>6 | (output[7] & 0x07FF)<<5);
    packet[11] = (uint8_t) ((output[7] & 0x07FF)>>3);
    packet[12] = (uint8_t) ((output[8] & 0x07FF));
    packet[13] = (uint8_t) ((output[8] & 0x07FF)>>8 | (output[9] & 0x07FF)<<3);
    packet[14] = (uint8_t) ((output[9] & 0x07FF)>>5 | (output[10] & 0x07FF)<<6);  
    packet[15] = (uint8_t) ((output[10] & 0x07FF)>>2);
    packet[16] = (uint8_t) ((output[10] & 0x07FF)>>10 | (output[11] & 0x07FF)<<1);
    packet[17] = (uint8_t) ((output[11] & 0x07FF)>>7 | (output[12] & 0x07FF)<<4);
    packet[18] = (uint8_t) ((output[12] & 0x07FF)>>4 | (output[13] & 0x07FF)<<7);
    packet[19] = (uint8_t) ((output[13] & 0x07FF)>>1);
    packet[20] = (uint8_t) ((output[13] & 0x07FF)>>9 | (output[14] & 0x07FF)<<2);
    packet[21] = (uint8_t) ((output[14] & 0x07FF)>>6 | (output[15] & 0x07FF)<<5);
    packet[22] = (uint8_t) ((output[15] & 0x07FF)>>3);

    packet[23] = stateByte; //Flags byte
    packet[24] = SBUS_FRAME_FOOTER; //Footer
}

uint8_t sbusPacket[SBUS_PACKET_LENGTH];
int rcChannels[SBUS_CHANNEL_NUMBER];
uint32_t sbusTime = 0;

void setup(){
  Serial.begin(115200);
  UART1.begin(100000, SERIAL_8N2, RX_PIN, TX_PIN);
  x8r.begin(16, 17, true, 100000);

  WiFi.begin(ssid, password);
  Serial.print("Connecting...");
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("");
  Serial.println("IP address: " + WiFi.localIP().toString());

  configCamera();

} 

void loop(){
  if(x8r.read(&mohamed[0], &failSafe, &lostFrame)){
    for (uint8_t i = 0; i < SBUS_CHANNEL_NUMBER; i++) {
      rcChannels[i] = mohamed[i];
    }
  }

  uint32_t currentMillis = millis();
  if (currentMillis > sbusTime) {
    sbusPreparePacket(sbusPacket, rcChannels, false, false);
    UART1.write(sbusPacket,SBUS_PACKET_LENGTH);
 
    sbusTime = currentMillis + SBUS_UPDATE_RATE;
  }
}

system · November 22, 2024, 9:50am

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.

Topic		Replies	Views
SoftwareSerial.h esp32 S3 Programming	13	187	October 21, 2025
ESP 32 Cam Gibberich Data output 3rd Party Boards	4	69	November 12, 2025
Tscinibuny - ESP32 Camera Robot For Arduino Solar Tracking Kit Deutsch	16	178	September 20, 2025
ESP32-C3 Super Mini tx rx not working with sda/scl 3rd Party Boards	13	701	July 12, 2025
Esp32 cam non carica Hardware	6	112	August 16, 2025

Issue with SBUS Signal Transmission on ESP32-CAM Using SoftSerial

Related topics