/* ------------------------------------------------------------------------- Simple Arduino trasmisster (PPM to ELRS) Decode PPM to CRSF protocol Arduino Nano ELRS 2.4G TX moduel Custom PCB from JLCPCB https://github.com/kkbin505/Arduino-Transmitter-for-ELRS */ //default channel order is AETR int values[16]; #define u8 uint8_t #define TAER #define RADIO_ADDRESS 0xEA #define ADDR_MODULE 0xEE // Crossfire transmitter #define TYPE_CHANNELS 0x16 // internal crsf variables #define CRSF_CHANNEL_MIN 172 #define CRSF_CHANNEL_MID 991 #define CRSF_CHANNEL_MAX 1811 #define CRSF_TIME_NEEDED_PER_FRAME_US 1100 // 700 ms + 400 ms for potential ad-hoc request #define CRSF_TIME_BETWEEN_FRAMES_US 4000 // 4 ms 250Hz #define CRSF_PAYLOAD_OFFSET offsetof(crsfFrameDef_t, type) #define CRSF_MAX_CHANNEL 16 #define CRSF_FRAME_SIZE_MAX 64 #define SERIAL_BAUDRATE 420000 #define CRSF_MSP_RX_BUF_SIZE 128 #define CRSF_MSP_TX_BUF_SIZE 128 #define CRSF_PAYLOAD_SIZE_MAX 60 #define CRSF_PACKET_LENGTH 22 #define CRSF_PACKET_SIZE 26 #define CRSF_FRAME_LENGTH 24; // length of type + payload + crc uint8_t crsfPacket[CRSF_PACKET_SIZE]; int rcChannels[CRSF_MAX_CHANNEL]; uint32_t crsfTime = 0; enum chan_order{ THROTTLE, AILERON, ELEVATOR, RUDDER, AUX1, // (CH5) ARM switch for Expresslrs AUX2, // (CH6) angel / airmode change AUX3, // (CH7) flip after crash AUX4, // (CH8) AUX5, // (CH9) AUX6, // (CH10) AUX7, // (CH11) AUX8, // (CH12) }; #include #include #define SCREEN_WIDTH 128 // OLED display width, in pixels #define SCREEN_HEIGHT 64 // OLED display height, in pixels // Declaration for an SSD1306 display connected to I2C (SDA, SCL pins) // The pins for I2C are defined by the Wire-library. // On an arduino UNO: A4(SDA), A5(SCL) // On an arduino MEGA 2560: 20(SDA), 21(SCL) // On an arduino LEONARDO: 2(SDA), 3(SCL), ... #define OLED_RESET 4 // Reset pin # (or -1 if sharing Arduino reset pin) #define SCREEN_ADDRESS 0x3D ///< See datasheet for Address; 0x3D for 128x64, 0x3C for 128x32 Adafruit_SSD1306 display = Adafruit_SSD1306(128, 64, &Wire); void setup() { for (uint8_t i = 0; i < CRSF_MAX_CHANNEL; i++) { rcChannels[i] = CRSF_CHANNEL_MID; } rcChannels[THROTTLE] = CRSF_CHANNEL_MIN; // Throttle delay(1000); Serial1.begin(SERIAL_BAUDRATE); Serial.begin(115200); // while (!Serial) { // some boards need to wait to ensure access to serial over USB //} display.begin(SSD1306_SWITCHCAPVCC, 0x3C); // Address 0x3C for 128x32 display.clearDisplay(); // start the screen } int n; void loop() { static unsigned long looptime; uint32_t currentMicros = micros(); if (currentMicros > crsfTime) { crsfPreparePacket(crsfPacket, rcChannels); Serial1.write(crsfPacket, CRSF_PACKET_SIZE); crsfTime = currentMicros + CRSF_TIME_BETWEEN_FRAMES_US; } if (millis() > looptime + 19) { looptime = millis(); n++; if (n > 511) n = 0; display.clearDisplay(); display.setCursor(0, 0); // Start at top-left corner display.setTextSize(1); // Draw 2X-scale text display.setTextColor(SSD1306_WHITE); display.println(F("12345678 transmitted")); for (int i = 0; i < 16; i++) { // the used channels) values[i] = 64 + 64 * sin(10 * 6.28 * n / 512.0 + 12 * i); display.fillRect(i * 6, 32 -values[i] / 8, 4, 32, SSD1306_INVERSE); rcChannels[i] = map(values[i],0,127,CRSF_CHANNEL_MIN,CRSF_CHANNEL_MAX); } display.display(); } } // loop // crc implementation from CRSF protocol document rev7 static u8 crsf_crc8tab[256] = { 0x00, 0xD5, 0x7F, 0xAA, 0xFE, 0x2B, 0x81, 0x54, 0x29, 0xFC, 0x56, 0x83, 0xD7, 0x02, 0xA8, 0x7D, 0x52, 0x87, 0x2D, 0xF8, 0xAC, 0x79, 0xD3, 0x06, 0x7B, 0xAE, 0x04, 0xD1, 0x85, 0x50, 0xFA, 0x2F, 0xA4, 0x71, 0xDB, 0x0E, 0x5A, 0x8F, 0x25, 0xF0, 0x8D, 0x58, 0xF2, 0x27, 0x73, 0xA6, 0x0C, 0xD9, 0xF6, 0x23, 0x89, 0x5C, 0x08, 0xDD, 0x77, 0xA2, 0xDF, 0x0A, 0xA0, 0x75, 0x21, 0xF4, 0x5E, 0x8B, 0x9D, 0x48, 0xE2, 0x37, 0x63, 0xB6, 0x1C, 0xC9, 0xB4, 0x61, 0xCB, 0x1E, 0x4A, 0x9F, 0x35, 0xE0, 0xCF, 0x1A, 0xB0, 0x65, 0x31, 0xE4, 0x4E, 0x9B, 0xE6, 0x33, 0x99, 0x4C, 0x18, 0xCD, 0x67, 0xB2, 0x39, 0xEC, 0x46, 0x93, 0xC7, 0x12, 0xB8, 0x6D, 0x10, 0xC5, 0x6F, 0xBA, 0xEE, 0x3B, 0x91, 0x44, 0x6B, 0xBE, 0x14, 0xC1, 0x95, 0x40, 0xEA, 0x3F, 0x42, 0x97, 0x3D, 0xE8, 0xBC, 0x69, 0xC3, 0x16, 0xEF, 0x3A, 0x90, 0x45, 0x11, 0xC4, 0x6E, 0xBB, 0xC6, 0x13, 0xB9, 0x6C, 0x38, 0xED, 0x47, 0x92, 0xBD, 0x68, 0xC2, 0x17, 0x43, 0x96, 0x3C, 0xE9, 0x94, 0x41, 0xEB, 0x3E, 0x6A, 0xBF, 0x15, 0xC0, 0x4B, 0x9E, 0x34, 0xE1, 0xB5, 0x60, 0xCA, 0x1F, 0x62, 0xB7, 0x1D, 0xC8, 0x9C, 0x49, 0xE3, 0x36, 0x19, 0xCC, 0x66, 0xB3, 0xE7, 0x32, 0x98, 0x4D, 0x30, 0xE5, 0x4F, 0x9A, 0xCE, 0x1B, 0xB1, 0x64, 0x72, 0xA7, 0x0D, 0xD8, 0x8C, 0x59, 0xF3, 0x26, 0x5B, 0x8E, 0x24, 0xF1, 0xA5, 0x70, 0xDA, 0x0F, 0x20, 0xF5, 0x5F, 0x8A, 0xDE, 0x0B, 0xA1, 0x74, 0x09, 0xDC, 0x76, 0xA3, 0xF7, 0x22, 0x88, 0x5D, 0xD6, 0x03, 0xA9, 0x7C, 0x28, 0xFD, 0x57, 0x82, 0xFF, 0x2A, 0x80, 0x55, 0x01, 0xD4, 0x7E, 0xAB, 0x84, 0x51, 0xFB, 0x2E, 0x7A, 0xAF, 0x05, 0xD0, 0xAD, 0x78, 0xD2, 0x07, 0x53, 0x86, 0x2C, 0xF9}; u8 crsf_crc8(const u8 *ptr, u8 len) { u8 crc = 0; for (u8 i=0; i < len; i++) { crc = crsf_crc8tab[crc ^ *ptr++]; } return crc; } void crsfPreparePacket(uint8_t packet[], int channels[]){ static int output[CRSF_MAX_CHANNEL] = {0}; const uint8_t crc = crsf_crc8(&packet[2], CRSF_PACKET_SIZE-3); /* * Map 1000-2000 with middle at 1500 chanel values to * 173-1811 with middle at 992 S.BUS protocol requires */ for (uint8_t i = 0; i < CRSF_MAX_CHANNEL; i++) { output[i] = channels[i]; } /* Serial.print("crsf "); Serial.print(output[0]); Serial.print(" i"); Serial.print(output[1]); Serial.print(" i"); Serial.print(output[2]); Serial.print(" i"); Serial.print(output[3]); Serial.println(); */ // packet[0] = UART_SYNC; //Header packet[0] = ADDR_MODULE; //Header packet[1] = 24; // length of type (24) + payload + crc packet[2] = TYPE_CHANNELS; packet[3] = (uint8_t) (channels[0] & 0x07FF); packet[4] = (uint8_t) ((channels[0] & 0x07FF)>>8 | (channels[1] & 0x07FF)<<3); packet[5] = (uint8_t) ((channels[1] & 0x07FF)>>5 | (channels[2] & 0x07FF)<<6); packet[6] = (uint8_t) ((channels[2] & 0x07FF)>>2); packet[7] = (uint8_t) ((channels[2] & 0x07FF)>>10 | (channels[3] & 0x07FF)<<1); packet[8] = (uint8_t) ((channels[3] & 0x07FF)>>7 | (channels[4] & 0x07FF)<<4); packet[9] = (uint8_t) ((channels[4] & 0x07FF)>>4 | (channels[5] & 0x07FF)<<7); packet[10] = (uint8_t) ((channels[5] & 0x07FF)>>1); packet[11] = (uint8_t) ((channels[5] & 0x07FF)>>9 | (channels[6] & 0x07FF)<<2); packet[12] = (uint8_t) ((channels[6] & 0x07FF)>>6 | (channels[7] & 0x07FF)<<5); packet[13] = (uint8_t) ((channels[7] & 0x07FF)>>3); packet[14] = (uint8_t) ((channels[8] & 0x07FF)); packet[15] = (uint8_t) ((channels[8] & 0x07FF)>>8 | (channels[9] & 0x07FF)<<3); packet[16] = (uint8_t) ((channels[9] & 0x07FF)>>5 | (channels[10] & 0x07FF)<<6); packet[17] = (uint8_t) ((channels[10] & 0x07FF)>>2); packet[18] = (uint8_t) ((channels[10] & 0x07FF)>>10 | (channels[11] & 0x07FF)<<1); packet[19] = (uint8_t) ((channels[11] & 0x07FF)>>7 | (channels[12] & 0x07FF)<<4); packet[20] = (uint8_t) ((channels[12] & 0x07FF)>>4 | (channels[13] & 0x07FF)<<7); packet[21] = (uint8_t) ((channels[13] & 0x07FF)>>1); packet[22] = (uint8_t) ((channels[13] & 0x07FF)>>9 | (channels[14] & 0x07FF)<<2); packet[23] = (uint8_t) ((channels[14] & 0x07FF)>>6 | (channels[15] & 0x07FF)<<5); packet[24] = (uint8_t) ((channels[15] & 0x07FF)>>3); packet[25] = crsf_crc8(&packet[2], CRSF_PACKET_SIZE-3); //CRC }