spincoat-plater-firmware/main/spincoat-plater-firmware.c

/*
 * SPDX-FileCopyrightText: 2021-2022 Espressif Systems (Shanghai) CO LTD
 *
 * SPDX-License-Identifier: Unlicense OR CC0-1.0
 */

#include <inttypes.h>

#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "esp_log.h"
#include "driver/rmt_tx.h"
#include "driver/uart.h"
#include "dshot_esc_encoder.h"

#if CONFIG_IDF_TARGET_ESP32H2
#define DSHOT_ESC_RESOLUTION_HZ 32000000 // 32MHz resolution, DSHot protocol needs a relative high resolution
#else
#define DSHOT_ESC_RESOLUTION_HZ 40000000 // 40MHz resolution, DSHot protocol needs a relative high resolution
#endif
#define GPIO_ESC_CTRL CONFIG_ESC_CTRL_PIN
#define GPIO_ESC_RX   CONFIG_TELEMETRY_RX_PIN
#define UART_NUM      UART_NUM_2

#define ESP_INTR_FLAG_DEFAULT        0

static const char *TAG = "spincoat-plater-firmware";

//static QueueHandle_t gpio_evt_queue = NULL;
static QueueHandle_t uart_queue = NULL;
const int uart_buffer_size = (1024 * 2);

rmt_encoder_handle_t dshot_encoder = NULL;
rmt_channel_handle_t esc_chan = NULL;

rmt_transmit_config_t tx_config = {
    .loop_count = 0,
};

dshot_esc_throttle_t throttle = {
    .throttle = 0,
    .telemetry_req = false, // telemetry is not supported in this example
};

/**
 * Sends a telemetry packet at a set, constant interval
 */
void v_telemetry_packet_func(void *pvParameters) {
    TickType_t frequency = 10 / portTICK_PERIOD_MS;
    TickType_t last_wake_time = xTaskGetTickCount();
    while(1) {
        throttle.telemetry_req = true;
        vTaskDelayUntil(&last_wake_time, frequency);
    }
}

/**
 * Sends zero throttle to arm ESC for control. Stop/delete this task once the ESC has armed.
 */
void v_initialize_esc_throttle_func(void *pvParameters) {
    while(1) {
        ESP_ERROR_CHECK(rmt_transmit(esc_chan, dshot_encoder, &throttle, sizeof(throttle), &tx_config));
    }
}

/**
 * Starts task *v_initialize_esc_throttle_func()* for a few seconds and then destroys it.
 * This function takes care of the arming stage of ESC control.
 */
void initialize_esc_throttle(void) {
    TaskHandle_t v_init_throttle_handle = NULL;
    xTaskCreate(&v_initialize_esc_throttle_func, "v_init_throttle_func", 2048, NULL, 5, &v_init_throttle_handle);
    vTaskDelay(pdMS_TO_TICKS(5000));
    vTaskDelete(v_init_throttle_handle);
}

/**
 * Initialize the RMT system in preparation for sending DSHOT packets to the connected ESC.
 */
void init_rmt_esc_tx(void) {
    ESP_LOGI(TAG, "Create RMT TX channel");
    rmt_tx_channel_config_t tx_chan_config = {
        .clk_src = RMT_CLK_SRC_DEFAULT, // select a clock that can provide needed resolution
        .gpio_num = GPIO_ESC_CTRL,
        .mem_block_symbols = 64,
        .resolution_hz = DSHOT_ESC_RESOLUTION_HZ,
        .trans_queue_depth = 10, // set the number of transactions that can be pending in the background
    };
    ESP_ERROR_CHECK(rmt_new_tx_channel(&tx_chan_config, &esc_chan));

    ESP_LOGI(TAG, "Install Dshot ESC encoder");
    dshot_esc_encoder_config_t encoder_config = {
        .resolution = DSHOT_ESC_RESOLUTION_HZ,
        .baud_rate = 300000, // DSHOT300 protocol
        .post_delay_us = 50, // extra delay between each frame
    };
    ESP_ERROR_CHECK(rmt_new_dshot_esc_encoder(&encoder_config, &dshot_encoder));

    ESP_LOGI(TAG, "Enable RMT TX channel");
    ESP_ERROR_CHECK(rmt_enable(esc_chan));

    ESP_LOGI(TAG, "Start ESC by sending zero throttle for a while...");
    initialize_esc_throttle();
}

void init_telemetry_uart_rx(void) {
    uart_config_t uart_config = {
        .baud_rate = 115200,
        .data_bits = UART_DATA_8_BITS,
        .parity = UART_PARITY_DISABLE,
        .stop_bits = UART_STOP_BITS_1,
        .flow_ctrl = UART_HW_FLOWCTRL_CTS_RTS,
        .rx_flow_ctrl_thresh = 122,
    };
    
    ESP_ERROR_CHECK(uart_driver_install(UART_NUM, uart_buffer_size, uart_buffer_size, 10, &uart_queue, 0));
    ESP_ERROR_CHECK(uart_param_config(UART_NUM, &uart_config));
    ESP_ERROR_CHECK(uart_set_pin(UART_NUM, UART_PIN_NO_CHANGE, GPIO_ESC_RX, UART_PIN_NO_CHANGE, UART_PIN_NO_CHANGE));
}

/**
 * Sends a DSHOT packet via the RMT. Make sure the RMT channel has been initialized
 * by calling *init_rmt_esc_tx()*
 */
void send_dshot_packet(void) {
    ESP_ERROR_CHECK(rmt_transmit(esc_chan, dshot_encoder, &throttle, sizeof(throttle), &tx_config));
    
    if(throttle.telemetry_req == true) {
        throttle.telemetry_req = false;
    }
}

/**
 * Calculate one step of the crc8 and return it
 */
uint8_t update_crc8(uint8_t crc, uint8_t crc_seed){
    uint8_t crc_u, i;
    crc_u = crc;
    crc_u ^= crc_seed;
    for ( i=0; i<8; i++) crc_u = ( crc_u & 0x80 ) ? 0x7 ^ ( crc_u << 1 ) : ( crc_u << 1 );
    return (crc_u);
}

/**
 * Calculate the entire crc8 for a KISS frame and return it for validation against the
 * transmitted crc8
 */
uint8_t get_crc8(uint8_t *Buf, uint8_t BufLen){
    uint8_t crc = 0, i;
    for( i=0; i<BufLen; i++) crc = update_crc8(Buf[i], crc);
    return (crc);
}

/**
 * Parse the KISS telemetry frame and check the crc8
 * TODO: Do more with the data than print it
 */
void parse_telemetry(void) {
    uint8_t frame_size = 10;
    uint8_t data[128];
    // get data
    uint8_t length = uart_read_bytes(UART_NUM, data, frame_size, 100);
    
    uart_flush(UART_NUM);

    if(length < 10) return;
    
    // chop out just the payload
    uint8_t payload[128];
    uint8_t payload_length = (frame_size - 1);
    for(uint8_t i = 0; i < payload_length; i++) {
        payload[i] = data[i];
    }
    
    // calculate the crc8
    uint8_t expected_crc8 = get_crc8(payload, payload_length);
    uint8_t received_crc8 = (uint8_t) data[frame_size - 1];
    
    if(expected_crc8 != received_crc8) return;
    
    for(uint8_t i = 0; i < length; i++) {
        printf("%d - %d\n", i, data[i]);
    }
    printf("--------------------\n");
    printf("expected: %d\n", expected_crc8);
    printf("received: %d\n", received_crc8);
    printf("======================\n");
}

void app_main(void) {
    init_rmt_esc_tx();
    throttle.throttle = 300;
    
    xTaskCreate(&v_telemetry_packet_func, "v_telemetry_packet_func", 2048, NULL, 1, NULL);

    init_telemetry_uart_rx();

    while(1) {
        send_dshot_packet();
        
        uint8_t length = 0;
        ESP_ERROR_CHECK(uart_get_buffered_data_len(UART_NUM, (size_t*)&length));
        
        if(length >= 10) {
            parse_telemetry();
        }
    }
}