1.5. ESP32 外设驱动

本章介绍 ESP32 常用外设的驱动方法。

1.5.1. UART 串口

#include "driver/uart.h"
#include "driver/gpio.h"

#define UART_NUM   UART_NUM_1
#define TXD_PIN    GPIO_NUM_17
#define RXD_PIN    GPIO_NUM_16
#define BUF_SIZE   1024

void uart_init(void)
{
    const 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_DISABLE,
        .source_clk = UART_SCLK_DEFAULT,
    };

    uart_param_config(UART_NUM, &uart_config);
    uart_set_pin(UART_NUM, TXD_PIN, RXD_PIN,
                 UART_PIN_NO_CHANGE, UART_PIN_NO_CHANGE);
    uart_driver_install(UART_NUM, BUF_SIZE * 2, 0, 0, NULL, 0);
}

void uart_send(const char *data)
{
    uart_write_bytes(UART_NUM, data, strlen(data));
}

int uart_recv(char *buf, size_t len)
{
    return uart_read_bytes(UART_NUM, buf, len, pdMS_TO_TICKS(100));
}

1.5.2. I2C

#include "driver/i2c.h"

#define I2C_MASTER_SCL    GPIO_NUM_22
#define I2C_MASTER_SDA    GPIO_NUM_21
#define I2C_MASTER_FREQ   100000   // 100 kHz

void i2c_init(void)
{
    i2c_config_t conf = {
        .mode = I2C_MODE_MASTER,
        .sda_io_num = I2C_MASTER_SDA,
        .scl_io_num = I2C_MASTER_SCL,
        .sda_pullup_en = GPIO_PULLUP_ENABLE,
        .scl_pullup_en = GPIO_PULLUP_ENABLE,
        .master.clk_speed = I2C_MASTER_FREQ,
    };
    i2c_param_config(I2C_NUM_0, &conf);
    i2c_driver_install(I2C_NUM_0, I2C_MODE_MASTER, 0, 0, 0);
}

esp_err_t i2c_write_reg(uint8_t dev_addr,
                        uint8_t reg_addr, uint8_t data)
{
    uint8_t buf[] = {reg_addr, data};
    return i2c_master_write_to_device(
        I2C_NUM_0, dev_addr, buf, 2, pdMS_TO_TICKS(100));
}

uint8_t i2c_read_reg(uint8_t dev_addr, uint8_t reg_addr)
{
    uint8_t data;
    i2c_master_write_read_device(
        I2C_NUM_0, dev_addr, &reg_addr, 1,
        &data, 1, pdMS_TO_TICKS(100));
    return data;
}

1.5.3. SPI

#include "driver/spi_master.h"

#define SPI_MOSI    GPIO_NUM_23
#define SPI_MISO    GPIO_NUM_19
#define SPI_SCLK    GPIO_NUM_18
#define SPI_CS      GPIO_NUM_5

spi_device_handle_t spi;

void spi_init(void)
{
    spi_bus_config_t buscfg = {
        .mosi_io_num = SPI_MOSI,
        .miso_io_num = SPI_MISO,
        .sclk_io_num = SPI_SCLK,
        .quadwp_io_num = -1,
        .quadhd_io_num = -1,
        .max_transfer_sz = 4096,
    };

    spi_device_interface_config_t devcfg = {
        .clock_speed_hz = 10 * 1000 * 1000,  // 10 MHz
        .mode = 0,
        .spics_io_num = SPI_CS,
        .queue_size = 1,
    };

    spi_bus_initialize(SPI2_HOST, &buscfg, SPI_DMA_CH_AUTO);
    spi_bus_add_device(SPI2_HOST, &devcfg, &spi);
}

void spi_transmit(uint8_t *tx, uint8_t *rx, size_t len)
{
    spi_transaction_t t = {
        .length = len * 8,
        .tx_buffer = tx,
        .rx_buffer = rx,
    };
    spi_device_transmit(spi, &t);
}

1.5.4. I2S（音频/I2S 数字音频）

#include "driver/i2s_std.h"

void i2s_init(void)
{
    i2s_chan_handle_t tx_handle;

    i2s_chan_config_t chan_cfg = {
        .id = I2S_NUM_0,
        .role = I2S_ROLE_MASTER,
        .dma_desc_num = 6,
        .dma_frame_num = 240,
    };

    i2s_std_config_t std_cfg = {
        .clk_cfg = {
            .sample_rate_hz = 44100,
            .clk_src = I2S_CLK_SRC_DEFAULT,
            .mclk_multiple = I2S_MCLK_MULTIPLE_256,
        },
        .slot_cfg = {
            .data_bit_width = I2S_DATA_BIT_WIDTH_16BIT,
            .slot_bit_width = I2S_SLOT_BIT_WIDTH_AUTO,
            .slot_mode = I2S_SLOT_MODE_MONO,
        },
        .gpio_cfg = {
            .mclk = GPIO_NUM_0,
            .bclk = GPIO_NUM_4,
            .ws = GPIO_NUM_5,
            .dout = GPIO_NUM_18,
            .din = GPIO_NUM_19,
        },
    };

    i2s_new_channel(&chan_cfg, &tx_handle, NULL);
    i2s_channel_init_std_mode(tx_handle, &std_cfg);
    i2s_channel_enable(tx_handle);
}

1.5.5. ADC

#include "driver/adc.h"
#include "esp_adc_cal.h"

#define ADC_CHANNEL  ADC1_CHANNEL_6  // GPIO34
#define ADC_WIDTH    ADC_WIDTH_BIT_12
#define ADC_ATTEN    ADC_ATTEN_DB_11  // 0~3.3V

static esp_adc_cal_characteristics_t adc_chars;

void adc_init(void)
{
    adc1_config_width(ADC_WIDTH);
    adc1_config_channel_atten(ADC_CHANNEL, ADC_ATTEN);
    esp_adc_cal_characterize(
        ADC_UNIT_1, ADC_ATTEN, ADC_WIDTH, 3300, &adc_chars);
}

uint32_t adc_read_raw(void)
{
    return adc1_get_raw(ADC_CHANNEL);
}

uint32_t adc_read_voltage(void)
{
    uint32_t raw = adc1_get_raw(ADC_CHANNEL);
    return esp_adc_cal_raw_to_voltage(raw, &adc_chars);
}

小心

ADC2 引脚在 WiFi 启用时不可用（WiFi 驱动占用了 ADC2 的硬件资源）。 使用 ADC 时优先选择 ADC1 通道（GPIO32~39）。