STM32L011K4 带有 DMA 使用 I2C 启动条件未发生

Question

我正在尝试使用 STM32L011K4 的 DMA 控制器通过 I2C 与从设备进行通信。 目前，我没有从设备，只是试图让微控制器将启动条件发送到 I2C 总线上，但这并没有发生。

当我通过 STM32CubeIDE 在调试模式下运行此代码时，我注意到启动位已设置，但它永远不会清除，即使参考手册说一旦启动条件发生它应该由硬件清除（I2C_CR2 的第 656 页）。

在我的示波器上监测 SDA 和 SCL 线也表明它们是逻辑 1。 注意：我在面包板上使用 NUCLEO-L011K4，所以 IO 引脚通过 1k 电阻连接到 Vref。 当代码在发送开始条件时被卡住时，所有配置寄存器似乎都包含所需的值，所以我不相信它们会被随机的代码行破坏。

我不确定是什么阻止了开始条件的发送，因此我们将不胜感激。

STM32L011K4 数据表： https ://www.st.com/content/ccc/resource/technical/document/datasheet/42/c0/ab/e5/71/7a/47/0b/DM00206508.pdf/files/DM00206508.pdf /jcr:content/translations/en.DM00206508.pdf

STM32L011K4 参考手册： https ://www.st.com/resource/en/reference_manual/dm00108282-ultralowpower-stm32l0x1-advanced-armbased-32bit-mcus-stmicroelectronics.pdf

初始化代码：

void Init_I2C1_DMA() {
    /*  Basic I2C Initialization for 100 kHz I2C, 24 MHz SYSCLK, /1 APB1 scaler  */
    RCC->APB1ENR |= RCC_APB1ENR_I2C1EN; // Enable peripheral clock for I2C1

    I2C1->CR1 &= ~(I2C_CR1_PE);         // Disable I2C1
    I2C1->CR1 = 0;                      // Reset CR1

    I2C1->TIMINGR = 0;                  // Reset timer settings
    /* APB1 clock (I2C1 clock) is set in RCC_CFGR reg -- keep at divide by 1 -- 24 MHz SYSCLK
     * Refer to table 103 for timing value source.  t_presc was found to be 250 ns for 100 kHz I2C, so PRESC was set to match that for SYSCLK = 24 MHz
     * All subsequent settings are copied from table 103 from STM32L011K4 reference manual
     */
    I2C1->TIMINGR |= (0x5 << 28)|(0x4 << 20)|(0x2 << 16)|(0x0F << 8)|(0x13 << 0);

    /* Desired settings:
     * RXDMAEN enable, ANF enable.
     */
    I2C1->CR1 |= (0x8 << I2C_CR1_DNF_Pos)|I2C_CR1_ERRIE;
    I2C1->CR2 = 0;                      // Reset contents (ACKs are enabled by default)
    NVIC_EnableIRQ(I2C1_IRQn);
    NVIC_SetPriority(I2C1_IRQn, 0);

    /* DMA initialization */

    /* Since this is peripheral to memory, we use I2C1_RX, which is available on DMA channels 3,7.  We used channel 3, but 7 would work the same. */
    RCC->AHBENR |= RCC_AHBENR_DMA1EN;                           // Enable peripheral clock for DMA1
    DMA1_Channel3->CCR &= ~(0x00000001);                        // Disable Channel 3 DMA

    // Configure DMA channel mapping
    DMA1_CSELR->CSELR &= ~0x00000F00; // Channel 3 re-mapping mask
    DMA1_CSELR->CSELR |=  0x00000600; // Channel 3 re-mapped to I2C1_RX

    /* Configure NVIC for DMA */
    NVIC_EnableIRQ(DMA1_Channel2_3_IRQn);
    NVIC_SetPriority(DMA1_Channel2_3_IRQn, 0);

    return;
}

void I2C1_DMA_Start_Read(uint8_t SlaveAddress, uint8_t RegisterAddress, int* MemoryBaseAddress, int BufferSize) {
    // We need to put the device address out on the serial line before we can hand it over to the DMA

    I2C1->CR1 &= ~(I2C_CR1_PE);                                 // Disable I2C1
    DMA1_Channel3->CCR &= ~DMA_CCR_EN;                          // Disable Channel 3 DMA

    DMA1_Channel3->CCR &= ~(0x00007FFF);                        // Channel 3 DMA mask
    // Configure DMA Channel 3 for 16 bit memory and peripheral, and other aliased settings (reference manual page 249, 10.4.3)
    DMA1_Channel3->CCR |=  (0b01 << 10)|(0b01 << 8)|DMA_CCR_MINC|DMA_CCR_TEIE|DMA_CCR_TCIE;

    DMA1_Channel3->CPAR =  (uint32_t) RegisterAddress;
    DMA1_Channel3->CMAR =  (uint32_t) MemoryBaseAddress;
    DMA1_Channel3->CNDTR = (uint16_t) BufferSize;

    I2C1->CR1 &= (~I2C_CR1_TXDMAEN);                            // Disable TX DMA for I2C1
    I2C1->CR1 |= I2C_CR1_RXDMAEN;                               // Enable RX DMA for I2C1
    // I2C1->CR2 |= ((uint8_t) (SlaveAddress << 1));            // Set up the slave address for DMA read
    while(!(I2C1->ISR & I2C_ISR_TXE));
    I2C1->TXDR |= ((uint8_t) (SlaveAddress << 1));              // Set up the slave address for DMA read
    I2C1->CR2 |= I2C_CR2_RD_WRN;

    DMA1_Channel3->CCR |= DMA_CCR_EN;                           // Activate DMA channel 3
    I2C1->CR1 |= I2C_CR1_PE;                                    // Enable I2C1

    I2C1->CR2 |= I2C_CR2_START;                                 // Generate start condition
    while(I2C1->CR2 & I2C_CR2_START);                           // Wait until hardware clears the start bit

    // ???

    return;
}

Answer 1

根据参考手册（第 604 页），您需要取消注释I2C1->CR2 |= ((uint8_t) (SlaveAddress << 1)); 并评论I2C1->TXDR |= ((uint8_t) (SlaveAddress << 1)); 设置从机地址，需要设置要传输的字节数。

我看不到您对 GPIO 的初始化。 检查 GPIO 设置是否正确（替代功能和开漏模式）。

同样在参考手册中写了这个

为了执行软件复位，PE 必须在至少 3 个 APB 时钟周期内保持低电平。 这是通过写入以下软件序列来确保的： - 写入 PE=0 - 检查 PE=0 - 写入 PE=1。

我认为你应该尝试这样做。

另外我建议使用 4.7k 电阻来拉到 VDD。