如何通过 MISO 引脚使用 stm32f103（主）获取 nRF24l01（从）寄存器数据

Question

I'm trying to make a custom library for nRF24l01 for a stm32f103 target device, and I am writing code for a primary TX device. And here I'm trying to read the register contents of nRF by sending the R_REGISTER command along with the address I am looking for, but I'm not able to figure out how to read the data after the R_REGISTER command is transmitted.

And i'm using the standard stm32f10x.h header file which comes along with startup files on Kiel uVision5.

Here are the configurations,

clock setup

RCC->CR |= RCC_CR_HSION;    //HSI on
while( !(RCC_CR_HSIRDY & (RCC->CR)) );  //wait till its ready
//clocks for peripherals 
RCC->APB2ENR |= RCC_APB2ENR_IOPAEN; //enable clock forport A
RCC->APB2ENR |= RCC_APB2ENR_AFIOEN; //enable clock for alternate functions
RCC->APB2ENR |= RCC_APB2ENR_SPI1EN; //enable clock for SPI1

GPIO setup these are my custom-defined functions, they just work fine

//GPIO pin setup as alternate function
pin_mode(IOPA, GPIOA, 7, op_50MHz, op_afpp);    //MOSI pin as GPIO alternate_pin can run upto 50MHz
pin_mode(IOPA, GPIOA, 6, ip, ip_pupd);  //MISO pin as GPIO alternate_pin can run upto 50MHz
pin_mode(IOPA, GPIOA, 5, op_50MHz, op_afpp);    //SCK pin as GPIO alternate_pin can run upto 50MHz
pin_mode(IOPA, GPIOA, 4, op_50MHz, op_gppp);    //CS pin as GPIO general_puspose_pin can run upto 50MHz

SPI setup

SPI1->CR1 |= SPI_CR1_MSTR;  //master mode
SPI1->CR1 |= SPI_CR1_BR_0 | SPI_CR1_BR_1 | SPI_CR1_BR_2;    //at 571Kbps, max 31Mbps
SPI1->CR1 |= SPI_CR1_SSI;   //Software slave management enabled
SPI1->CR2 |= SPI_CR2_SSOE;  //SS o/p enable
SPI1->CR1 |= SPI_CR1_SPE;   //turn on the SPI

Im stuck here

uint8_t SPI_read_uint8_t(uint8_t addr){
    uint8_t reg_val;
    //sending the read command first along with address where we are reading from
    delay_us(50);
    digital_writepin(GPIOA, 4, LOW);
    SPI1->DR = (R_REGISTER | addr);  //sending the R_REGISTER command along with address
    while( (SPI1->SR) & (SPI_SR_BSY) );

    //please help here, how do I read the Register data from MISO pin  

Answer 1

uint8_t spi_read_write(uint8_t data)
{
    while(SPI1 -> SR & SPI_SR_RXNE) (void)*(volatile uint8_t *)&SPI1 -> DR;   //clean the FIFO
    *(volatile uint8_t *)&SPI1 -> DR = data;
    while(!(SPI1 -> SR & SPI_SR_RXNE));
    return *(volatile uint8_t *)&SPI1 -> DR;
}

uint8_t youroperation(uint8_t command, uint16_t *data)
{
    uint8_t status;
    setCSLine();
    status = spi_read_write(command);
    *data = spi_read_write(0);
    *data |= ((uint16_t)spi_read_write(0)) << 8;
    clearCSLine();   
    return status
}

youroperation will return Sn status register command parameter means Cn command bits data will contain the Dx data bits

To read data from SPI slave you need to send dummy bytes because master provides the clock for the slave.