SPI Sending and Receiving Extra Bytes
I doing bare metal coding for STM32L496ZGT6. Now in SPI, extra bytes are sent. There are only 4 Registers in SPI but unable to resolve the issue. Below is my code
NOTE:
I am using Aardwark Total Phase Control Center software for debugging. I am attaching the related images. The Chip select to be handled by the SPI Hardware.
Data sheet is DS11585.
#include "lib_headers.h"
#define SPI1EN (1U << 12)
#define GPIOAEN (1U << 0)
#define SR_TXE (1U << 1)
#define SR_RXNE (1U << 0)
#define SR_BSY (1U << 7)
const char write_data[] = "ABCD"; // Data to write (4 bytes)
char read_data[5] = {0}; // Buffer to store received data (4 bytes + null terminator)
uint8_t reg_address = 0x01; // Example register address
void delay(volatile uint32_t count) {
while (count--);
}
void spi1_transmit(uint8_t *data, uint32_t size) {
uint32_t i = 0;
while (i < size) {
while (!(SPI1->SR & SR_TXE)) {}
SPI1->DR = data[i++];
}
while (!(SPI1->SR & SR_TXE)) {}
while (SPI1->SR & SR_BSY) {}
(void)SPI1->DR;
(void)SPI1->SR;
}
void spi1_receive(uint8_t *data, uint32_t size)
{
while (size--) {
SPI1->DR = 0xFF;
while (!(SPI1->SR & SR_TXE)) {}
while (!(SPI1->SR & SR_RXNE)) {}
*data++ = SPI1->DR;
}
}
int main(void)
{
set_sysclk_to_msi(MSI_16MHZ);
uart2_config(9600);
Initialize_LED_GPIOs();
/* Enable GPIO clocks */
RCC->AHB2ENR |= GPIOAEN | (1 << 1); // Enable GPIOA and GPIOB
/* Enable SPI1 clock */
RCC->APB2ENR |= SPI1EN; // SPI1 clock enable
// Configure PA5, PA6, PA7 for SPI1 (SCK, MISO, MOSI)
GPIOA->MODER &= ~((3 << 10) | (3 << 12) | (3 << 14)); // Clear modes
GPIOA->MODER |= (2 << 10) | (2 << 12) | (2 << 14); // Set alternate mode
GPIOA->AFR[0] |= (5 << 20) | (5 << 24) | (5 << 28); // AF5 for SPI1
// Configure PA4 for SPI1_NSS (CS) (This can remain as an alternate function pin)
GPIOA->MODER &= ~(3 << 8); // Clear mode for PA4
GPIOA->MODER |= (2 << 8); // Set PA4 to alternate function mode
GPIOA->AFR[0] |= (5 << 16); // AF5 for SPI1_NSS
SPI1->CR1 = 0; // Clear all settings
/* Disable SPI before configuration */
SPI1->CR1 &= ~(1 << 6); // Disable SPI
/* Configure SPI1 in master mode */
SPI1->CR1 |= (0 << 0) | (0 << 1); // CPOL = 0, CPHA = 0
SPI1->CR1 |= (3 << 3); // Baud rate (fPCLK/16) for 1 MHz
SPI1->CR1 |= (0 << 10); // Full duplex communication
SPI1->CR1 |= (0 << 13); // CRC disabled
SPI1->CR1 &= ~(1U << 10); // Enable full duplex
SPI1->CR1 &= ~(1U << 7); // Set MSB first
SPI1->CR1 |= (1U << 2); // Set mode to MASTER
SPI1->CR1 &= ~(1U << 11); // Set 8-bit data mode
/* Configure frame size and RX FIFO threshold */
SPI1->CR2 = 0;
SPI1->CR2 |= (1 << 2); // SSOE = 1 (SS output enable)
SPI1->CR2 |= (0 << 3) | (0 << 4); // Motorola frame format, manual CS..no need for SPI to generate clock pulse
SPI1->CR2 |= (7 << 8); // Data size to 8 bits
/* Enable SPI */
SPI1->CR1 |= (1 << 6);
// Transmit data over SPI
spi1_transmit((uint8_t *)write_data, sizeof(write_data) - 1); // Exclude null terminator
// Receive data over SPI
spi1_receive((uint8_t *)read_data, sizeof(read_data) - 1); // Read only 4 bytes
// Transmit received data over UART
uart2_send_string(read_data, sizeof(read_data) - 1); // Send only the received data
uart2_send_string("\r\n", 2);
while (1) {
}
return 0;
}
I want to know the 00 or FF is stuffed for every byte sent or received.