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HI everyone, i'm trying to do an a SPI communication between the board STM32F746 and the MAX7219 to controller a matrix. i'm working in keil uvision 5 and programming without libraries, DMA, CMSIS or other. i programm through registers putting '1'. i want a full-duplex communication, as slave and onliy are one slave. i add the code that i do. it's on spanish that is my languaje. i hope that all can understand me and solve this. thanks
// Code
/*
Pines:
PB3: SCL
PB4: MISO
PB5: MOSI
*/
// ************************ LIBRERIAS ************************
#include <stdio.h>
#include "STM32F7xx.h"
// ***********************************************************
// ************************ VARIABLES GLOBALES ***************
// ************************ FUNCIONES ************************
void enviar_datos(char comando, char dato){
char recibido=0;
// Espera mientras la busy flag esta activa
while(!(SPI3->SR & SPI_SR_TXE)){} // Mientas la busy flago esta en 1 no se
SPI3->DR=comando; //
while(SPI3->SR & SPI_SR_RXNE){} // Tiempo de espera mientras se vacia el buffer
recibido=SPI3->DR;
while(!(SPI3->SR & SPI_SR_TXE)){} // Mientas la busy flago esta en 1 no se puede tr
SPI3->DR=dato; //
}
char leer_datos(char direccion){
while(!(SPI3->SR & SPI_SR_TXE)){} // Mientas la busy flago esta en 1 no se puede
SPI3->DR=direccion; //
SPI3->DR=0x00; //
return SPI3->DR;
// ************************ INTERRUPCIONES *******************
extern "C"{
// ************************ MAIN *****************************
int main(void){
// ******************** PUERTOS **************************
RCC->AHB1ENR |=0x03; // Activo el puerto A y B
// *******************************************************
// ******************** PINES ****************************
GPIOA->MODER |=0x80000000; // Alternativo pin 15
GPIOA->AFR[1] =0x60000000; // Funcion alterna 6
GPIOB->MODER |=0xA80; // Alternativo pines 3 a 5
GPIOB->AFR[0] =0x666000; // Funcion alterna 6
// ******************** SPI ******************************
RCC->APB1ENR |=RCC_APB1ENR_SPI3EN; // Activo el Habilitador del SPI 3
SPI3->CR1 |=0x31; // Configuracion del BaudRate as 256
SPI3->CR1 |=SPI_CR1_CPHA; // Configuracion de la fase del SLC, la he
SPI3->CR1 |=SPI_CR1_CPOL; // Configuracion de la polaridad del Reloj,
SPI3->CR1 |=SPI_CR1_SSM; // Activo el asistente de slave select
SPI3->CR1 &=~SPI_CR1_RXONLY; // Configuracion para que la Full-duplex
SPI3->CR1 &=~SPI_CR1_BIDIMODE; // Configuracion para tener 2 lineas
SPI3->CR1 &=~SPI_CR1_LSBFIRST; // Configuracion para que se transmita
SPI3->CR1 |=SPI_CR1_CRCEN; // No necesito CRC
SPI3->CR1 |=SPI_CR1_MSTR; // Configuracion del SPI como MASTER
SPI3->CR1 |=SPI_CR1_SSI;
SPI3->CR1 &=~SPI_CR1_CRCL; // tamaño de 8 bits
// CR2
SPI3->CR2 |=0x700; // Configuracion del tamaño de la informacion a
SPI3->CR2 |=SPI_CR2_SSOE; // Activo el output SS para tener un unico
SPI3->CR2 &=~SPI_CR2_FRF; // SPI en modo normal
SPI3->CR2 &=~SPI_CR2_NSSP; // No deseo pulsos en la linea SS
SPI3->CR2 |=SPI_CR2_FRXTH; // Se activa la interrupcion Rx si recibe 8 bits
SPI3->CR1 |=SPI_CR1_SPE; // Activo el periferico
enviar_datos(0x04,0x00);
// ******************** MAIN *****************************
while(true){
HI, i'm sorry for put all the question in the title, i answer all of yours questions:
1. When i prove the code in the keil debugger, i hope that the registers TXFifo is the same like a transmit data in my function. I mean, if i send for example 0x08 (1 byte), in the TXFifo show 0x08, but this doesn't happen, if i send for example the same 0x08 in the tx fifo i se ... 0x1A doesn't match and i dont kwno why happens 2. this that i told you, the TxFifo doesnt match with the data transmit
3. the proof is the debugger, i show you an a debugger photo:
i send two bytes and in the debugger doesn't match. i don't know what is could be wrong, i thing that is the transmit function because the spi configuration are based on the datasheet.
It is common that you cannot read-back a Tx register:
These are not memory locations, they are "gateways" into the hardware:
As Robert McNamara said, you need to study the datasheet to understand how this works in your particular chip.
stm32f746zgtx said:the proof is the debugger
No.
The proof is to use an oscilloscope or analyser to see what is actually happening on the actual hardware lines.