STM32 F411RE Nucleo SPI support and programming the PlayStation 2 controller - c

Question

For a few days I have been trying to get the correct answer from the PS2 gamepad (DualShock 2) on the STM32F411RE Nucleo.
I use SPI and USART to receive messages.
The clock frequency is set to 8 MHz and the SPI prescaler to a 64 configuration which gives me 125 kHz (kbit/s).
The first bit is taken from LSB, the CPOL parameter at 1, and CPHA on 2. It is NSS software controlled, set to GPIO output (PA4-CS pin). I use PA5 pins as SCK (clock) PA6-MISO, PA7-MOSI. SPI is set to full-duplex master mode. (USART asynchronous and 9600 bit/s, but it's just for receiving messages on a PC).
The microcontroller operates a HAL library.
In the main.c file:
#define CS_LOW HAL_GPIO_WritePin(CS_GPIO_Port, CS_Pin, GPIO_PIN_RESET)
#define CS_HIGH HAL_GPIO_WritePin(CS_GPIO_Port, CS_Pin, GPIO_PIN_SET)
CS LOW - sets the line "attention" to state 0 and CS_HIGH to state 1.
The function sending command and return data (MISO-MOSI):
uint8_t PS2_RWByte(uint8_t komenda, uint8_t tablica, int wielkosc)
{
HAL_SPI_Transmit(&hspi1, &komenda, sizeof(komenda), 1);
HAL_SPI_Receive(&hspi1, &tablica, sizeof(tablica), 1);
return(tablica);
}
Function sending a byte string:
uint8_t Get_PS2Dat(uint8_t buf[])
{
CS_LOW;
HAL_Delay(15/1000);
buf[0] = PS2_RWByte(0x01, buf[0], 8);HAL_Delay(15/1000);
buf[1] = PS2_RWByte(0x42, buf[1], 8);HAL_Delay(15/1000);
buf[2] = PS2_RWByte(0x00, buf[2], 8);HAL_Delay(15/1000);
buf[3] = PS2_RWByte(0x00, buf[3], 8);HAL_Delay(15/1000);
buf[4] = PS2_RWByte(0x00, buf[4], 8);HAL_Delay(15/1000);
buf[5] = PS2_RWByte(0x00, buf[5], 8);HAL_Delay(15/1000);
buf[6] = PS2_RWByte(0x00, buf[6], 8);HAL_Delay(15/1000);
buf[7] = PS2_RWByte(0x00, buf[7], 8);HAL_Delay(15/1000);
buf[8] = PS2_RWByte(0x00, buf[8], 8);HAL_Delay(15/1000);
CS_HIGH;
if((buf[0] == 0xFF) && (buf[1] == 0x41) && (buf[2] == 0x5A))
return 1;
if((buf[0] == 0xFF) && (buf[1] == 0x73) && (buf[2] == 0x5A))
return 2;
return 0;
}
In the main function:
int main(void)
{
HAL_Init();
SystemClock_Config();
MX_GPIO_Init();
MX_USART2_UART_Init();
MX_SPI1_Init();
HAL_SPI_MspInit(&hspi1);
uint8_t PS2buf[10] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
uint8_t wyswietl[30] = {0};
while (1)
{
Get_PS2Dat(PS2buf);
for(int i=0; i<9; i++)
{
sprintf(wyswietl, "%u ,", PS2buf[i]);
HAL_UART_Transmit(&huart2, wyswietl, 30, 250);
}
sprintf(wyswietl, "\n\r");
HAL_UART_Transmit(&huart2, wyswietl, 30, 250);
HAL_Delay(300);
}
}
After sending the information: 0x01 0x42 0x00 0x00 0x00 I should get 0xFF 0x41 0x5A 0xFF 0xFF if no button is pressed.
At 3 and 4 bytes should appear information about the pressed keys while I get such values:
65, 255, 255, 255, 255 ie 0xFF 0xFF 0xFF 0xFF 0xFF.
It is strange how the second sent byte corresponds to the first received. The additional point is that if you press the "mode" key the value 65 changes to 115 (0x73), while others still remain unchanged.

Answer 1

You should use HAL_SPI_TransmitReceive instead of a combination of HAL_SPI_Transmit and HAL_SPI_Receive.
The function HAL_SPI_Transmit only sends data and omits incoming bytes.
The function HAL_SPI_Receive sends dummy data and fetches incoming bytes.
Basically, you are receiving every second character.
65 = 0x42 is the second character. Because you send a dummy byte when you receive data, the remaining message is not understood by the PS2 controller, so you get 0xFF.
Change your PS2_RWByte function like that and it should work:
uint8_t PS2_RWByte(uint8_t komenda, uint8_t tablica, int wielkosc)
{
HAL_SPI_TransmitReceive(&hspi1, &komenda, &tablica, sizeof(uint8_t), 1);
return(tablica);
}

Answer 2

I am not familiar with the PS2 gamepad, but I believe you have to set the NSS pin back to high after your spi-receive (so you need also set it to low before every single write...).