AVR Freaks

Hi everyone,

I'm trying to control a MCP41100 digipot with an ATMEGA3208. I based my code on Atmel example, with the same pinout but the wiper position doesn't move at whatever value I send to it (0 to 255). Here is my simplified code for reference:

#define F_CPU 16000000
#define DIPOT_WRITE	0b00010011

#include <avr/io.h>

static void SPI0_init(void);
static uint8_t SPI0_exchangeData(uint8_t data);

static void SPI0_init(void)
{
    PORTA.DIR |= PIN4_bm; /* Set MOSI pin direction to output */
    PORTA.DIR |= PIN6_bm; /* Set SCK pin direction to output */
    PORTA.DIR |= PIN7_bm; /* Set SS pin direction to output */

    SPI0.CTRLA = SPI_ENABLE_bm          /* Enable module */
               | SPI_MASTER_bm          /* SPI module in Master mode */
               | SPI_PRESC_DIV16_gc;    /* System Clock divided by 16 */
}

static uint8_t SPI0_exchangeData(uint8_t data)
{
    
    SPI0.DATA = data;

    while (!(SPI0.INTFLAGS & SPI_IF_bm))  /* waits until data is exchanged*/
    {
        ;
    }

    return SPI0.DATA;
}

int main(void)
{
    CCP = CCP_IOREG_gc; // No clock division (full 16Mhz)
    CLKCTRL.MCLKCTRLB = 0; // No clock division (full 16Mhz)

    SPI0_init();
    
    while (1)
    {
        PORTA.OUT &= ~PIN7_bm; // Set SS pin value to LOW
        SPI0_exchangeData(DIPOT_WRITE); // Write command for the MCP41100
        SPI0_exchangeData(10); // Random value from 0 to 255
        PORTA.OUT |= PIN7_bm; // Set SS pin value to HIGH
        
    }
}

Any pointers would be much appreciated!

Thank you,

Octave