mcp3208 & SPI axoloti

/*
MCP3208 script2 code
by paul

Connect the MCP3208 CS pin to the NSS(PA4) or any other digital out pin of axoloti.
In this example, the MCP3208 CS pin is connected to axoloti B0(GPIOB,0) pin.

If you use more then one spi device, it's importent to disable every other spi device by switching their cs pin.
*/

uint8_t *txbuf;
uint8_t *rxbuf;

void setup(void){
    static uint8_t _txbuf[8] __attribute__ ((section (".sram2")));
    static uint8_t _rxbuf[8] __attribute__ ((section (".sram2")));
    txbuf = _txbuf;
    rxbuf = _rxbuf;

    palSetPadMode(GPIOA,0,PAL_MODE_OUTPUT_PUSHPULL);    // MCP3208
    palWritePad(GPIOA,0,1);                             // pull high to disable first MCP3208
}

void loop(void){
    // txtbuf[0] = txtbuf[1] = txtbuf[2] = 0b00000000;
    txbuf[2] = 0b00000000;

        for(int pin=0; pin<8; pin++){

            txbuf[0] = pin < 4 ? 0b01100000 : 0b11100000;

            if (pin % 4 == 0) { // pin == 0 || pin == 4
                txbuf[1] = 0b00000000;
            } else if (pin % 4 == 1) { // pin == 1 || pin == 5
                txbuf[1] = 0b00000010;
            } else if (pin % 4 == 2) { // pin == 2 || pin == 6
                txbuf[1] = 0b00000001;
            } else {
                txbuf[1] = 0b00000011;
            }


        palWritePad(GPIOA,0,0);     // enable MCP3208
        spiSelect(&SPID1);          // START SPI
        spiSend(&SPID1,3,txbuf);    // send SPI data txbuf[]
        spiReceive(&SPID1,3,rxbuf); // receive SPI data from MCP3208
        spiUnselect(&SPID1);        // STOP SPI
        palWritePad(GPIOA,0,1);     // disable MCP3208

        int z = (rxbuf[1] << 8| rxbuf[0]) << 16;

        if (pin == 0){
            PExParameterChange(&parent->PExch[PARAM_INDEX_c0_value],z,0xFFFD);
        }
        else if (pin == 1){
            PExParameterChange(&parent->PExch[PARAM_INDEX_c1_value],z,0xFFFD);
        }
        else if (pin == 2){
            PExParameterChange(&parent->PExch[PARAM_INDEX_c2_value],z,0xFFFD);
        }
        else if (pin == 3){
            PExParameterChange(&parent->PExch[PARAM_INDEX_c3_value],z,0xFFFD);
        }
        else if (pin == 4){
            PExParameterChange(&parent->PExch[PARAM_INDEX_c4_value],z,0xFFFD);
        }
        else if (pin == 5){
            PExParameterChange(&parent->PExch[PARAM_INDEX_c5_value],z,0xFFFD);
        }
        else if (pin == 6){
            PExParameterChange(&parent->PExch[PARAM_INDEX_c6_value],z,0xFFFD);
        }
        else if (pin == 7){
            PExParameterChange(&parent->PExch[PARAM_INDEX_c7_value],z,0xFFFD);
        }
    }
    chThdSleepMilliseconds(1);
}