# SPI1 - AT91SAM9G20 - external ADC

**URL:** <https://community.sparkfun.com/t/spi1-at91sam9g20-external-adc/16925>\
**Category:** MicroMod\
**Tags:** arm-lpc\
**Created:** [August 10, 2010, 9:21pm UTC](https://community.sparkfun.com/t/spi1-at91sam9g20-external-adc/16925 "2010-08-10T21:21:21Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![lnxfrk](https://avatars.discourse-cdn.com/v4/letter/l/ce73a5/32.png) [@lnxfrk](https://community.sparkfun.com/u/lnxfrk)\
**Post date:** [August 10, 2010, 9:21pm UTC](https://community.sparkfun.com/t/spi1-at91sam9g20-external-adc/16925/1 "2010-08-10T21:21:21Z")

</div>

Hi,

I have an Electrum100 board from Micromint and it has an SPI ADC (ADC128S052) hooked to the SPI1 with PC4 as CS.

I managed to start the SPI port (bit/clock/master settings and so on). Unfortunately, the CS would not toggle (it’s always low). The SPI\_CLK and MOSI pins look just fine on the scope.

The code that I put together is given below:

```auto
/* user-land driver for external ADC on SPI1 CS2 (PC4)
Board: Electrum100 - Micromint, AT91SAM9G20
*/

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <signal.h>
#include <fcntl.h>
#include <ctype.h>
#include <termios.h>
#include <sys/types.h>
#include <sys/mman.h>

#include "definitions.h"

#define MAP_SIZE 4096UL //4k
#define MAP_MASK (MAP_SIZE - 1)

#define SPI_PCS1(npcs) ((~(1 << npcs) & 0xF) << 16)

typedef unsigned char u08;
typedef signed char s08;
typedef unsigned short u16;
typedef signed short s16;
typedef unsigned long u32;
typedef signed long s32;
typedef unsigned long long u64;
typedef signed long long s64;

int fd, i, repetitions;
void *piob_base, *pioc_base, *spi1_base, *pmc_base, *aic_base;

// found on Atmel website
u16 spi_tx_rx(u32 TxData)
{
unsigned int RxData = 0;

//MASK UNUSED BITS
TxData &= 0x0000FFFF;
TxData|=SPI_PCS1(1)| AT91C_SPI_LASTXFER;
//WAIT UNTIL TRANSMIT REGISTER IS EMPTY
while (!(*((unsigned long *) (spi1_base+(AT91C_SPI1_SR & MAP_MASK))) & AT91C_SPI_TXEMPTY));
// TRANSMIT DATA
*((unsigned long *) (spi1_base+(AT91C_SPI1_TDR & MAP_MASK))) = TxData ;
//READ THE RECEIVED DATA
//WAIT UNTIL RECEIVE REGISTER IS FULL
while (!(*((unsigned long *) (spi1_base+(AT91C_SPI1_SR & MAP_MASK))) & AT91C_SPI_RDRF));
//READ RDR AND MASK UNUSED BITS
RxData = (*((unsigned long *) (spi1_base+(AT91C_SPI1_RDR & MAP_MASK))));

return (RxData&0xffff) ;
}

void open_controller(){

...
...
...

mmap() and error checking ...

}

int main() {

int buf[10000];
i=0;

open_controller();
// PMC setting

*((unsigned long *) (pmc_base+(AT91C_PMC_PCER & MAP_MASK))) = 1<<AT91C_ID_SPI1;

*((unsigned long *) (piob_base + (PIOB_PDR & MAP_MASK))) = AT91C_PB0_SPI1_MISO | AT91C_PB1_SPI1_MOSI | AT91C_PB2_SPI1_SPCK;
*((unsigned long *) (pioc_base + (PIOC_PDR & MAP_MASK))) = AT91C_PC4_SPI1_NPCS2_0;

// peripherals definitions
*((unsigned long *) piob_base + (PIOB_ASR & MAP_MASK)) = AT91C_PB0_SPI1_MISO | AT91C_PB1_SPI1_MOSI | AT91C_PB2_SPI1_SPCK;
*((unsigned long *) pioc_base + (PIOC_BSR & MAP_MASK)) = AT91C_PC4_SPI1_NPCS2_0;

// SPI1 setup

*((unsigned long *) (spi1_base+(AT91C_SPI1_CR & MAP_MASK))) = AT91C_SPI_SPIDIS;
*((unsigned long *) (spi1_base+(AT91C_SPI1_CR & MAP_MASK))) = AT91C_SPI_SWRST ;
*((unsigned long *) (spi1_base+(AT91C_SPI1_CR & MAP_MASK))) = AT91C_SPI_SPIEN | AT91C_SPI_LASTXFER ;
*((unsigned long *) (spi1_base+(AT91C_SPI1_MR & MAP_MASK))) = AT91C_SPI_MSTR | SPI_PCS1(1)|AT91C_SPI_PS_VARIABLE ;
*((unsigned long *) (spi1_base+(AT91C_SPI1_CSR1 & MAP_MASK))) = AT91C_SPI_NCPHA| AT91C_SPI_CPOL | AT91C_SPI_BITS_16 |0x6f<<8 ;

while(i<100000){
usleep(30);
printf("%lu \n",spi_tx_rx(1<<10));

i++;
}

*((unsigned long *) (spi1_base+(AT91C_SPI1_CR & MAP_MASK))) = AT91C_SPI_SPIDIS;

close(fd);
return 0;
}

```

Thanks a lot.

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<div class="post-metadata">

**Author:** ![lnxfrk](https://avatars.discourse-cdn.com/v4/letter/l/ce73a5/32.png) [@lnxfrk](https://community.sparkfun.com/u/lnxfrk)\
**Post date:** [August 11, 2010, 3:00pm UTC](https://community.sparkfun.com/t/spi1-at91sam9g20-external-adc/16925/2 "2010-08-11T15:00:39Z")

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Anybody?

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<div class="post-metadata">

**Author:** ![theatrus](https://avatars.discourse-cdn.com/v4/letter/t/a8b319/32.png) [@theatrus](https://community.sparkfun.com/u/theatrus)\
**Post date:** [August 12, 2010, 10:15pm UTC](https://community.sparkfun.com/t/spi1-at91sam9g20-external-adc/16925/3 "2010-08-12T22:15:13Z")

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All of my 9G20s run Linux 🙂

You can perhaps look at the SPI driver there for ideas.

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<div class="post-metadata">

**Author:** ![lnxfrk](https://avatars.discourse-cdn.com/v4/letter/l/ce73a5/32.png) [@lnxfrk](https://community.sparkfun.com/u/lnxfrk)\
**Post date:** [August 13, 2010, 4:45am UTC](https://community.sparkfun.com/t/spi1-at91sam9g20-external-adc/16925/4 "2010-08-13T04:45:01Z")

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Thanks for answering my post.

No help there. That was the first thing I did.