ADS1256: Fast read and write

Hi Luc,

You have us at a slight disadvantage here - none of us are familiar with the hardware you have using the ADS1256. Can you perhaps provide a part number for the board you bought or point us to the schematics for it?

I'm currently running this loop(see below). Right now the outer loop which waits for the DRDY to become available runs around 60 times before entering once. If I would be able to decrease the wait time, I could check the ADC input more often then in this case.

Best regards,


int main()
{
uint8_t id;
int32_t adc[8];
int32_t volt[8];
uint8_t i;
//uint8_t ch_num;
int32_t iTemp;
//uint8_t buf[3];
//uint32_t DACVAL;
//uint16_t _D_;
//uint16_t newvar;
uint8_t _ch;
int8_t counter;


if (!bcm2835_init())
return 1;

bcm2835_spi_begin();
bcm2835_spi_setBitOrder(BCM2835_SPI_BIT_ORDER_LSBFIRST ); // The default
bcm2835_spi_setDataMode(BCM2835_SPI_MODE1); // The default
bcm2835_spi_setClockDivider(BCM2835_SPI_CLOCK_DIVIDER_256); // The default
bcm2835_gpio_fsel(SPICS, BCM2835_GPIO_FSEL_OUTP);//
bcm2835_gpio_write(SPICS, HIGH);
bcm2835_gpio_fsel(DRDY, BCM2835_GPIO_FSEL_INPT);
bcm2835_gpio_set_pud(DRDY, BCM2835_GPIO_PUD_UP);
//ADS1256_WriteReg(REG_MUX,0x01);
//ADS1256_WriteReg(REG_ADCON,0x20);
// ADS1256_CfgADC(ADS1256_GAIN_1, ADS1256_15SPS);

//~ struct timespec tstart = {0,0}, tend = {0,0};
//~ clock_gettime(CLOCK_MONOTONIC, &tstart);

//~ clock_gettime(CLOCK_MONOTONIC, &tend);
//~ printf("computation took about %.5f seconds\n",((double)tend.tv_sec + 1.0e-9*tend.tv_nsec) - ((double)tstart.tv_sec + 1.0e-9*tstart.tv_nsec));


id = ADS1256_ReadChipID();
printf("\r\n");
printf("ID=\r\n");

if (id != 3)
{
printf("Error, ASD1256 Chip ID = 0x%d\r\n", (int)id);
}
else
{
printf("Ok, ASD1256 Chip ID = 0x%d\r\n", (int)id);
}
/*
11110000 = 30,000SPS (default)
11100000 = 15,000SPS
11010000 = 7,500SPS
11000000 = 3,750SPS
10110000 = 2,000SPS
10100001 = 1,000SPS
10010010 = 500SPS
10000010 = 100SPS
01110010 = 60SPS
01100011 = 50SPS
01010011 = 30SPS
01000011 = 25SPS
00110011 = 15SPS
00100011 = 10SPS
00010011 = 5SPS
00000011 = 2.5SPS
*/


ADS1256_CfgADC(ADS1256_GAIN_1, ADS1256_1000SPS);
ADS1256_StartScan(0);
g_tADS1256.ScanMode = 0; //channel mode 0 = single, 1 = differential
//ADS1256_SetChannal(0); //channel mode 0 = single, 1 = differential

//ch_num = 8;
i = 2;
counter = 0;


while(1) //outer loop
{
// time sampe outer loop
struct timespec tstart = {0,0}, tend = {0,0};
clock_gettime(CLOCK_MONOTONIC, &tstart);

//Count loop times before entering innerloop
counter = counter +1;
printf("%d counter \r\n",counter);


while (DRDY_IS_LOW()) //inner loop
{
//ADS1256_ISR();
//return 1;

struct timespec tstart = {0,0}, tend = {0,0};
clock_gettime(CLOCK_MONOTONIC, &tstart);

/*running ADS1256_ISR inside loop */
//ADS1256_SetChannal(g_tADS1256.Channel); /*Switch channel mode */
_ch = g_tADS1256.Channel; //instead of ADS1256_SetChannal function

ADS1256_WriteReg(REG_MUX, (_ch << 4) | (1 << 3)); //instead of ADS1256_SetChannal function

bsp_DelayUS(5);

ADS1256_WriteCmd(CMD_SYNC);
bsp_DelayUS(5);

ADS1256_WriteCmd(CMD_WAKEUP);
bsp_DelayUS(5);



if (g_tADS1256.Channel == 0)
{
g_tADS1256.AdcNow[7] = ADS1256_ReadData();
}
else
{
g_tADS1256.AdcNow[g_tADS1256.Channel-1] = ADS1256_ReadData();
}

if (++g_tADS1256.Channel >= 8)
{
g_tADS1256.Channel = 0;
}

printf("%d DRADY low \r\n",DRDY);


adc[i] = ADS1256_GetAdc(i);
volt[i] = (adc[i] * 100) / 167;

printf("%d volt \r\n",volt[i]);

iTemp = volt[i];
printf("%d iTemp \r\n",iTemp);


//~ iTemp = volt[i]; /* uV */
//~ if (iTemp < 0)
//~ {
//~ iTemp = -iTemp;
//~ printf(" (-%ld.%03ld %03ld V) \r\n", iTemp /1000000, (iTemp%1000000)/1000, iTemp%1000);
//~ }
//~ else
//~ {
//~ printf(" ( %ld.%03ld %03ld V) \r\n", iTemp /1000000, (iTemp%1000000)/1000, iTemp%1000);
//~ }

counter = 0;
clock_gettime(CLOCK_MONOTONIC, &tend);
printf("computation innerloop took about %.5f seconds\n",((double)tend.tv_sec + 1.0e-9*tend.tv_nsec) - ((double)tstart.tv_sec + 1.0e-9*tstart.tv_nsec));


} //end DRDY while loop

clock_gettime(CLOCK_MONOTONIC, &tend);
printf("computation outerloop took about %.5f seconds\n",((double)tend.tv_sec + 1.0e-9*tend.tv_nsec) - ((double)tstart.tv_sec + 1.0e-9*tstart.tv_nsec));

} //end while(1) loop

} //end int main