TM4C and ADS1256

Hello Daniel,

The first thing is that during a SSIDataPut for the Transmit, ensure that the SSIDataGet is called to flush out the data, so that when RX operation is being done, the SSIDataGet returns the FIFO data with the actual RX from the Slave. Also the flushing operation must be performed before a transaction: Makes it cleaner.

Regards
Amit

Thanks for your help.
Unfortunately it did not work yet. I still get random numbers and nowhere a the 192(0xC0) I'd like to write to DREG
I did not get your comment about flushing before transaction


Here my updated code

int i;

GPIOPinWrite(GPIO_PORTA_BASE, GPIO_PIN_0, GPIO_PIN_0);//CSLens up
for(i=0;i<1000;i++);
GPIOPinWrite(GPIO_PORTA_BASE, GPIO_PIN_0, 0);//CSLens down

//Empty Input buffer
uint32_t data[2];
while(SSIDataGetNonBlocking(SSI0_BASE, &data[0])){}
for(i=0; i<200;i++);


//WREG DRATE
SSIDataPut(SSI0_BASE, 0x53);
while(SSIBusy(SSI0_BASE))
{
}
SSIDataGet(SSI0_BASE, &data[0]);
for(i=0; i<100;i++);

SSIDataPut(SSI0_BASE, 0x00);
while(SSIBusy(SSI0_BASE))
{
}
SSIDataGet(SSI0_BASE, &data[0]);
for(i=0; i<100;i++);

SSIDataPut(SSI0_BASE, 0xC0);
while(SSIBusy(SSI0_BASE))
{
}
SSIDataGet(SSI0_BASE, &data[0]);
for(i=0; i<100;i++);

//WREG MUX
SSIDataPut(SSI0_BASE, 0x51);
while(SSIBusy(SSI0_BASE))
{
}
SSIDataGet(SSI0_BASE, &data[0]);
for(i=0; i<100;i++);

SSIDataPut(SSI0_BASE, 0x00);
while(SSIBusy(SSI0_BASE))
{
}
SSIDataGet(SSI0_BASE, &data[0]);
for(i=0; i<100;i++);

SSIDataPut(SSI0_BASE, 0x01);
while(SSIBusy(SSI0_BASE))
{
}
SSIDataGet(SSI0_BASE, &data[0]);
for(i=0; i<200;i++);


//RREG DRATE
SSIDataPut(SSI0_BASE, 0x13);
while(SSIBusy(SSI0_BASE))
{
}
SSIDataGet(SSI0_BASE, &data[0]);
for(i=0; i<100;i++);


SSIDataPut(SSI0_BASE, 0x00);
while(SSIBusy(SSI0_BASE))
{
}
//wait 12.5us min 6us
SSIDataGet(SSI0_BASE, &data[0]);
for(i=0; i<100;i++);

SSIDataPut(SSI0_BASE, 0x00);
while(SSIBusy(SSI0_BASE))
{
}
//wait 12.5us min 6us
SSIDataGet(SSI0_BASE, &data[1]);
for(i=0; i<100;i++);

GPIOPinWrite(GPIO_PORTA_BASE, GPIO_PIN_0, GPIO_PIN_0);//CSLens up

Hello Daniel,

Can you please share the SSI configuration code and the GPIO configuration code. As from the post I see that you have PA0 connected from the TM4C device as CS for the ADS. Is that correct?

Regards
Amit

Yes that is correct we have 4 SPI devices on our chip
Here also the smaller code for SPI:

int i;
GPIOPinWrite(GPIO_PORTA_BASE, GPIO_PIN_0, GPIO_PIN_0);//CSLens up
for(i=0;i<1000;i++);
GPIOPinWrite(GPIO_PORTA_BASE, GPIO_PIN_0, 0);//CSLens down

//WREG DRAT
SSIDataPut(SSI0_BASE, 0x53);while(SSIBusy(SSI0_BASE));
for(i=0; i<100;i++);
SSIDataPut(SSI0_BASE, 0x00);while(SSIBusy(SSI0_BASE));
for(i=0; i<100;i++);
SSIDataPut(SSI0_BASE, 0xC0);while(SSIBusy(SSI0_BASE));
for(i=0; i<100;i++);

//WREG MUX
SSIDataPut(SSI0_BASE, 0x51);while(SSIBusy(SSI0_BASE));
for(i=0; i<100;i++);
SSIDataPut(SSI0_BASE, 0x00);while(SSIBusy(SSI0_BASE));
for(i=0; i<100;i++);
SSIDataPut(SSI0_BASE, 0x01);while(SSIBusy(SSI0_BASE));
for(i=0; i<100;i++);


//Empty Input buffer
uint32_t data[3];
while(SSIDataGetNonBlocking(SSI0_BASE, &data[0]));
for(i=0; i<200;i++);


//RREG DRATE
SSIDataPut(SSI0_BASE, 0x13);while(SSIBusy(SSI0_BASE));
for(i=0; i<100;i++);
SSIDataPut(SSI0_BASE, 0x00);while(SSIBusy(SSI0_BASE));
for(i=0; i<200;i++);

SSIDataGet(SSI0_BASE, &data[0]);
SSIDataGet(SSI0_BASE, &data[1]);
SSIDataPut(SSI0_BASE, 0xFF);while(SSIBusy(SSI0_BASE));
SSIDataGet(SSI0_BASE, &data[2]);
for(i=0; i<100;i++);

GPIOPinWrite(GPIO_PORTA_BASE, GPIO_PIN_0, GPIO_PIN_0);//CSLens up


Here the code for SPI configuration:


SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOA);
/* SPI0 */
SysCtlPeripheralEnable(SYSCTL_PERIPH_SSI0);


GPIOPinConfigure(GPIO_PA2_SSI0CLK);
//GPIOPinConfigure(GPIO_PA3_SSI0FSS); //CS done by hand
GPIOPinConfigure(GPIO_PA4_SSI0RX);
GPIOPinConfigure(GPIO_PA5_SSI0TX);

GPIOPinTypeGPIOOutput(GPIO_PORTA_BASE,GPIO_PIN_3);//Set CS for chip one
GPIOPinWrite(GPIO_PORTA_BASE, GPIO_PIN_3, GPIO_PIN_3);//CS up

GPIOPinTypeGPIOOutput(GPIO_PORTA_BASE,GPIO_PIN_6); //Set CS for chip two
GPIOPinWrite(GPIO_PORTA_BASE, GPIO_PIN_6, GPIO_PIN_6); //CSLED up

GPIOPinTypeGPIOOutput(GPIO_PORTA_BASE, GPIO_PIN_1); //set CS for ADS1146
GPIOPinWrite(GPIO_PORTA_BASE, GPIO_PIN_1, GPIO_PIN_1); //CSADS up

GPIOPinTypeGPIOOutput(GPIO_PORTA_BASE, GPIO_PIN_0); //set CS for ADS1256
GPIOPinWrite(GPIO_PORTA_BASE, GPIO_PIN_0, GPIO_PIN_0); //CSADS up

GPIOPinTypeSSI(GPIO_PORTA_BASE, GPIO_PIN_2 | GPIO_PIN_4 | GPIO_PIN_5); // Do not include CS pin 3 (FSS)

SSIConfigSetExpClk(SSI0_BASE, SysCtlClockGet(), SSI_FRF_MOTO_MODE_0, SSI_MODE_MASTER, 500000, 8);
SSIEnable(SSI0_BASE);

B134_332_initDMA();
SPI_init();

Amit Ashara said:

2. Secondly between the operations, the CS must be deasserted.

Yes it's true the CS works in inverted logic, hence the bar over it in the datasheet.

If you only want 1 slave you can simply use a pull-down. In the table "TIMING CHARACTERISTICS FOR FIGURE 1"  it says that on note 3

Dear Amit,

Thanks a lot that helped. The chip is now up and running.

1.) We are also using ADS1146 where we need to work with SSI_FRF_MOTO_MODE_0.

Do you know the correct way to change this mode between each readout on the fly?

2.) The deasserting of the CS was necessary even though it states that this pin can be set to GND.

Hello Daniel,

Yes, it can be done. However before changing the mode please do use SSIDisable to disable the SSI controller

Regards
Amit

While it's true that it, "Can be done" - it's useful often to ask, "Is it wise to do?"  Our experience - most often - NO!

ARM MCUs are famed for having multiple instantiations of peripherals - using a 2nd SPI port would enable your far simpler, "Set-up once & forget!"

Too often we've seen clients employ this "kitchen sink" (i.e. time division multiplex) of a peripheral - and undergo intense "pain/suffering" for their efforts.  (should either of your SPI slaves "demand" quick service - and they're "off-line" (due to the other being currently selected) time muxing fails, most always...)

KISS argues for one peripheral "attaching" to one accessory - at least until the application becomes well known - and time bounded...