ADS 8345 interface with LM3s6965 Help!

hercules moreira

Other Parts Discussed in Thread: ADS8344EVM

Hello! I'm working with 2 channels of the ADC8345EVM (16bits ) and when I show the channel 1 value on OLED display it´s change with channel 0.

The other question is that the value show it's wrong. (0V=57680 and 5V=25312)

What's wrong?

Thanks for help!

Look the code beelow;

//**********************************************************************************************************************************************

void config_adc_ssi(unsigned long ulFrequency)
{
SysCtlPeripheralEnable(SYSCTL_PERIPH_SSI0);
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOA);
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOD);
SSIDisable(SSI0_BASE);
GPIOPinTypeSSI(GPIO_PORTA_BASE, GPIO_PIN_2 | GPIO_PIN_5 | GPIO_PIN_4 |GPIO_PIN_3);
GPIOPadConfigSet(GPIO_PORTA_BASE, GPIO_PIN_2 | GPIO_PIN_5 | GPIO_PIN_4 | GPIO_PIN_3,
GPIO_STRENGTH_8MA, GPIO_PIN_TYPE_STD_WPU);
SSIConfigSetExpClk(SSI0_BASE, SysCtlClockGet(),SSI_FRF_MOTO_MODE_3 , SSI_MODE_MASTER,1000000, 16);
GPIOPinTypeGPIOOutput(GPIO_PORTD_BASE, GPIO_PIN_6);
GPIOPadConfigSet(GPIO_PORTD_BASE, GPIO_PIN_6, GPIO_STRENGTH_8MA, GPIO_PIN_TYPE_STD_WPU);
SSIEnable(SSI0_BASE);
}

void start_read_adc(unsigned long channel)
{
SSIDisable(SSI0_BASE);
GPIOPinTypeSSI(GPIO_PORTA_BASE, GPIO_PIN_2 | GPIO_PIN_5 | GPIO_PIN_4 |GPIO_PIN_3);
SSIConfigSetExpClk(SSI0_BASE, SysCtlClockGet(),SSI_FRF_MOTO_MODE_3 , SSI_MODE_MASTER,1000000, 16);
GPIOPinWrite(GPIO_PORTD_BASE, GPIO_PIN_6, 0);
SSIEnable(SSI0_BASE);
SSIDataPut(SSI0_BASE,channel);
while(SSIBusy(SSI0_BASE))
{
}
}
void stop_read_adc(void)
{
unsigned long ulTemp;
GPIOPinWrite(GPIO_PORTD_BASE, GPIO_PIN_6, GPIO_PIN_6);
while(SSIDataGetNonBlocking(SSI0_BASE, &ulTemp) != 0)
{
}
}

int
main(void)
{
SysCtlClockSet(SYSCTL_SYSDIV_1 | SYSCTL_USE_OSC | SYSCTL_OSC_MAIN | SYSCTL_XTAL_8MHZ);
RIT128x96x4Init(1000000);
config_adc_ssi(1000000);
while(1)
{
   // read channel 0 and show on OLED display
   start_read_adc(0x87);
   SSIDataGetNonBlocking(SSI0_BASE, &read_value);
   stop_read_adc();
   RIT128x96x4Enable(1000000);
   usprintf(szBuffer,"%010d",read_value);
   RIT128x96x4StringDraw(szBuffer,40, 24, 15);
   RIT128x96x4StringDraw("Ch_0:", 1, 24, 15);
   usprintf(szBuffer,"%010d",0);
   RIT128x96x4Disable();
   SysCtlDelay(1000);
   // read channel 1 and show on OLED display
   start_read_adc(0xC7);
   SSIDataGetNonBlocking(SSI0_BASE, &read_value);
   stop_read_adc();
   RIT128x96x4Enable(1000000);
   usprintf(szBuffer,"%010d",read_value);
   RIT128x96x4StringDraw(szBuffer,40, 33, 15);
   RIT128x96x4StringDraw("Ch_1:", 1, 33, 15);
   usprintf(szBuffer,"%010d",0);
   RIT128x96x4Disable();
   SysCtlDelay(1000);
   }//while
}//main

//**********************************************************************************************************************************************

over 12 years ago

0 Rafael Ordonez over 12 years ago

TI__Expert 6925 points

Hello Hercules,

Issues related to ADCs wrong readings are very difficult to identify from code alone because they could be related to hardware setup, supplies, digital signal timing, etc.

Thus, to better understand the issue, could you send us the system schematic and scope screenshots of /CS, DIN, DOUT, and SCLK?

For privacy, the schematic can send by a conversation. To start a conversation, go to my profile and click “Start a conversation”.

Thank you.
Rafael

0 hercules moreira over 12 years ago in reply to Rafael Ordonez

Prodigy 20 points

Thanks for the reply!

Don't worry about it! I'm using the Evaluation Module EK-LM3S6965 and ADS8344EVM. I nedded connect some cables, they are; CS, DIN, DOUT, CLK, and GND. It's easy! The configuration of ADC hardware is like this;

W1 2-3

W2 Open

W3 1-2 (+5v)

W4 2-3 (GND)

W5 2-3 (External Reference=5V)

W6 1-2 (NC)

W7 2-3

W8 1-2 ( Chip select by software)

____________________________________

All connections are ok!

I can take some pictures, than I send to you. If you need! I have four channels oscilloscope, I think interesting to you check the signals.

By the way, I'm sorry, my inghish is not very well, I'm from Brazil and I'm learning yet.

Thank you Rafael.

Hercules Vidal

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ADS 8345 interface with LM3s6965 Help!