Havig trouble with SPI in PIC24FJ256GB412 - c

Question

I am trying to configure a PIC24FJ256GB412 to use the SPI interface with an ADC module(ADS114S08). And now, I can view data by oscilloscope(by measuring the SDI pin). But the SPI1BUFL didn't receive correct data(always received 0x01). Below is the relevant code that I am using to configure the SPI.
uint8_t DATA_S[1000]; // SPI data buffer for Receiving
uint8_t DATA1; // SPI data buffer for Receiving
uint16_t DATA_counter=0;
void System_Initial(void)
{
//Setup IO
TRISDbits.TRISD0 = 0; //SCLK
TRISDbits.TRISD5 = 0; //ADC RESET
TRISDbits.TRISD10 = 0; //ADC START
TRISDbits.TRISD11 = 1; //ADC DRDY
TRISFbits.TRISF3 = 1; //SDI
TRISFbits.TRISF4 = 0; //SDO
ANSELDbits.ANSELD0 = 0; //Digital pins
ANSELDbits.ANSELD5 = 0;
ANSELDbits.ANSELD10 = 0;
ANSELDbits.ANSELD11 = 0;
ANSELFbits.ANSELF3 = 0;
ANSELFbits.ANSELF4 = 0;
//Setup SPI
//MCU operates in 16MHz, ADC internal clk 4MHz
SPI1BRGL = 1; //Baud rate = 4MHz
SPI1CON1L = 0x8020; //8bit mode //SCLK enable //Master Mode
SPI1CON1H = 0x2000; //AUDEN=0
SPI1CON2L = 0x0007; //8bit data
//Setup PPS
__builtin_write_OSCCONL(OSCCON & 0xBF);
_RP11R = _RPOUT_SCK1OUT; // RP11 -> SCK1.
RPINR20bits.SDI1R = 16; // RP16 -> SDI1.
_RP10R = _RPOUT_SDO1; // RP10 -> SDO1.
__builtin_write_OSCCONL(OSCCON | 0x40);
}
//SPI1 - Set ADS114S08
void SPI1_SetADC()
{
//set PGA
//Input MUX Register, address = 02h
//Gain setting Register, address = 03h
SPI1BUFL = 0x42; //WREG at 02h
while( SPI1STATLbits.SPIBUSY==1);
SPI1BUFL = 0x01; //Two bytes
while( SPI1STATLbits.SPIBUSY==1);
SPI1BUFL = 0x01; //02h //AINP = AIN0, AINN = AIN1
while( SPI1STATLbits.SPIBUSY==1);
SPI1BUFL = 0x0B; //03h //PGA enabled, Gain = 011 =8
while( SPI1STATLbits.SPIBUSY==1);
//set Mode
//Data Rate Register, address = 04h
//Reference Control Register, address = 05h
SPI1BUFL = 0x44; //WREG at 04h
while( SPI1STATLbits.SPIBUSY==1);
SPI1BUFL = 0x01; //Two bytes
while( SPI1STATLbits.SPIBUSY==1);
SPI1BUFL = 0x14; //04h //Continuous conversion mode //0100 : 20 SPS
while( SPI1STATLbits.SPIBUSY==1);
SPI1BUFL = 0x30; //05h
while( SPI1STATLbits.SPIBUSY==1);
//set Excitation Current Sources
//Excitation Current Register1(IDACMAG), address = 06h
//Excitation Current Register2(IDACMUX), address = 07h
SPI1BUFL = 0x46; //WREG at 06h
while( SPI1STATLbits.SPIBUSY==1);
SPI1BUFL = 0x01; //Two bytes
while( SPI1STATLbits.SPIBUSY==1);
SPI1BUFL = 0x05; //06h //IDAC = 0101 = 500uA
while( SPI1STATLbits.SPIBUSY==1);
SPI1BUFL = 0xF0; //07h //use IDAC1 => AIN0
while( SPI1STATLbits.SPIBUSY==1);
}
//SPI1 - RREG
void SPI1_RREG()
{
SPI1BUFL = 0x20; //send RREG Command //read 00h
while( SPI1STATLbits.SPIBUSY==1);
SPI1BUFL = 0x00; //1 byte
while( SPI1STATLbits.SPIBUSY==1);
SPI1BUFL = 0x0000; //send DUMMY data
while( SPI1STATLbits.SPIBUSY==1); //Wait Data
uint8_t register1= SPI1BUFL; //get data
DATA1 = register1;
DATA_S[DATA_counter%1000] = register1;
}
int main(void)
{
System_Initial();
LATDbits.LATD10 = 0; //ADC START=0
LATDbits.LATD5 = 0; //ADC RESET=0 //Enter RESET Status
uint32_t loop = 0;
loop = 4*4; //MCU 16Mhz, ADC internal clk 4Mhz
while (loop--); //wait 4clk => ADS114S08 tw(RSL)
LATDbits.LATD5 = 1; //ADC RESET low -> high //Enter Standby Mode
loop=4096*4;
while (loop--); //wait 4096clk => ADS114S08 td(RSSC)
SPI1_SetADC(); //set ADC Configuration
LATDbits.LATD10 = 1; //START high -> Start Conversion
//main while
while(1)
{
DATA_counter++;
SPI1_RREG();
}
}
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As mentioned above, I can see data on SDI pin by oscilloscope.
enter image description here
And another data test.
enter image description here
By the waveform that we can see on the oscilloscope. The ADC module probably works the right way.
But... Let's see the MPLAB IDE side.
enter image description here
I can't get the right data(SPI1BUF = 0x0001). I have tried changing baudrate lower. But the result is no different. Is there a parameter I'm missing? Thanks for your help.
------------------------------------------0530-----------------------------------------------
Hi Craig, I have tried the code.
SPI1BUFL = 0x20; //send RREG Command //read 00h
while(SPI1STATLbits.SPITBF); // wait until the transmit buffer is empty
SPI1BUFL = 0x00; //set 1 byte
while(SPI1STATLbits.SPITBF); // wait until the transmit buffer is empty
uint8_t register1=0;
SPI1BUFL = 0x00; //send DUMMY data
while(!SPI1STATLbits.SPIRBF); //hang until data is received
register1 = SPI1BUFL; //get data
The results were no difference. And I recorded it.
Oscilloscope:
enter image description here
IDE:
enter image description here
enter image description here

Answer 1

The SPI should clear SPI1BUFL every time as you transmit data.
So I try the code like this.
uint8_t SPI_EXCH(uint8_t data)
{
SPI1BUFL = data; // write to buffer for TX
while(!SPI1STATLbits.SPIRBF); // wait for transfer to complete
return SPI1BUFL; // read the received value
}
And every time you try to do an SPI exchange, use the function above.