Problem with SPI data transfer with 2 channels (ADC peripheral)

RE: Problem with SPI data transfer with 2 channels (ADC peripheral)

noob_with_ucontrollers — Thu, 30 May 2019 00:05:08 GMT

So I put my ADC (ads1220 from TI) into Continuous Conversion Mode from single shot mode (I was using this mode before), and that enabled me to configure (write to ADC ) in real time.

So yes, it's a timing issue. Just in case anyone else ever needs it. Thank you everyone.

RE: Problem with SPI data transfer with 2 channels (ADC peripheral)

noob_with_ucontrollers — Wed, 29 May 2019 22:53:13 GMT

I will look more into that. Thank you.

Has anyone ever tried initializing and using two SPI instances in one program to get data from two initialized SPIs in the same program? (both instances have separate spi_evt_handlers etc )

RE: Problem with SPI data transfer with 2 channels (ADC peripheral)

awneil — Wed, 29 May 2019 22:16:20 GMT

Could it be a timing issue?

Have you looked at the signals with a scope or analyser, and compared the "working" and "non-working" cases?

And, as already suggested, have you checked with the manufacturer (TI?) whether this is the best way to be using their device? It sounds a little odd to be completely re-initialising just to use a different channel ...

RE: Problem with SPI data transfer with 2 channels (ADC peripheral)

noob_with_ucontrollers — Wed, 29 May 2019 22:04:18 GMT

hmolesworth Yes you are correct. I did fix this. Thank you for your response.

However the problem does not seem to be with the way I am configuring/writing to ADC for initialization. When I configure ADC regs outside the main for () loop, the ADC data is fine and everything works great.

When I paste the exact configuration/initializing code in the main for() loop to re-config my ADC continuously , that's when I stop getting proper data from the ADC.

What would you suggest I do in that case?

RE: Problem with SPI data transfer with 2 channels (ADC peripheral)

hmolesworth — Wed, 29 May 2019 15:14:26 GMT

I think the write command above is incorrect; the first byte requires write command 0x40 (as you have) but also the starting register and number of registers-1. 0x40 only writes 1 register to starting register address 0.

8.5.3.6 WREG (0100 rrnn)
The WREG command writes the number of bytes specified by nn (number of bytes to be written – 1) to the device configuration register, starting at register address rr. The command is completed after nn + 1 bytes are clocked in after the WREG command byte. For example, the command to write two bytes (nn = 01) starting at configuration register 0 (rr = 00) is 0100 0001. The configuration registers are updated on the last SCLK falling edge.

I haven't checked your intended register values, but to write to 4 registers from Register 0 change the first byte to 0x43:

    // Reg hex settings 
    m_tx_buf[0] = 0x40 | 0x00 | (4-1); // Write to register 0 for 4 registers
    m_tx_buf[1] = 0x82;
    m_tx_buf[2] = 0x10;
    m_tx_buf[3] = 0x06; 
    m_tx_buf[4] = 0x20;

RE: Problem with SPI data transfer with 2 channels (ADC peripheral)

Jørgen Holmefjord — Wed, 29 May 2019 13:57:51 GMT

Hi,

If the external ADC does not output correct data, you should check the timings in the datasheet or check with the manufacturer of the device how you should control it correctly. You have checked that the commands are output from the nRF?

Best regards,
Jørgen