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Tool/software:
Hello,
here is a detailed description of which parts I am using and what my problem is:
I'm using the ADS1278EVM-PDK eval board (An older version from 2011, can be seen on atached photo).
The eval board is also connected to the MMB0 motherboard. The Motherboard is only connected to power and not also to the software via USB, since I want to create a different external communication directly from the eval board.
When setting all the switches and jumpers to SPI mode (in all different configurations) the communication does not seem to work correctly. The main problem seems to be the FSYNC/DRDY pin on the chip itself, as it only stays low or high depending on the configuration and does not act as some sort of SPI chip select as I understand it should from the datasheet. The onboard clock works, as do the Digital out pins that output some data, but without the FSYNC/DRDY pin working as the SPI chip select I do not know how to parse the continous digital data coming out.
It may also be relevant that the board works completely fine in the FS mode and connected via USB to the TI software.
TLDR: I would like to use the eval boad in SPI mode without the motherboard (or only using the power from the motherboard) and connect the output to some other device for digital data reading (for example raspberrypi).
Hello Nik,
Welcome to the TI E2E community.
The ADFS1278EVM-PDK is not easy to interface to a separate controller board, but it can be done.
In order to use standalone, the SPI lines from the MMB0 board must be disconnected from the daughter board, otherwise you will have contention between the MMB0 and your controller board. Other customers have removed the daughter board from the MMB0 board and used wire jumpers between the two boards to provide power only, and then used jumpers for the SPI port between the daughter board (ADS1278EVM) and the controller board. Below is another e2e link where this was successfully done.
With everything correctly powered and configured in SPI mode, with no SPI communications (SCLK idle low), the ADS1278 should be in continuous conversion mode, with the /DRDY line pulsing at the output data rate.
Using the onboard 27MHz oscillator, CLKDIV=1 (connected to IOVDD), MODE Selection = 00 (connected to ground), you should see /DRDY repeating at 105468 sps. On /DRDY falling edge, you should then activate SCLK and read data on the DOUT1 pin. For 8 channels and 24b per channel, you will need to send a total of 192 SCLKs. After reading all channel data, leave SCLK low and wait for the next /DRDY falling edge to read the next conversion result.
In order to read all 8 channels using a single SPI port, you will need to use TDM mode; make sure all FORMAT pins are low (connected to ground) to enable this mode.
The ADS1278EVM can require some trial and error to get everything configured correctly. I suggest using a scope or DMM to verify all configuration pin states, and verify that the 27MHz oscillator is actually connected to the CLK pin of the ADS1278. Once you see the /DRDY working at the correct frequency of 105468 sps, then you can work on getting your code working to transfer the data over the SPI connections. (SCLK, DOUT1, and /DRDY usually connected to an interrupt pin or can be software polled).
Regards,
Keith Nicholas
Precision ADC Applications
