ADS8688 SDO incorrect

Hello,

Would you share an oscilloscope shot of the incorrect SDO?  Please also include the digital lines, SCLK, CS, SDI and SDO, and digital communications. this provides a visual check to make sure that what you think the software is doing vs what in actually is doing.

what are you expecting vs what are you getting?

I suggest using a known DC input to compare the expected output vs the device output.

Regards

Cynthia

Hello Cynthia


thanks for the reply.

1. select channel 0

2. set range 0~2.5

3. read range

but the response is 0, i think it should be 5.

The oscilloscope shot is below,

Is there any suggest?

Best regards

It looks like you are not writing to the register correctly

the timing diagram below demonstrates how to write to a register. also notice that the data written to that register will be outputted in that same cycle.

To write to a register, 24SCLK are needed, although only the first 16 are used.

The first 7 bits are the register address. for CHANNEL 0INPUT RANGE, the address is 05h (found in table 9 of the datasheet)

Then bit 8 needs to be set high to write to it.

Lastly, is the actually content of the register, this is described on table 15. for 2.5xVref : 00h

Put that all together: 0000101 1 0000 0000 or 0B00xh

Follow this same process for reading and writing to the register

Hello Cynthia

Thanks for your reply.

It should be useful, i will try it later,

One more question

I did below

1. Power up the device.

2. RESET the device registers by sending command 0x85000000.

3. sending comman MAN_Ch_n 0xC0000000

4.sending command NO_OP 0x00000000

connet 3.3V or GND ,there is not change.

What should I modify?

Best regards

Hello,

You indicated you solved your problem. I have quite the same issue, when sending 0x85000000 I receive 0x0000FFFF. Then sending 0xC0000000 I still receive 0x0000FFFF. Then sending 0x00000000 I still receive 0x0000FFFF, continuously.

I have tried many things and i now suspect my device is burned because I found no solution to my issue.

Anyway, I'm interested by the solution you have found : what do you mean by 16bits word ? Does it refer to the sequence of clock pulses ? Actually I'm sending by bytes and thus there is a small delay between each byte (0.25µs while the SCLK frequency is 6MHz), but the CS line remains low of course.

Thanks for your information,

Joel

Hello, 

Perhaps the original poster will share anything they have found

You may also create a new post from this thread by clicking the Ask a Related Question on the top right

Regards

Hello 

You can try 0x8500 instead of 0x85000000,

0xC000 instead of 0xC0000000,

when reading data ,send 0x00000000.

Hope it may help you.

Best regards

Hello,

Thanks for your quick reply. Made the change, but still the same result :-(

Regards

Joel

Please make a new post describing your issue, and include a scope shot with the digital lines, SCLK, SDI, SDO and CS

If you suspect that the device is now damaged, you can try the "bad" device on a new board to see if the issue follows the device

Also,  you can use a new device on a new board

Regards

Cynthia