ADC FIFO overrun!

Turns out that I set FIFO0Threshold to 64, which is the size of FIFO0. So after I set it to 56, continuous sampling works OK.

But it is wired, since when I set FIFO0THRES to 64, I can get FIFO0COUNT larger than 64, what happened? Does that mean if I only enable one FIFO, it is going to take both FIFO0 and FIFO1. 

Please can somebody tell me what is ADC subsystem's behavior when there is a FIFO overrun? Will it stop AD convert or keep running? I can not find any description about it in the documents.

Hi Guoqiang Xia,

Are you accessing the ADC on Linux platform? If so how you could get the ADC access. I am having trouble in finding any documentation on how to access the ADCs from application.

Some places blog says it can be accessed through ti_tscadc driver. But not much clear information.

Could you please help me on this.

Thanks,

Raja.

koen's blog show how to read adc in shell.

In C you can do this, this read one AD conversion in, you can let it do more, but keep in mind, currently, ti_tscadc only do one shot sampling. You can read ti_tscadc.c to find that out.

int main(int, char**){

int count;

int value[100];

int fadc=open("/sys/devices/platform/tsc/ain0","O_RDONLY);

count=read(fadc, (void *)value,2);

/*then do your thing!*/

close(fadc);

return 0;

}

Hi Guoqiang Xia,

Thanks for posting the sample. I have added the patches to my kernel and followed koen's blog and run the command line arguments. I got Digital inputs. Need to validate the same.

Do we have to configure the step size for ADC?

I could see AIN numbers from 1 - 8, even the patch says channel numbers from 1 - 8 and I think internally driver removes the offset.

Still I have not run the ADC continuously to see FIFO overrun problems.

Regards,

Raja.

Hi Guoqiang Xia,

I could get the ADC values after following the koen's blog.

But While accessing the same port from C sample provided by you, i am getting the read error and errno is EBUSY.

Value updated by read call will be an integer or string. how many bytes we need to read to get proper value.

I have followed your code mentioned above. I am reading ADC pin 1 as AIN2(equivalent to AIN1) as the ti_tscadc driver removes the offset 1 inside.

fadc=open("/sys/devices/platform/tsc/ain2","O_RDONLY);

count=read(fadc, (void *)value,2);

Requesting your help in getting the value.

Thanks,

Raja.

Raja,

  Are you working with ti_tscadc too?

  I edited ti_tscadc.c so it is not the same as the original one.

  I can share the code, but the style and structure of the code is not as good as it should be, also I did not follow a lot of conventions about device drivers, so I am not sure about posting it here, right now its quality is still poor.

  But I think you should work with ti_tscadc to get going, also do not put too much trust on my code sample because it might not work in your case.

Best,

Guoqiang

Hi Guoqiang Xia,

Yes. I am also working on ti_tscadc.

Could you please share me teh ti_tscadc.c code on my email id if you are comfortable. I wont mind about the conventions.

Today morning I could figure it out that the ADC value received from read call is in the form of ascii chars. I missed that point. converting string to integer gives the value equivalent same as getting from command prompt.

Appreciate the help you have provided.

Thanks,

Raja.

Raja,

  Yes, I will send my updated ti_tscadc to your email, but I have to warn you it is just for reference, I am sure there is bug in the driver because I am reading LDD3 while working on the driver, so ...

   Please let me know how I can send it to you.

Best,

Guoqiang