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AM335x: 4-wire TSC with 4 general-purpose ADC channels

Satyanarayana Reddy
Prodigy 165 points

Hi,

We want to use the All ADC Channels in  "4-wire TSC with 4 general-purpose ADC channels" mode.

Because, we have the 4-Wite Touch SCreen (Interfaced to AIN0, AIN1, AIN2 and AIN3) and 4 no's of Temprature Sensors (NTC Resistors) (Interfaced to AIN4, AIN5, AIN6 and AIN7).

Is the Linux BSP Supports TSC and ADC are working same time?.

If not, Now, How i can program the Linux BSP Drivers to support 4-Wire TSC and another 4-ADC working simultaneusly?.

Is there any standlaone example for using the TSC and ADC's,  to start Linux BSP Driver Modification?.

Thanks

Reddy

  • 0
    Prodigy 165 points

    Hi,

    I had completed the tsc linux driver modifications to work 4-Wire Touch Screen and 4-Channel General Puprpose ADC.

    AIN0, AIN1, AIN2 and AIN3 are used fro Touch Screen, and AIN4, AIN5, AIN6 and AIN7 are used as General Purpose ADC Channels.

    From Platfrom driver data, ADC capture can enabled, and and also ADC Capture period in milli seconds can be mentioned.

    Present driver using the FIFO 0 for ADC Channels and FIFO 1 for TSC. Data capture in Interrupt mode (non-DMA) hence, capture period is limited to above 100ms.

    This can be changed depend on the requirements.

     

    The Patch is attched for refernce.

     

    Thanks

    Reddy8816.0001-TSC-General-Purpose-ADC-capturing-added-to-TSC-Modul.zip

  • 0 in reply to Satyanarayana Reddy
    Intellectual 370 points

    Hey Reddy,

    I wanted to apply your patch but it seems like you are using a different kernel version than me. I get the following:
    patch -p1 --dry-run <0001-TSC-General-Purpose-ADC-capturing-added-to-TSC-Modul.patch

    patching file drivers/input/touchscreen/ti_tscadc.c
    Hunk #3 succeeded at 111 (offset -1 lines).
    Hunk #6 FAILED at 207.
    Hunk #7 succeeded at 292 (offset 30 lines).
    Hunk #8 succeeded at 339 (offset 34 lines).
    Hunk #9 succeeded at 373 (offset 34 lines).
    Hunk #10 succeeded at 402 (offset 34 lines).
    Hunk #11 succeeded at 437 (offset 34 lines).
    Hunk #12 succeeded at 626 with fuzz 2 (offset 34 lines).
    Hunk #13 succeeded at 650 (offset 34 lines).
    Hunk #14 succeeded at 708 (offset 34 lines).
    Hunk #15 FAILED at 698.
    Hunk #16 succeeded at 744 (offset 30 lines).
    Hunk #17 FAILED at 758.
    3 out of 17 hunks FAILED -- saving rejects to file drivers/input/touchscreen/ti_tscadc.c.rej
    patching file include/linux/input/ti_tscadc.h
    Hunk #1 succeeded at 18 with fuzz 2 (offset 9 lines).

    Using standard SDK from TI, your patch does not seem to work. What did you use? Did you apply some other patches before?
    Cheers Sam
  • 0 in reply to Satyanarayana Reddy
    Intellectual 370 points
    Hi Reddy,
    thanks for your reply. But the patch doesn't work for me. I took the latest commit (2011-12-12, Patil, Rachna) and then applied the patch. Still get "6 out of 17 Hunks FAILED".
    Cheers
    Sam
  • 0 in reply to Samuel Egli
    Prodigy 165 points

    Hi Sam,

     

    I had attched the .h and .c files.

     

    Reddy

    6201.ti_tscadc.tar.gz

  • 0 in reply to Satyanarayana Reddy
    Intellectual 370 points
    Thanks! I'll try this out as soon my board works again. Looks like sd-card reader is broke :-(
    Sam
  • 0 in reply to Satyanarayana Reddy
    Intellectual 370 points
    Hi Reddy,
    thanks again the files. I tested it and it worked fine (the evm seems to work again). However, I'm wondering about signals that I measured.
    - All four Channels had a different offset (max/min offset at ~780/300, i.e. channel1= min offset and channel4 = max offset) 
    - And when I used the touch panel I could see the four channels being heavily affected.
    Frankly speaking I would have expected to have a smaller offset on all channels and that the offset would be the same on every channel. 
    But to measure different values when the touch panel is used is quite surprising. Actually a ADC is not useful at all having that much cross talk. 
    Channel 4 is affected the most (max value ~2400).
    I hope I'm measuring something wrong here. Did you observe something similar?
    Sam
  • 0 in reply to Samuel Egli
    Prodigy 165 points

    Hi Sam,

    How General Purpose ADC inputs are interfaced?.

    What is the capacitive load?. In My board, we have the ADC inputs are loaded with Resistive load only.

    I had seen only offset  20 to 30 on each channel, and we had measured the input Voltages and  calculated the same.

    We have to enable the Hardware Preempt for proper working of  Touch Screen, when ADC Capture is going on.

    I had modified the files. Find the updated files.

    Reddy

    0777.ti_tscadc.tar.gz

  • 0 in reply to Satyanarayana Reddy
    Intellectual 370 points
    Hi Reddy,
    thanks again. No, there is no capacitive load. I'm using am335xevm board. I guess I have to dig deeper to understand how it works. I'll check out your update when I've time. 
    Sam 
  • 0 in reply to Satyanarayana Reddy
    Intellectual 715 points

    Reddy,

                Thank you very much for the posted code. It helped me immensely to get to grips with ADC. I have a similar but different LCD screen so the driver is different too but looking at your code I was able to quickly implement the required changes to read the ADC as well.

    I'm going to be trying to improve the sample rate now. Have you made it work with DMA? Have you got some good pointers for that (main gotchas and nuances)? 

    Thanks.

  • 0 in reply to Satyanarayana Reddy
    Prodigy 25 points

    Hi,Reddy

    I don't know how to test the 4-Channel General Puprpose ADC driver,can you tell me ?

    Thanks.

  • 0 in reply to chao liu
    Intellectual 715 points

    If you've successfully compiled and installed the driver then it will be available as a device which you can simply read from-- either by writing a program that opens the device just like a file and reads from or by simply cat-ing the contents of the device like this:

    code example said:

    cat /sys/devices/platform/tsc/channel_1

    Well in your case the path to "channel_1" may be different but that's where I ended up having it.

    What is more interesting, is how to improve the sample rate from 10Hz to a lot higher value and that's something I'm hoping to achieve by using edma. Will update on my progress.