AD5668 support in Linux with ARM Cortex-A8

Hi all,

Greetings !!!

I am interfacing EVAL-AD5668SDCZ with TI-AM335x EVAL Board.

I am using Linux-3.12.30.

I have done integration and driver compilation and successfully got sysfs entries also.

i am able to send the data to DAC register.

But the problem is I am not getting proper output voltage at TP4 (or) OUTPUTA.

I am following the below excellent wiki link from ANALOG DEVICES.

AD5064 IIO Quad-Channel DAC Linux Driver [Analog Devices Wiki]

 

I am getting only Maximum 197.2 mv at the output A.

I am using internal_vref = 2500000 , and below are the sysfs values.

 

$ echo 10000 > /sys/bus/iio/devices/iio\:device0/out_voltage0_raw

$ cat /sys/bus/iio/devices/iio\:device0/out_voltage0_raw

10000

$ cat /sys/bus/iio/devices/iio\:device0/out_voltage0_scale

0.038140

U = out_voltage0_raw * out_voltage0_scale = 10000 * 0,038140 mV = 381,14 mV

According to the above wiki link, i have to get 381.14mv  mv, but i am only getting 197.2v.

If I am giving 100 to out_voltage0_raw, I am getting 16 mV.

What could be the problem ? any jumper settings i have to check in  EVAL-AD5668SDCZ

 

could any body help me in this ?

 

Thank in advance.

 

Regards ,

Bhaskar

Parents
  • 0
    •  Analog Employees 
    on Apr 8, 2016 7:51 AM

    Hi Bhaskar,

    I support the AD5668. I'm not a software engineering so the Linux code doesn't mean much to me. There are no links on the evaluation board that apply directly to VoutA (TP4) so a couple of questions/comments...

    1. LK5 should be in position A or removed to disconnect the REF195 external reference if you want to use the internal reference.

    2. Can you verify that the internal reference voltage (2.5V) can be seen on TP1 when it is enabled?

    3. Do you get the same voltage on other channels if you load the same value?

    4. Does removing LK9 to disconnect the ADG738 make any difference?

    The output voltage you should be seeing is 2*Vref(n/65536) where n is the 16-bit code loaded.

Reply
  • 0
    •  Analog Employees 
    on Apr 8, 2016 7:51 AM

    Hi Bhaskar,

    I support the AD5668. I'm not a software engineering so the Linux code doesn't mean much to me. There are no links on the evaluation board that apply directly to VoutA (TP4) so a couple of questions/comments...

    1. LK5 should be in position A or removed to disconnect the REF195 external reference if you want to use the internal reference.

    2. Can you verify that the internal reference voltage (2.5V) can be seen on TP1 when it is enabled?

    3. Do you get the same voltage on other channels if you load the same value?

    4. Does removing LK9 to disconnect the ADG738 make any difference?

    The output voltage you should be seeing is 2*Vref(n/65536) where n is the 16-bit code loaded.

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