ADC overo 2.6.39+

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Using the ADC's

From posts in the mailing list by Steve Sakoman and others

In linux-omap3-2.6.39 and 3.0 and above

The madc driver is now upstream and in the process it moved to the hwmon subsystem. It is now even easier to access using the /sys/class interface:

root@omap3-multi:~# ls /sys/class/hwmon/hwmon1/device/
curr10_input  in11_input  in3_input  in7_input    power
driver          in12_input  in4_input  in8_input    subsystem
hwmon          in15_input  in5_input  in9_input    temp1_input
in0_input     in2_input   in6_input  modalias    uevent


root@omap3-multi:~# cat /sys/class/hwmon/hwmon1/device/temp1_input
56
root@omap3-multi:~# cat /sys/class/hwmon/hwmon1/device/curr10_input
-750

ADC's via a system call

a quick and very nasty way to access them is by a system call

C

system("cat /sys/class/hwmon/hwmon1/device/in7_input");

Python

os.system("cat /sys/class/hwmon/hwmon1/device/in7_input")

Python

import os
import sys
import subprocess
cmd1 = "cat /sys/class/hwmon/hwmon1/device/in7_input"
process = subprocess.Popen(cmd1, stdout=subprocess.PIPE , shell=True)
os.waitpid(process.pid, 0)[1]
udata = process.stdout.read().strip()
print udata     

In console (in interactive mode)

python
Python 2.6.6 (r266:84292, Sep  1 2011, 13:08:10)
[GCC 4.3.3] on linux2
>>> import os
>>> import sys
>>> import subprocess
>>> cmd1 = "cat /sys/class/hwmon/hwmon1/device/in7_input"
>>> process = subprocess.Popen(cmd1, stdout=subprocess.PIPE , shell=True)
>>> os.waitpid(process.pid, 0)[1]
0
>>> udata = process.stdout.read().strip()
>>> print udata
1388
>>>

Using sysfs from c and fopen and fread

A much useful way to access the adc's is using fopen and fread.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
FILE *fp;
int main(void)
{
   char read_value[4];
   char adcVal2[6];
   if (( fp = fopen("/sys/class/hwmon/hwmon1/device/in2_input", "r")) == NULL)
   {
       printf("Can not open hwmon1 \n");
       exit(1);
   }
   rewind(fp);
   fread(&read_value, sizeof(char), 1 , fp);
   strcpy(adcVal2 , read_value);
   fclose(fp);
   printf("\nADC 2 value = %s \n",adcVal2);
   return 0;
}

Building your own kernel

When building your own kernel Make sure your defconfig has CONFIG_TWL4030_MADC and CONFIG_SENSORS_TWL4030_MADC and make sure your rootfs has the module.

Link to kernel docs for Kernel driver twl4030-madc http://www.sakoman.com/cgi-bin/gitweb.cgi?p=linux-omap-2.6.git;a=blob;f=Documentation/hwmon/twl4030-madc-hwmon;h=ef7984317cecb29eca6ef23a30c21d920e66ef31;hb=refs/heads/omap-2.6.39-pm

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