Difference between revisions of "AS1531"

Revision as of 15:14, 7 October 2011

Introduction

AS1531 is a 8 channels 12bits Analog to Digital Converter made by Austriamicrosystem. The driver is included in ARMadeus distribution and can be used with the APF51Dev board.

Soldering

AS1531 chip use a SPI bus to communicate with the microprocessor, then to use it on APFx board it must be connected to a SPI bus.

On the APF51Dev, the AS1531 is connected to the SPI1 bus by default, so you can move to next chapter.

On the APF27-Dev board it can be soldered on SPI3 bus, which is availbale on connector J8.

Driver

Driver is by default included if you choose an APF51 as target.

Otherwise, you can select it that way:

[  ] $ make linux26-menuconfig

Device Drivers  --->
    <M> Hardware Monitoring support  --->
        <M>   Austria Microsystems AS1531 Analog to Digital Converter

Then compile the distribution :

[  ] $ make linux26 && make

Use it

Warning: AS1531 is used with internal reference voltage of 2,5V, so DO NOT TRY to acquire signals with greater voltage range.

modprobe

To use the ADC, first load hwmon and as1531 modules:

# modprobe hwmon
# modprobe as1531

read values

# cd /sys/bus/spi/devices/spi0.0/
# ls
driver     in1_input  in4_input  in7_input  modalias   subsystem
hwmon      in2_input  in5_input  in_max     name       uevent
in0_input  in3_input  in6_input  in_min     power

or:

# cd /sys/class/hwmon/hwmon0/device/
# ls
driver     in1_input  in4_input  in7_input  modalias   subsystem
hwmon      in2_input  in5_input  in_max     name       uevent
in0_input  in3_input  in6_input  in_min     power

To read adc value just «cat» an input :

# cat in5_input 
887

All values read are in milivolts.