AS1531

Introduction

AS1531 is a 8 channels 12bits analog do digital converter made by Austriamicrosystem. The driver is included in ARMadeus distribution, but not currently on ARMadeus board.

Soldering

AS1531 chip use a SPI bus to communicate with the microprocessor, then to use it on APFx board it must be solder on a SPI bus. For example on APF27-Dev board it can be soldered on SPI3 bus, that can be found on connector J8.

Soldering schema for SPI3 APF27-dev

J8 pin	AS1531 pin
SD1_D0_SPI3_MISO	DOUT
SD1_D3_SPI3_SS	CSN
SD1_CMD_SPI3_MOSI	DIN
SP1_CLK_SPI3_SCLK	SCLK

Driver

The driver is included in ARMadeus distribution, then to use it, select it :

[  ] $ make linux26-menuconfig

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

If the chip is plugged on SPI3 don't forget to select SPI3 and platform module :

Device Drivers  --->
    [*] SPI support  --->
        [*]     CSPI3

Device Drivers  --->
    Armadeus specific drivers  --->
        <M>   AS1531 platform data

Then compile the distribution :

[  ] $ make linux26;make

Use it

modprobe

To use the ADC first load module hwmon and as1531 (if configured as module) :

# modprobe hwmon
# modprobe as1531
# modprobe as1531_plat

read values

If chip is plugged on SPI3, adc input file will be found under directory :

# cd /sys/bus/spi/devices/spi2.0/
# 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.