AS1531

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.

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

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.

Load driver

To use the AS1531, first load as1531 module:

# modprobe as1531

Read channels value

# 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.