AS1531

Introduction

AS1531 is a 12bits 8 channels Analog to Digital Converter made by Austriamicrosystem. Its use a SPI bus to communicate with a master microprocessor. A driver is included in the Armadeus BSP/SDK and can be used on the APF51Dev board.

Connecting chip on APF boards

• On the APF51Dev, the AS1531 is connected to the SPI1 bus by default, so you can move to next chapter.
• On the APF27Dev board it can be soldered on SPI3 bus, which is available 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 linux-menuconfig

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

• Then rebuild the Linux and rootfs images:

$ make linux && 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.

Examples

• Script to read all values each 500ms and display them on console:

#!/bin/sh

modprobe as1531

loop=1
while [ "$loop" == 1 ]; do
        for i in 0 1 2 3 4 5 6 7; do
                value=`cat /sys/bus/spi/devices/spi0.0/in"$i"_input`
                echo -n "$value  "
        done
        usleep 500000   # 500ms
        echo
done