AS1531
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Contents
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.
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