Using I2C ADC#
Using I2C device on BeagleY-AI is similar to using it on any Raspberry Pi compatible board. The image below shows the BeagleY-AI I2C pinout when using 5V for device VCC. For more information check pinout.beagley.ai/pinout/i2c.
![BeagleY-AI I2C pinout (5V)](../../../../_images/i2c-pinout-5v.png)
Fig. 126 BeagleY-AI I2C pinout (5V)#
ADS1115 16-bit ADC#
Wiring/connection#
Following the I2C pinout shown above let’s make the connection of our ADS1115 ADC.
![ADS1115 connection](../../../../_images/ads1115-connection.png)
Fig. 127 ADS1115 connection#
Tip
The ADC can work on 2.0V - 5.5V
voltage range, here we have selected to run it on 5V
from HAT PIN2
. For more information checkout ADS1115 datasheet.
To check if your ADS1115 ADC is correctly connected to your BeagleY-AI you can use i2cdetect
command as shown below.
i2cdetect -y -r 1
The above command should show 48
address occupied in the output, which is the default I2C address of our ADS1115 ADC.
debian@BeagleBone:~$ i2cdetect -y -r 1
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- 48 -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
ADC Parameters#
PGA#
The pga is the programmable gain amplifier (values are full scale), in the device tree overlay we have ti,gain = <#>;
where #
can be following,
0
: +/- 6.144 V1
: +/- 4.096 V (default)2
: +/- 2.048 V3
: +/- 1.024 V4
: +/- 0.512 V5
: +/- 0.256 V
Data rate#
The data_rate in samples per second, in the device tree overlay we have ti,datarate = <#>;
where #
can be following,
0
: 81
: 162
: 323
: 644
: 1285
: 2506
: 4757
: 860 (default)
ADC Inputs#
The inputs can be made available by 8 sysfs input files in0_input - in7_input,
in0
: Voltage over AIN0 and AIN1.in1
: Voltage over AIN0 and AIN3.in2
: Voltage over AIN1 and AIN3.in3
: Voltage over AIN2 and AIN3.in4
: Voltage over AIN0 and GND.in5
: Voltage over AIN1 and GND.in6
: Voltage over AIN2 and GND.in7
: Voltage over AIN3 and GND.
Note
In the device tree overlay we have channel@4 - channel@7
device tree nodes representing in4 - in7
from the list above.
Using kernel driver#
To use the kernel driver to drive the ADS1115 ADC, we have created an overlay /boot/firmware/overlays/k3-am67a-beagley-ai-i2c1-ads1115.dtbo
.
To load the overlay you have to add fdtoverlays /overlays/k3-am67a-beagley-ai-i2c1-ads1115.dtbo
to /boot/firmware/extlinux/extlinux.conf
as shown below.
...
...
...
label microSD (default)
kernel /Image
append console=ttyS2,115200n8 root=/dev/mmcblk1p3 ro rootfstype=ext4 resume=/dev/mmcblk1p2 rootwait net.ifnames=0 quiet
fdtdir /
fdt /ti/k3-am67a-beagley-ai.dtb
fdtoverlays /overlays/k3-am67a-beagley-ai-i2c1-ads1115.dtbo
After rebooting the board you should see /sys/bus/iio/devices/iio:device0
available.
debian@BeagleBone:~$ ls /sys/bus/iio/devices/ | grep iio
iio:device0
To show all the ADC Inputs you can create a script called adcreader.sh
.
Create the file,
nano adcreader.sh
Copy and paste the content below,
in0=$(cat /sys/bus/iio/devices/iio\:device0/in_voltage0-voltage1_raw)
in1=$(cat /sys/bus/iio/devices/iio\:device0/in_voltage0-voltage3_raw)
in2=$(cat /sys/bus/iio/devices/iio\:device0/in_voltage1-voltage3_raw)
in3=$(cat /sys/bus/iio/devices/iio\:device0/in_voltage2-voltage3_raw)
in4=$(cat /sys/bus/iio/devices/iio\:device0/in_voltage0_raw)
in5=$(cat /sys/bus/iio/devices/iio\:device0/in_voltage1_raw)
in6=$(cat /sys/bus/iio/devices/iio\:device0/in_voltage2_raw)
in7=$(cat /sys/bus/iio/devices/iio\:device0/in_voltage3_raw)
echo "in0=${in0}\nin1=${in1}\nin2=${in2}\nin3=${in3}\nin4=${in4}\nin5=${in5}\nin6=${in6}\nin7=${in7}"
To allow the execution of the script as normal user use the command below,
chmod +x adcreader.sh
To view the ADC updates every 100ms use the
watch
command as shown below,
watch -n 0.1 adcreader.sh
The above command should show the values as shown below and it will update them every 0.1s
,
Every 0.1s: adcreader1.sh
in0=0
in1=-2
in2=2
in3=0
in4=4447
in5=4762
in6=4470
in7=4696