02 SENSORS RS485 IO MIC

TC74 onboard temperature sensor

Run this to get temperature in C°:

cd /sys/class/hwmon/hwmon0

cat temp1_input

Displayed temperature must be divided by 1000.

EEPROM

cd /sys/bus/i2c/devices/2-0050

echo -ne "a" > eeprom #write single byte

cat eeprom # read full eeprom

Last 48bit of eeprom represent an unique EUID.

ADC

cd /sys/bus/iio/devices/iio\:device0

cat in_voltage0_raw #read adc value

grep "" * #read all

while sleep 0.2 ; do cat in_voltage0_raw ; done #read values in loop

Linux	Connector
ADC0	AN0
ADC1	BATTERY MONITOR
ADC2	NTC2
ADC3	NTC1
ADC4	AN_LED
ADC5	AN_AC

GPIO INPUT

cd /sys/class/gpio

ls

To read the gpios, run:

cd /sys/class/gpio

echo 128 > export

echo 129 > export

echo 130 > export

echo 131> export

IN0	128
IN1	129
IN2	130
IN3	131

then you can do:

cd gpio129

cat value #read input value

PWM / DO

cd /sys/class/pwm/pwmchip0

echo 0 > export

echo 2 > export

cd pwm0

echo 1000000 > period #Setting 1Khz

echo 500000 > duty_cycle # 50% Duty cycle

echo 0 > duty_cycle # 100% Duty cycle

echo 1000000 > duty_cycle # 0% Duty cycle

echo 1 > enable

Linux	Schematic
pwm2	OUT1
pwm0	OUT2

If you have some issue and not see any output, try toggling che enable file.

echo 0 > enable

echo 1 > enable

RS485

Serial is on /dev/ttyAMA4 or ttySAC4

Install screen:

apt-get update; apt-get install -y screen

Run:

screen /dev/ttyAMA4

or

echo "hello" > /dev/ttySAC4 #test only send

Only doing 'cat' is not enough if you did not configure the serial.

HOME KEY

Pressing home key is the same as pressing a keyboard button.

cat /dev/input/event0

Accellerometer - LSM6DSL

LSM6DSL is an accellerometer and gyroscope sensor, you will see 2 diffrent devices for each functionality (accel and gyro).

cd iio:device1

cat name #lsm6dsl_accel is returned

cat sampling_frequency_available #list supported sample rate

echo 26 > sampling_frequency #configure 26hz as sample rate

cat in_accel_x_raw #read x axes accelleromer value

For a real application you may require a raw flow of data with low overhead, in that case we will need to use the buffer:

# Enable channels we want to retrieve
echo 1 > scan_elements/in_accel_x_en 
echo 1 > scan_elements/in_accel_y_en 
echo 1 > scan_elements/in_accel_z_en 
echo 1 > scan_elements/in_timestamp_en #nanoseconds timestamp

# Enable buffer
echo 1 > buffer/enable

Now you can read the values from /dev/iio:device2

The format of the data is described in scan_elements/<channel>_type.

To try it out:

dnf install kernel-tools

iio_generic_buffer --device-num 2 -g -c 10

To handle high sample rate you will also require to modify /buffer/length and /buffer/watermark according to your requirements.

# Disable buffer
echo 0 > buffer/enable

Event handling

The drivers embeds also event capabilities (tap, double tap, freefall, pedometer, tilt, wakeup).

On the device folder you can see diffrent events to enable.

Each event may require different sample rate to work correctly:

Event	Sample rate
Tap	416
Double tap	416
Freefall	416
Wakeup	416
Tilt	26
Pedometer	26

#Enable tilt
echo 1 > event_tilt_en

Now rotate the board at 180°

#Pop event buffer
cat event_pop_buffer_dbg #should print tilt,0,<timestamp>

To keep reading events you need to read this virtual file at a fixed rate (like 100ms). If a new event is detect you will receive a string with this format:

<event>,<extra data>,<timestamp>

event can be tap, dtap, step, tilt, freefall, wakeup

extra_data contains only the number of steps performed in case of a step event.

If no event was detected the file reading will throw a -EAGAIN (-11) error.

Actually the I/O standard has a different way to throw events then the one used by this driver, so you won't receive anything on IIO_GET_EVENT_FD_IOCTL. For different reasons we had to do it in another way, but we are working on a solution to align it to the standard.

Gyroscope - LSM6DSL

Works like the accelerometer but it should be on iio:device2

Microphone

To record audio you can run:

arecord -Dmic -r 44000 -f S32_LE prova.wav

The 'mic' plug binds internal filter to audio recording, since the hw codec does not handle high pass filter and amplification, we need to do it at software level with alsa.

You can check the configuration by reading /etc/asound.conf

Note: If you are running the command for the first time on release v1.0, you may need to start a short dummy recording and then increase the volume with alsamixer command up to 75%, then you can run the above command without issues.