This page provides instructions how to customise the alphabot so that it's actually usable for research and it provides a C++ API with proper setters and callbacks.
C++ class to control the basic functionality of a customised Alphabot (https://www.waveshare.com/wiki/AlphaBot) with a Raspberry PI:
- Motor control (using the Parallax Continuous Rotation Servo)
- Battery voltage
Throw the original DC motors in the bin and fit the Parallax Continuous Rotation Servo with 90deg brackets. Plug them into the servo ports S1 and S2.
Wire up the pin header:
GPIO18 / PWM2 = S1 = Motor left
GPIO19 / PWM3 = S2 = Motor right
De-solder the LM2596 and throw it in the bin. It supposed to have a dropout voltage of 1V so that the 7-7.2V from the battery should be fine but it seems to be more 2V. It's not even recommended by TI who recommend the LMR33630 for new designs.
Replace the LM2596 with a MGS100505. Just glue it upside down on the PCB and run 4 wires to Vin and +5V.
Add to /boot/firmware/config.txt:
dtoverlay=pwm-2chan
and reboot.
Check with:
pinctrl -p
that you see:
12: a3 pd | lo // GPIO18 = PWM0_CHAN2
35: a3 pd | lo // GPIO19 = PWM0_CHAN3
which corresponds to the sysfs files:
/sys/class/pwm/pwmchip0/pwm2: GPIO18
/sys/class/pwm/pwmchip0/pwm3: GPIO19
The GPIO pins are accessed via the C++ API of the libgpiod:
apt-get install libgpiod-dev
The demo programs below display the sensor readings with the ncurses library. Install it with
apt-get install libncurses-dev
The built system is cmake. Just type:
cmake .
make
sudo make install
The online documentation is here: https://berndporr.github.io/alphabot/
Start the callback reporting the battery voltage.
start()
Stop the callback.
stop()
Setting the speeds of the left/right wheels:
setLeftWheelSpeed(float speed);
setRightWheelSpeed(float speed);
where speed is between -1 and +1.
There is a callback which reports the battery voltage.
testIO is a simple test program which displays the battery voltage and you can test the motors. It also shows
how the callback is used to display the battery voltage.
testMotor ramps up the motor speed and back again.