RC Car
Five directions and five speeds — the box is the remote
An IO expander on the board I2C header drives a two-motor car: PCA9685 (16-channel 12-bit PWM) gives proportional speed, while PCF8574 also works but only at fixed speed. Both are auto-detected at boot. On screen there is a cross-shaped D-pad (forward, reverse, left, right, stop) with five speed steps on the right; the console supports timed nudges.
An 800 ms watchdog disables the drivers and coasts the car whenever commands stop arriving, so a dropped link cannot send it running off. Brake mode shorts both motor terminals for a faster stop than coasting.
On-screen interface
A recreation of this page on the 2.41-inch AMOLED display (600 × 450). Actual interaction and layout follow the latest firmware.
Key capabilities
D-pad plus five speeds
20/40/60/80/100% — press and go.
Differential steering
Opposite wheel directions spin in place for a tighter turning circle.
800 ms watchdog
Stops automatically when commands stop arriving.
Two chips supported
PCA9685 for speed, PCF8574 for fixed speed, auto-detected.
Technical specs
Typical scenarios
Desk car
Drive straight from the touchscreen — no remote to hunt for.
Teaching differential drive
See how wheel speed difference maps to turning radius.
Related commands
page 29 Jump to RC Car car fwd|back|left|right [speed] [ms] e.g. car fwd 60 1000 car stop | brake Coast stop / hard brake car speed <n> Set the default speed step car chip auto|pca|pcf Re-detect or force an expander chip car timeout <ms> Adjust the watchdog window
- Motors need their own supply — do not draw them from the board.
- The PCA9685 module VCC must be 3.3 V: at 5 V its pull-ups drag SDA/SCL to 5 V and damage the GPIOs.
- With no expander connected the page shows wiring guidance; commands are recorded without self-test and never crash.