Overview of the platform
Joy-It Car is a platform …
PICTURE OF THE SYSTEM
Materials
Lights
There are 4 headlights on the robot. Each headlight is composed of 2 addressable WS2812B RGB LEDs.
The first LED data input is connected to the P0 expansion board of the platform.
The control of that kind of LEDs uses the LEnsE WS2812 library for MBED6.
LEDs are powered up by the battery through a 5V voltage regulator on the expansion board of the platform.
GPIO Expander
The GPIO Expander is a PF574A. Its I2C address is 0x38.
Connections to the different sensors is given in the Joy-It Car manual.
PWM Controller for motors
The PWM controller and motor driver is a PCA9633. Its I2C address is 0x70.
Hardware Reset of the PWM driver
An hardware reset is required before using the PCA9633 driver. To do this reset, the microcontroller must send by the I2C transmission line the 2 bytes {0xA5, 0X5A}.
Initialization of the PWM driver
An initialization phase is required : sending 2 bytes with values {0x00 0x01}, and then 2 other bytes with values {0xE8 0xAA} (procedure found in the micropython library examples given by Joy-It).
PWM Channels
Each motor of the JoyCar platform uses 2 PWM channels of the PCA9633 to be controlled in two directions.
Motor |
PWM Channel |
Reg Address |
|---|---|---|
Right |
PWM0 |
0x02 |
PWM1 |
0x03 |
|
Left |
PWM2 |
0x04 |
PWM3 |
0x05 |
Depending on the direction and the speed, you can affect value as mentionned in the next table (from Joy-It JoyCar documentation) :
RIGHT Motor |
LEFT Motor |
|||
|---|---|---|---|---|
Function |
PWM0 |
PWM1 |
PWM2 |
PWM3 |
Strong Braking |
0 |
0 |
0 |
0 |
Soft Braking |
255 |
255 |
255 |
255 |
Go Forward |
0 |
PWM |
0 |
PWM |
Go Reverse |
PWM |
0 |
PWM |
0 |
Turn Left |
0 |
0 |
0 |
PWM |
US Sensor
US Sensor Trigger is on pin P8 and US Sensor Echo is on pin P12 of the expansion board.
Servomotors
Servo 1 is on pin P1 and Servo 2 is on pin P2 of the expansion board.