Kart/serial link

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Serial link protocol

This section defines the serial link protocol used to communicate between the Kart and the SmartPhone. All data is spontaneous send and can not be polled.

Serial port

Communication is done with:

  • 115200 baud
  • 8 bits
  • no parity
  • no handshake

Message Format

SoF (1 byte) Address (1 byte) Data (2 bytes) EoF (1 byte)
0x55 UINT8 UINT16/INT16 0xAA


SmartPhone to Kart

Address Datatype Description
0 UINT16 DC motor PWM period
1 INT5 DC motor speed: -15 to 15 (Negative numbers = backwards)
2 UINT16 Stepper motor period (speed proportional to 1/period)
3 UINT16 Desired steering angle
4 UINT5 End switch address
5 UINT5 Hardware control
15 UINT16 Serial link update interval [ms]

Hardware control

Bit Meaning Description
0 Kart goes as DC motor When '0', the kart goes backwards when the motor turns forwards
1 Kart turns right (clockwise) When '1', kart turns to the right as stepper motor phases go from 1 to 4
2 End sensor is on left side If '1', the angles are measured clockwise
3 Stepper end emulates an end switch contact for the direction motor
4 Restart Puts following slaves back in startup mode: stepper motor
5 Bluetooth connected Indicates that the Bluetooth connection is established

The end sensor always defines position 0. Angles are always positive.

If bits 1 and 2 are different, the stepper motor phase sequence has to be inverted.

If the Bluetooth connection is lost, the DC motor has to be stopped.

Kart to SmartPhone

Address Datatype Description
0 UINT16 Hall speed count 1
1 UINT16 Hall speed count 2
2 UINT1 Steering status: 0x01 means angle reached
3 UINT16 Actual Steering Angle
4 UINT1 Stepper End (bit is '0' when end switch is pressed)
5 UINT16 ADC Value of the Battery Voltage Level
6 UINT16 Distance
8 UINT16 Proximity 1
9 UINT16 Proximity 2
10 UINT16 Proximity 3
11 UINT16 Proximity 4
12 UINT16 Ambient Light 1
13 UINT16 Ambient Light 2
14 UINT16 Ambient Light 3
15 UINT16 Ambient Light 4
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