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
|
Registers
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 orientation
|
6
|
UINT4
|
LEDs
|
15
|
UINT16
|
Serial link update interval [ms]
|
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
|
Hardware orientation
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
|
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.