Robotino3 IO protocol

From RobotinoWiki

Contents

Description of the data exchange protocol between LPC2378 and COM-Express module over USB

Most of the I/Os comming with Robotino 3 are still connected to a NXP LPC2378 microcontroller (MC). In contrast to previous versions of Robotino the interface between the MC and Robotino's internal industral PC is no longer RS232 but USB. This page describes the protocol used for communication between MC and PC over USB.

Package assembly

All data send from PC to MC and vice versa has the form

Field name Bytes Description
Head 1 Start of package
Length 2 Length of package payload
Payload Payload data
Checksum 2 Calculated from length and payload bytes

Head

The package header is the unique byte 0xAA.

Length

The number of bytes of the (not escaped) payload data.

package[1] = length & 0xFF;
package[2] = 0xFF & ( length >> 8 );

Payload

The package payload data. The payload is composed of one or more commands. The payload send to the LPC2378 must not be larger than 128 bytes.

Checksum

Complement 2 of the sum of Length and Payload bytes before escaping.

uint16 calculate_checksum( const uint8* data, int dataSize )
{
  uint16 out = 0;
  for( int i=0; i<dataSize; ++i )
  {
    out += *p;
    ++data;
  }
  return 0xffff & ( (1<<16) - out );
}

Data escaping

The Head byte 0xAA must be unique through out all data send. By this the receiver knows that whenever it reads 0xAA that a new package begins. This is achieved by going through all the Length, Payload and Checksum bytes and whenever 0xAA or the escape byte 0x55 is found this byte is prefixed with 0x55 and the byte is xored with 0x20.

uint8* data; //the complete package data (Head, Length, Payload, Checksum)
uint8* escapedData; //buffer big enough to hold the escaped package data
for( int i=1; i<numBytesInData; ++i ) //not that we are starting at 1, we do not escape the Head
{
  if( 0xAA == *data || 0x55 == *data )
  {
    *(escapedData+++) = 0x55;
    *(escapedData++) = ( *data ^ 0x20 );
  }
  else
  {
    *(escapedData++) = *data;
  }
  ++data;
}

When reading an escaped package look for the escape byte 0x55. When you found 0x55 in the stream read the next byte and xor it with 0x20 to get the unescaped value.

QByteArray read( int length ) const
{
  QByteArray ba( length, 0 );
  int i=0;
  while( i<length )
  {
    char ch = 0;
    if( 1 != _serial->read( (unsigned char*)&ch, 1 ) )
    {
      throw ParserException( "Error reading 1 byte" );
    }
    if( 0x55 == ch )
    {
      if( 1 != _serial->read( (unsigned char*)&ch, 1 ) )
      {
        throw ParserException( "Error reading 1 byte" );
      }
      ba[i] = ( ch ^ 0x20 );
    }
    else if( 0xAA == ch )
    {
      throw ParserException( "Found HEAD" );
    }
    else
    {
      ba[i] = ch;
    }
    ++i;
  }
  return ba;
}

Commands

Field name Bytes Description
Tag 1 The command tag
Length 1 Number of bytes of command data
Data The command data. If Length=0 there is no Data field at all.

GET_HW_VERSION

Name Value Command data Description Direction
GET_HW_VERSION 1 none Requesting the hardware version PC->MC

HW_VERSION

Name Value Command data Description Direction
HW_VERSION 2 String Response to GET_HW_VERSION MC->PC

GET_SW_VERSION

Name Value Command data Description Direction
GET_SW_VERSION 3 none Requesting the software version PC->MC

SW_VERSION

Name Value Command data Description Direction
SW_VERSION 4 String Response to GET_SW_VERSION MC->PC

GET_DISTANCE_SENSOR_READINGS

Name Value Command data Description Direction
GET_DISTANCE_SENSOR_READINGS 5 none Requesting the readings of all infrared distance sensors PC->MC

DISTANCE_SENSOR_READINGS

Name Value Command data Description Direction
DISTANCE_SENSOR_READINGS 6
Byte Type Description
0-3 float32 ADC reading in Volts of distance sensor 0

...

32-35 float32 ADC reading in Volts of distance sensor 8
Response to GET_DISTANCE_SENSOR_READINGS. MC->PC

SET_MOTOR_SPEED

Name Value Command data Description Direction
SET_MOTOR_SPEED 9
Byte Type Description
0 uint8 motor number
1-2 int16 speed set-point in rpm (rounds per minute)
Set the speed set-point for one motor PC->MC

GET_ALL_MOTOR_SPEEDS

Name Value Command data Description Direction
GET_ALL_MOTOR_SPEEDS 10 none Requesting the speed of all motors PC->MC

ALL_MOTOR_SPEEDS

Name Value Command data Description Direction
ALL_MOTOR_SPEEDS 11
Byte Type Description
0-1 int16 speed of motor 0 in rpm

...

6-7 int16 speed of motor 3 in rpm
Response to GET_ALL_MOTOR_SPEEDS. MC->PC

SET_MOTOR_POSITION

Name Value Command data Description Direction
SET_MOTOR_POSITION 12
Byte Type Description
0 uint8 motor number
1-4 int32 motor position in encoder ticks
Set the position counter of one motor PC->MC

GET_ALL_MOTOR_POSITIONS

Name Value Command data Description Direction
GET_ALL_MOTOR_POSITIONS 13 none Requesting the position of all motors PC->MC
ALL_MOTOR_POSITIONS 14
Byte Type Description
0-3 int32 position of motor 0

...

12-15 int32 position of motor 4
Response to GET_ALL_MOTOR_POSITIONS. MC->PC

SET_MOTOR_PID_PARAMETERS

Name Value Command data Description Direction
SET_MOTOR_PID_PARAMETERS 15
Byte Type Description
0 uint8 motor number
1-4 float kp (a value less than 0 sets kp to the build in default)
5-8 float ki (a value less than 0 sets ki to the build in default)
9-12 float kd (currently not used)
Set PID parameters of one motor. PC->MC

GET_ALL_MOTOR_PID_PARAMETERS

Name Value Command data Description Direction
GET_ALL_MOTOR_PID_PARAMETERS 16 none Requesting the PID controller parameters of all motors PC->MC

ALL_MOTOR_PID_PARAMETERS

Name Value Command data Description Direction
ALL_MOTOR_PID_PARAMETERS 17
Byte Type Description
0-3 float kp of motor 0
4-7 float ki of motor 0
8-11 float kd of motor 0

...

35-39 float kp of motor 3
40-43 float ki of motor 3
44-47 float kd of motor 3
Response to GET_ALL_MOTOR_PID_PARAMETERS. MC->PC

SET_ALL_DIGITAL_OUTPUTS

Name Value Command data Description Direction
SET_ALL_DIGITAL_OUTPUTS 18
Byte Type Description
0 uint8 each bit reflects the setting of one digital outputs port at Robotino's IO connector
Set digital output ports at Robotino's IO connector. PC->MC

SET_ALL_RELAYS

Name Value Command data Description Direction
SET_ALL_RELAYS 19
Byte Type Description
0 uint8 bit 0 is the set-state of relay 0 at Robotino's IO connector

bit 1 is the set-state of relay 1 at Robotino's IO connector

Set the relays at Robotino's IO connector. PC->MC

SET_ODOMETRY

Name Value Command data Description Direction
SET_ODOMETRY 20
Byte Type Description
0-3 float x-position in meters
4-7 float y-position in meters
8-11 float rotation in radians
Set the odometry to the given pose PC->MC

SET_ODOMETRY_ROTATION

Name Value Command data Description Direction
SET_ODOMETRY_ROTATION 21
Byte Type Description
0-3 float rotation in radians
Set the odometry to the given rotation. Used when a gyroscope is connected to the PC to forward the gyroscope readings to the MC where the odometry is processed. PC->MC

GET_ODOMETRY

Name Value Command data Description Direction
GET_ODOMETRY 22 none Request odometry readings from the MC PC->MC

ODOMETRY

Name Value Command data Description Direction
ODOMETRY 23
Byte Type Description
0-3 float x-position in meters
4-7 float y-position in meters
8-11 float rotation in radians
Response to GET_ODOMETRY MC->PC

GET_ALL_MOTOR_CURRENT_READINGS

Name Value Command data Description Direction
GET_ALL_MOTOR_CURRENT_READINGS 26 none Request current readings from all motors PC->MC

ALL_MOTOR_CURRENT_READINGS

Name Value Command data Description Direction
ALL_MOTOR_CURRENT_READINGS 27
Byte Type Description
0-3 float32 Current in Ampere drawn from motor 0

...

12-15 float32 Current in Ampere drawn from motor 3
Response to GET_ALL_MOTOR_CURRENT_READINGS. MC->PC

GET_ALL_ANALOG_INPUTS

Name Value Command data Description Direction
GET_ALL_ANALOG_INPUTS 32 none Request all analog input readings. PC->MC

ALL_ANALOG_INPUTS

Name Value Command data Description Direction
ALL_ANALOG_INPUTS 33
Byte Type Description
0-3 float32 ADC readings in Volts from analog input port 1

...

32-35 float32 ADC readings in Volts from analog input port 8
Response to GET_ALL_ANALOG_INPUTS. Readings of all analog input ports. MC->PC

GET_ALL_DIGITAL_INPUTS

Name Value Command data Description Direction
GET_ALL_DIGITAL_INPUTS 34 none Request all digital input readings. PC->MC

ALL_DIGITAL_INPUTS

Name Value Command data Description Direction
ALL_DIGITAL_INPUTS 35 uint8 Response to GET_ALL_DIGITAL_INPUTS. Readings of all digital input ports. MC->PC

GET_BUMPER

Name Value Command data Description Direction
GET_BUMPER 36 none Request all digital input readings. PC->MC

BUMPER

Name Value Command data Description Direction
BUMPER 37 uint8 Response to GET_BUMPER. The bumpers state. MC->PC

GET_POWER_BUTTON

Name Value Command data Description Direction
GET_POWER_BUTTON 38 none Request all digital input readings. PC->MC

POWER_BUTTON

Name Value Command data Description Direction
POWER_BUTTON 39 uint8 Response to GET_POWER_BUTTON. The power button state. MC->PC

SET_FPGA_POWER

Name Value Command data Description Direction
SET_FPGA_POWER 40 uint8 Set the FPGA to hold the power supply PC->MC

GET_FPGA_POWER

Name Value Command data Description Direction
GET_FPGA_POWER 41 none Get the FPGA power supply hold status PC->MC

FPGA_POWER

Name Value Command data Description Direction
FPGA_POWER 42 uint8 Response to SET_FPGA_POWER and GET_FPGA_POWER. The FPGA power supply hold status. MC->PC

GET_PWR_OK_STATE

Name Value Command data Description Direction
GET_PWR_OK_STATE 43 uint8 Request status of the PWR_OK line. PC->MC

PWR_OK_STATE

Name Value Command data Description Direction
PWR_OK_STATE 44 uint8 Response to GET_PWR_OK_STATE. Power OK status signal generated by the ATX power

supply to notify the module that the DC operating voltages are within the ranges required for proper operation.

MC->PC

SET_PWR_OK_STATE

Name Value Command data Description Direction
SET_PWR_OK_STATE 45 uint8 Set the PWR_OK line. PC->MC

SET_PWM

Name Value Command data Description Direction
SET_PWM 46
Byte Type Description
0 uint8 PWM output of the LPC2378. Number in range [1-6].
1 uint8 PWM ratio. 0 is signal constant low. 255 is signal constant high.
Set the PWM ratio of a single PWM output. PC->MC

SET_MOTOR_ON

Name Value Command data Description Direction
SET_MOTOR_ON 47
Byte Type Description
0 uint8 Number of motor in range [0-3].
1 uint8 0 switches off the high side of the motor's H-bridge. 1 switches the high side of the motor's H-bridge on.
Enable/Disable a single motor. PC->MC

SET_PWRBTN

Name Value Command data Description Direction
SET_PWRBTN 48 uint8 Set PWRBTN# line. Power button low active signal used to wake up the

system from S5 state (soft off). This signal is triggered on the falling edge.

PC->MC

SET_SYS_RESET

Name Value Command data Description Direction
SET_SYS_RESET 49 uint8 Reset input signal. This signal may be driven to low

by external circuitry such as a reset button to hold the system module in hardware reset.

PC->MC

GET_COM_EXPRESS_STATES

Name Value Command data Description Direction
GET_COM_EXPRESS_STATES 50 none Request status of the COM Express status lines. PC->MC

COM_EXPRESS_STATES

Name Value Command data Description Direction
COM_EXPRESS_STATES 51
Byte Type Description
0 uint8 SUS_S3#. S3 Sleep control signal indicating that the system

resides in S3 state (Suspend to RAM).

1 uint8 SUS_S4#. S4 Sleep control signal indicating that the system

resides in S4 state (Suspend to Disk).

2 uint8 SUS_S5#. S5 Sleep Control signal indicating that the system

resides in S5 State (Soft Off).

3 uint8 THRM#. Thermal Alarm active low signal generated by the

external hardware to indicate an over temperature situation. This signal can be used to initiate thermal throttling.

4 uint8 THRMTRIP#
Response to GET_COM_EXPRESS_STATES. MC->PC

GET_ALL_MOTOR_READINGS

Name Value Command data Description Direction
GET_ALL_MOTOR_READINGS 52 none Request speeds, positions, currents from all motors. PC->MC

ALL_MOTOR_READINGS

Name Value Command data Description Direction
ALL_MOTOR_READINGS 53
Byte Type Description
0-1 int16 speed of motor 0 in rpm.

...

6-7 int16 speed of motor 4 in rpm.
8-11 int32 position of motor 0.

...

20-23 int32 position of motor 4.
24-27 float32 Current in Ampere drawn from motor 1.

...

36-39 float32 Current in Ampere drawn from motor 4.
Response to GET_ALL_MOTOR_READINGS. MC->PC

GET_IP_ADDRESS

Name Value Command data Description Direction
GET_IP_ADDRESS 54 none Request IP4 address. PC->MC

IP_ADDRESS

Name Value Command data Description Direction
IP_ADDRESS 55
Byte Type Description
0-3 uint32 IP address
4-7 uint32 Netmask
Response to GET_IP_ADDRESS. MC->PC

SET_IP_ADDRESS

Name Value Command data Description Direction
SET_IP_ADDRESS 56
Byte Type Description
0-3 uint32 IP address
4-7 uint32 Netmask
Set IP4 address. PC->MC

SET_EMERGENCY_BUMPER

Name Value Command data Description Direction
SET_EMERGENCY_BUMPER 57 uint8 1 enables the emergency bumper feature. 0 disables it. If enabled all motors are stopped for 2s if the Robotino's bumper is hit. PC->MC


SET_MOTOR_MODE

Name Value Command data Description Direction
SET_MOTOR_MODE 58
Byte Type Description
0 uint8 motor
1 uint8 mode
  • 0: velocity control mode
  • 1: position control mode
  • 2: gripper mode (only accepted for motor 3)
Set the control mode of one motor. PC->MC


RESET_LPC

Name Value Command data Description Direction
RESET_LPC 59
Byte Type Description
0 uint8
  • 0: Simple reset
  • 1: Enter USB bootloader
Reset the LPC2378 microcontroller. PC->MC

POWER_OFF

Name Value Command data Description Direction
POWER_OFF 60 none Power off the system. PC->MC

SET_POWER_SOURCE

Name Value Command data Description Direction
SET_POWER_SOURCE 61
Byte Type Description
0 uint8
  • 0: External power
  • 1: Battery pack 1
  • 2: Battery pack 2
  • 3: Battery pack 3
Select the systems power source. PC->MC

GET_POWER_SOURCES

Name Value Command data Description Direction
GET_POWER_SOURCES 62 none Request the list of available power sources. PC->MC

POWER_SOURCES

Name Value Command data Description Direction
POWER_SOURCES 63
Byte Type Description
0 uint8 Boolean indicating if external power supply is availabe
1 uint8 Boolean indicating if battery pack 1 is availabe
2 uint8 Boolean indicating if battery pack 2 is availabe
3 uint8 Boolean indicating if battery pack 3 is availabe
Response to GET_POWER_SOURCES. MC->PC

GET_POWER_SOURCE_READINGS

Name Value Command data Description Direction
GET_POWER_SOURCE_READING 64
Byte Type Description
0 uint8 Power source number. See SET_POWER_SOURCE.
Request readings of the power source. PC->MC

POWER_SOURCE_READINGS

Name Value Command data Description Direction
POWER_SOURCE_READINGS 65
Byte Type Description
0 uint8 Power source number.
1-4 float32 Power source voltage
5-8 float32 Power source current
9-12 float32 Power source remaining capacity
13-16 float32 Power source temperature
17 uint8 Battery type
  • 0: Lead acid battery
  • 1: NiMH battery
18 uint8 State of charge
19 uint8 Error
20-23 float32 Charging voltage
24-27 float32 Charging current
Response to POWER_SOURCE_READINGS. MC->PC

SET_MOTOR_ACCEL_LIMITS

Name Value Command data Description Direction
SET_MOTOR_ACCEL_LIMITS 66
Byte Type Description
0 uint8 motor number
1-4 float minimum acceleration in rpm/s
5-8 float maximum acceleration in rpm/s
Set the motor's minimum and maximum acceleration PC->MC

MOTOR_ACCEL_LIMITS

Name Value Command data Description Direction
MOTOR_ACCEL_LIMITS 67
Byte Type Description
0 uint8 motor number
1-4 float minimum acceleration in rpm/s
5-8 float maximum acceleration in rpm/s
Response to GET_MOTOR_ACCEL_LIMITS MC->PC

GET_MOTOR_ACCEL_LIMITS

Name Value Command data Description Direction
GET_MOTOR_ACCEL_LIMITS 68
Byte Type Description
0 uint8 Motor number.
Request motor's acceleration limits. PC->MC

INFO

Name Value Command data Description Direction
INFO 250 String Transmitted to inform about some event. MC->PC

WARNING

Name Value Command data Description Direction
WARNING 251 String Transmitted in case of a warning. MC->PC

ERROR

Name Value Command data Description Direction
ERROR 252 String Transmitted in case of a communication error. MC->PC

Data types

Name Number of bytes Description
String Depends of the TAGs data length Seqeunce of characters. The string is not terminated by 0.
uint8 1 Unsigned character
int8 1 Signed character
uint16 2 Unsigned short. Serialization is little endian.
int16 2 Signed short. Serialization is little endian.
uint32 4 Unsigned int. Serialization is little endian.
int32 4 Signed int. Serialization is little endian.
float32 4 Floating point number single precision. Serialization is little endian.
//encoding
char* data;
float f = 1.23f;
char* p = (char*)&f;
encodingData[0] = *(p++);
encodingData[1] = *(p++);
encodingData[2] = *(p++);
encodingData[3] = *(p++);

//decoding
float f2;
p = (char*)&f2;
*(p++) = encodingData[0];
*(p++) = encodingData[1];
*(p++) = encodingData[2];
*(p++) = encodingData[3];

Communication example

Communication between PC and MC is driven from the PC. Initially the PC will ask for the hardware and software version of the MC.

Byte number Value Description
0 0xAA HEAD
1 0x04 Package length low byte
2 0x00 Package length high byte
3 0x01 GET_HW_VERSION
4 0x00 Data length of GET_HW_VERSION
5 0x03 GET_SW_VERSION
6 0x00 Data length of GET_SW_VERSION
7 ? Checksum low byte
8 ? Checksum high byte

Answer from MC

Byte number Value Description
0 0xAA HEAD
1 0x0E Package length low byte
2 0x00 Package length high byte
3 0x02 HW_VERSION
4 0x05 Data length of HW_VERSION
5 0x33 "3"
6 0x2E "."
7 0x30 "0"
8 0x2E "."
9 0x30 "0"
10 0x04 SW_VERSION
11 0x05 Data length of SW_VERSION
12 0x33 "3"
13 0x2E "."
14 0x30 "0"
15 0x2E "."
16 0x30 "0"
17 ? Checksum low byte
18 ? Checksum high byte