Mindboards

Address 	Type 	Contents 

00 – 07H 	chars 	Sensor version number 
08 – 0FH 	chars 	Manufacturer 
10 – 17H 	chars 	Sensor type 
18 – 3DH 	bytes 	Not used 
3E, 3FH 	chars 	Reserved 

40H – 43H 	 s/long 	Motor 1 target encoder value, high byte first 
44H           byte      Motor 1 mode 
45H           s/byte    Motor 1 power 
46H           s/byte    Motor 2 power 
47H           byte      Motor 2 mode 
48 – 4BH 	 s/long     Motor 2 target encoder value, high byte first 
4C – 4FH 	 s/long     Motor 1 current encoder value, high byte first 
50 – 53H 	 s/long     Motor 2 current encoder value, high byte first 
54, 55H      word       Battery voltage 54H high byte, 55H low byte 
56H           S/byte    Motor 1 gear ratio 
57H           byte      Motor 1 P coefficient* 
58H           byte      Motor 1 I coefficient* 
59H           byte      Motor 1 D coefficient* 
5AH           s/byte    Motor 2 gear ratio 
5BH           byte      Motor 2 P coefficient* 
5CH           byte      Motor 2 I coefficient* 
5DH           byte      Motor 2 D coefficient* 

The Motor 1/2 mode fields select the operating mode for each channel.
The Motor 1/2 power fields set the operating power level for each channel. This value is a signed byte.
The Motor 1/2 target encoder value fields will accept a 32 bit target position setting for use in position setting mode. This value is a signed 32 bit value.
The Motor 1/2 current encoder value fields will return the 32 bits current encoder value. This value is a signed 32 bit value.
The Motor 1/2 gear ratio fields have not been implemented in the current version of the firmware.
The Motor 1/2 P coefficient fields specify the differential control loop P coefficient. This value is an unsigned byte.*
The Motor 1/2 I coefficient fields specify the differential control loop I coefficient. This value is an unsigned byte.*
The Motor 1/2 D coefficient fields specify the differential control loop D coefficient. This value is an unsigned byte.*
The Battery voltage field will return the current battery voltage. The high byte is the upper 8 bits of a 10 bit value. It may be used as an 8 bit representation of the battery voltage in units of 80mV. This provides a measurement range of 0 – 20.4 volts. The low byte has the lower 2 bits at bit locations 0 and 1 in the byte. This increases the measurement resolution to 20mV.
*Note: the preset PID coefficient values in the firmware have been tuned for the motors being used and it is recommended they not be changed. Any changes to these values will be lost at power down.

3.3. Channel mode
The motor controller has one mode control byte per channel to control and monitor its operation.
D7.... D6.... D5.... D4.... D3.... D2.... D1.... D0
Busy Error... - ...NTO . Rev .Lock .Sel 1 .Sel 0

Sel Action
00 Run with power control only
01 Run with constant speed
10 Run to position
11 Reset current encoder

The Run with constant speed command will cause the firmware to adjust the motor power to compensate for changing loads in order to maintain a constant motor speed.
The Run to position command will cause the firmware to run the motor to make the current encoder value to become equal to the target encoder value. It will do this using a maximum rotation rate as defined by the motor power byte. It will hold this position in a servo like mode until the Run to position command is changed or the target encoder value is changed. While the Run to position command is executing, the Busy bit will be set. Once the target position is achieved, the Busy bit will be cleared. There may be a delay of up to 50mS after a Run to position command is initiated before the Busy bit will be set.
The Reset current encoder will reset the current encoder value to 0 and then clear the command resulting in Off-braked state to be engaged.
The Lock bit is reserved and not implemented at this time.
The Rev bit may be used to alter the forward/reverse direction mapping for both the motor output and the encoder inputs. This function is primarily intended to harmonize the forward and reverse directions for motors on opposite sides of a skid-steer chassis.
The Error bit will be set if the motor controller has shut down due to a fault condition such as an output short circuit, output over-current or internal overheating has been detected. It will be cleared automatically after a one minute cool down period followed by a controller restart. The shut down function includes placing both motor channels into float mode.
The NTO or No Time Out bit may be set to stop the controller timing out if no I2C communication is received within 2½ seconds. In order to set the No Time Out state, the NTO bit must be set in both motor channel mode registers.

3.4. Channel power
The motor controller electronics is capable of operating each channel independently in PWM mode. This field may be set in the range of -100 to +100. 0 is used to set Off/Brake. Any value above 100 will be treated as 100, except –128 which is used to set Off/Float. Negative values run the motor in the reverse direction. The power should be set positive when being used as a parameter for the Run to position command. This field sets the rotation rate in Run with constant speed and maximum rotation rate in Run to position in the range of -1000 – +1000 degrees per second represented by the range -100 – +100. As with PWM mode, 0 is used to set Off/Brake while –128 is used to set Off/Float.
HiTechnic FIRST Motor Controller Specification

3.5. Channel current encoder value
The motor controller maintains a current encoder value for each motor channel. It is initialized to zero at power up and tracks all subsequent motor movement. It may be reset to zero using the Reset current encoder function. The encoder has a resolution of 1440 counts per revolution of the motor shaft or ¼ degrees per count.
3.6. Channel target encoder value
The motor controller uses this value to drive the motor to the target position when executing a Run to position command.

// NXTport=(0,1,2,3);  TXchannel= TetrixMuxChanell (0,1,2,3,4,5,6,7) 1*2 single motors up to 4*2 daisy chained

void TXMotorOn(NXTport, TXchannel, percentage)
void TxMotorTurn(NXTport, TXchannel, percentage, target)
void TXMotorCoast(NXTport, TXchannel)
void TXMotorBreak(NXTport, TXchannel)
long GetTXEncoderValue(NXTport, TXchannel)

void SetTXMotorSync(NXTport, TXchannel_master, TXchannel_slave, syncRatio)

The first motor controller in the daisy chain will use an I2C address of 02/03

The first motor controller in the daisy chain will use an I2C address of 02/03. Subsequent controllers will obtain addresses of 04/05, 06/07 and 08/09. Only four controllers may be daisy chained.