motor driver SPI protocol

2 octets packets : <register><value>
The next received packet was the controler value of the same register

Conciderating parameters :
	TORQUEF/SPEEDF
	00	01	10	11
PWMV	1	0	1	0
SPEEDV	0	1	0	1
TORQUEV	0	0	1	1

0x01 : CONFIG : config register
 bit 0 : commanding mode
  0 = analog mode
  1 = numerique mode

 bit 1 : ONOFF : switch motor on/off
  0 : power off
  1 : power on

 bit 2 : DIR : switch motor direction
  0 : default direction
  1 : reverse direction

 bit 3 : TORQUEF : control torque flag
  0 : disable, TORQUEH and TORQUEL are ignored
  1 : enable

 bit 4 : SPEEDF : control speed flag
  0 : disable, SEEPDH and SEEPDL are ignored
  1 : enable, PWMH and PWML are ignored

bit 5 : ARAMPF : acceleration ramping flag
  0 : disable
  1 : enable

bit 6 : DRAMPF : decceleration ramping flag
  0 : disable
  1 : enable

PWMV value, 10bits
0x10 : PWMH<1:0> : MSB of PWM duty
0x11 : PWML<7:0> : LSB of PWM duty

TORQUEV value, 16bits
0x20 : TORQUEH : MSB of torque setpoint
0x21 : TORQUEL : LSB of torque setpoint

SPEEDV value, 16bits in RPM
0x30 : SPEEDH : MSB of speed setpoint
0x31 : SPEEDL : LSB of speed setpoint

ARAMPV value, 16bits in milli-seconds
0x40 : ARAMPH : MSB of acceleration ramp time
0x41 : ARAMPL : LSB of acceleration ramp time

DRAMPV value, 16bits in milli-seconds
0x50 : DRAMPH : MSB of decceleration ramp time
0x51 : DRAMPL : LSB of decceleration ramp time