Movado is a motion control software for Pico-2, which has been used in Infanoid and Keepon. Movado receives commands from a host PC through a serial communication line, and controls four DC motors with digital encoders in addition to another four RC-servos. A signle communication line can host up to 31 Pico-2s (hereafter "nodes"), which means you can control up to 124 DC motors and 124 RC-servos on a signel communication line. For details of connections with PC and motors, please refer to "ClayBot's Spec".

• Download: Motion control software Movado

This page describes the command protocol, by which you can control Movado from your PC.

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A command to Movado is a sequence of 6 byte data, called a "packet". As illustrated below, the first byte has its MSB=1, and the following 5 bytes have their MSB=0.

A packet consists of address (addr), motor number (n), instruction (inst), and 4 byte argument (quad).

• addr : 5bit (0~31) address, specifies the receiver of this packet. Pico-2's address is set by the on-board switches SW5~1; for example, SW5=on SW4=off SW3=off SW2=on SW1=off for address 0x12 (18). Note that address 0x1f (31) is reserved for broadcast.
• n : 2bit motor number (0~3), specifies the target motor to which the command applies.
• inst : 3bit instruction (0~7), describes in detail below.
• quad : 4byte (32bit) argument. Note that the 3rd to 6th bytes of a packet have its MSBs (m1~4) displaced to the 2nd byte. A quad has various meanings: 32bit fixed-point data (fix) for major commands, upper 16bit data and lower 16bit data for movac/movel commands, and 8bit jnst, 8bit index, and 16bit word for sub-commands.

The 32bit fixed-point data (fix) has a 16bit integer part (the upper 16bit of quad) and a 16bit fractional part (the lower 16bit of quad). The following C functions make conversion between fix and double.

typedef int fix;

fix  double2fix (double d) {
    return (fix) (d * 65536);
}

double  fix2double (fix f) {
    return f / 65536.0;
}

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When Movado received a command packet whose address matched Movado's address, Movado performs the command. There are 10 types of commands described as follows. Most commands operate on a motor specified by the address (addr) and the motor number (n).

• move (inst=0)
  Moves the specified motor to pos [rad] with Trapezoid Velocity Control. It uses prestored acceleration (by setacc) and maximum velocity (setvel).
• setacc (inst=1 and fix ≥ 0)
  Sets acceleration to acc [rad/s²] for the specified motor.
• movac (inst=1 and fix < 0)
  Moves the specified motor to pos [rad] with Trapezoid Velocity Control using acceleration −acc [rad/s²] and prestored maximum velocity (setvel). Note that pos and −acc are 16bit interger (no fractional part).
• setvel (inst=2 and fix ≥ 0)
  Sets maximum velocity to vel [rad/s] for the specified motor.
• setvel (inst=3)
  Sets goal position to pos [rad] for the specified motor. This causes a ballistic move.
• movel (inst=1 and fix < 0)
  Moves the specified motor to pos [rad] with Trapezoid Velocity Control using preset acceleration (setacc) and maximum velocity −vel [rad/s]. Note that pos and −vel are 16bit interger (no fractional part).
• sub (inst=4)
  Performs sub-command, whose details are described below.
• getacc (inst=5)
  Returns preset acceleration [rad/s²] for the specified motor.
• getvel (inst=6)
  Returns current velocity [rad/s] for the specified motor.
• getpos (inst=7)
  Returns current position [rad] for the specified motor.

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Sub-commands are described below. Some sub-commands (m in N/m column) operate on a specified motor (by addr and n); other sub-commands (N in N/m column) operate on a specified node (by addr).

Movado's internal parameters, like PID gains, can be set/get by the following sub-commands. To set 32bit parameters, you need to perform set_lower first, then set_upper To get 32bit parameters, you need to perform get_upper first, then get_lower. If you want to check completion of move/movac/movel, read CAMOD. If you want to check completion of calibration (described below), read MMFLG.

Movado has automatic calibration system for motors with incremental encoders. The set_zero command forces current position as zero (POS=0). The do_max/do_min commands move to positive/negative physical limit and store the position into MIN/MAX parameters. The do_minmax performs do_min first, then do_max. The do_minmaxcen performs do_minmax, then move to the center, and finally perform set_zero. The do_minmaxmax performs do_minmax, then move to the maximum position, and finally perform set_zero. The do_minmaxmin performs do_minmax, then move to the maximum position, and finally perform set_zero.

For do* commands, Movado uses the maximum velocity (setvel) for finding the physical limits. The parameter emg stands for "error magnitude". When motion delay exceeds the amount of motion for emg [ms] period, Movado detects it as a physical limit. In most cases, emg should be 100~200.

Movado can control up to 4 RC-servos in the similar way to DC motors. The commands move_rcs uses Trapezoid Velocity Control, whose acceleration and maximum velocity can be set by setacc_rcs and setvel_rcs; while, setpos_rcs makes a ballistic motion. For most RC-servos, 0x2400 is approximately at the center.

The reset command resets Movado. The get_report command is for reporting current position at a cycle of interval [ms] for count times. Having received get_report command, Movado starts reporting current positions when move/movac/movel/setpos is performed. The report will be in the same packet for getpos command.

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