¶ Dynamixel Servo (Protocol 2)
This allows Dynamixel Servo motors to be used as axis motors. This document was written assuming XL430-250T servos were used, but other servo types that use Robotis Protocol 2 can probably be used (not tested). The servo's count range is mapped to the axis machine position (mpos) range. If your X axis servo has a count range from 0-4095, that would be mapped across the mpos range. If the range is 0-300 and you send G0X150 it will be told to go to count 2047.
Servo set up The servos must be set up with Dynamixel software first. The easiest way is to use the Dynamixel Wizard software. Here are the registers you probably want to set.
| Address | Name | Value | Description |
|---|---|---|---|
| 7 | ID | 1-253 | Must be unique |
| 8 | Baud Rate | 3 (1000000) | |
| 9 | Return Time Delay | 100 | Faster |
| 24 | Moving Threshold | 1 | Most Accurate |
| 48 (optional) | Max Position | 0-4095 | Limits rotation |
| 52 (optional) | Min Position | 0-4095 | Limits rotation |
If you stall a Dynamixel motor it will likely go into a faulted mode. The only way to recover is to power cycle them.
config values
¶ uart_num
- Type: Integer
- Default:
-1(must be set -- there is no usable default)
Which top-level uartN: section this servo's Protocol 2 bus runs over. Required. This should match the programmed baud of the servos -- 1000000 is recommended, mode 8N1.
¶ id
- Type: Integer
- Default:
255(must be changed -- this is Dynamixel's broadcast address, not a usable per-device value)
This servo's Protocol 2 device ID on the bus. Each must have a unique id.
¶ count_min
- Type: Integer
- Default:
1024
This is the location on the servo for the lower end of the mpos range.
¶ count_max
- Type: Integer
- Default:
3072
This is the location on the servo for the upper end of the mpos range.
¶ timer_ms
- Type: Integer
- Default:
50
Update interval, in milliseconds, for refreshing the servo's commanded position.
Direction reversal: Swap the count_min: and count_max: values.
Homing: The servo will immediately go to the homing/mpos_mm location of the axis.
Enable: The servos will disable whenever the motors disable (see the idle_ms config value). When they are disabled, you can move them by hand and the mpos will track the movement.
¶ Config Example
x:
steps_per_mm: 100.000
max_rate_mm_per_min: 5000.000
acceleration_mm_per_sec2: 50.000
max_travel_mm: 300.000
soft_limits: false
homing:
cycle: 2
positive_direction: false
mpos_mm: 0.000
feed_mm_per_min: 100.000
seek_mm_per_min: 200.000
settle_ms: 500
seek_scaler: 1.100
feed_scaler: 1.100
motor0:
limit_neg_pin: NO_PIN
limit_pos_pin: NO_PIN
limit_all_pin: NO_PIN
hard_limits: false
pulloff_mm: 1.000
dynamixel2:
id: 1
uart_num: 1
count_min: 1024
count_max: 3072