status data

Dexter status data

The status of the Dexter robot arm is returned to DDE by the Firmware after every command. All the _DELTA and _AT values are scaled by the calibration values in the AxisCal.txt file. DDE calculates additional status data and adds it to the status array¹ available to jobs. This includes slope values for each joint.

Units are always integer arc seconds. For each of the following "Joint..." sections:
*_AT - Current incremental position goal toward the commanded final position goal.
*_DELTA - Instantaneous error in position. Difference between _AT and actual position.
*_PID_DELTA - Accumulated corrective error signal. Related to force due to inertia, gravity, etc.
*_FORCE_DELTA - In follow mode, this is the offset from commanded position necessary to keep force at zero.
*_SIN - The current A2D value from the sin sensor on that joints encoder.
*_COS - The current A2D value from the cos sensor on that joints encoder.
PLAYBACK_ - Not used? The step and direction ticks sent to the motor in the time between status updates. August 2018 changed to Measured angle of the joint
SENT_ - Little used? Commanded position goal.
SLOPE_ - Unused. Was rate of change of _AT. Measurement of joint speed. April 2018 changed to servo information (see below)

In April 2018, the FPGA and Firmware (see line 2455) code was changed so that the Dynamixel servo data is returned in the SLOPE items as follows:
Joint 6 position replaces SLOPE_BASE_POSITION,
Joint 6 force replaces SLOPE_PIVOT_POSITION,
Joint 7 position replaces SLOPE_END_POSITION,
Joint 7 force replaces SLOPE_ANGLE_POSITION.

In August 2018, the FPGA and Firmware was changed to return the actual measured angle of each joint encoder as follows:
BASE_MEASURED_ANGLE replaces PLAYBACK_BASE_POSITION
PIVOT_MEASURED_ANGLE replaces PLAYBACK_PIVOT_POSITION
END_MEASURED_ANGLE replaces PLAYBACK_END_POSITION
ANGLE_MEASURED_ANGLE replaces PLAYBACK_ANGLE_POSITION
ROT_MEASURED_ANGLE replaces PLAYBACK_ROT_POSITION

Returned data

Address	Description
00	Job number
01	Instruction number
02	Start time
03	End time
04	Oplet (e.g. 'g')
05	?
06	DMA_READ_DATA
07	DMA_READ_DATA
08	RECORD_BLOCK_SIZE
09	END_EFFECTOR_IO_IN
	Joint 1: BASE
10	BASE_POSITION_AT
11	BASE_POSITION_DELTA
12	BASE_POSITION_PID_DELTA
13	BASE_POSITION_FORCE_DELTA
14	BASE_SIN
15	BASE_COS
16	PLAYBACK_BASE_POSITION (Now BASE_MEASURED_ANGLE)
17	SENT_BASE_POSITION
18	SLOPE_BASE_POSITION (Now Joint 6 angle)
	Joint 2: PIVOT
19	PIVOT_POSITION_AT
20	PIVOT_POSITION_DELTA
21	PIVOT_POSITION_PID_DELTA
22	PIVOT_POSITION_FORCE_DELTA
23	PIVOT_SIN
24	PIVOT_COS
25	PLAYBACK_PIVOT_POSITION (Now PIVOT_MEASURED_ANGLE)
26	SENT_PIVOT_POSITION
27	SLOPE_PIVOT_POSITION (Now Joint 6 force)
	Joint 3: END
28	END_POSITION_AT
29	END_POSITION_DELTA
30	END_POSITION_PID_DELTA
31	END_POSITION_FORCE_DELTA
32	END_SIN
33	END_COS
34	PLAYBACK_END_POSITION (Now END_MEASURED_ANGLE)
35	SENT_END_POSITION
36	SLOPE_END_POSITION
	Joint 4: ANGLE
37	ANGLE_POSITION_AT
38	ANGLE_POSITION_DELTA
39	ANGLE_POSITION_PID_DELTA
40	ANGLE_POSITION_FORCE_DELTA
41	ANGLE_SIN
42	ANGLE_COS
43	PLAYBACK_ANGLE_POSITION (Now ANGLE_MEASURED_ANGLE)
44	SENT_ANGLE_POSITION
45	SLOPE_ANGLE_POSITION
	Joint 5: ROT
46	ROT_POSITION_AT
47	ROT_POSITION_DELTA
48	ROT_POSITION_PID_DELTA
49	ROT_POSITION_FORCE_DELTA
50	ROT_SIN
51	ROT_COS
52	PLAYBACK_ROT_POSITION (Now ROT_MEASURED_ANGLE)
53	SENT_ROT_POSITION
54	SLOPE_ROT_POSITION