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.

Each data item is a signed 32 bit binary integer.

Units for angles are always integer arc seconds.

Joint Data Meanings

For each of the following "Joint..." sections (e.g. replace * in the following with J1...J5) in the status data:

Name	Description
*_AT	Current incremental position goal toward the commanded final position goal.
*_DELTA	Instantaneous error in position. Difference between _AT and actual position. Always gets corrected out to zero given drive strength to do so.
*_PID_DELTA	. Related to force due to inertia, gravity, etc.
*_FORCE_DELTA	In follow mode, this is the angular 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 the current 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 on some joints (see below)

Changes

In April 2018, the FPGA and Firmware (see line 2455) code was changed so that the Dynamixel servo data is returned by the getNormalizedInput function for 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.

Also, the SLOPE_ROT_POSITION was replaced with the error status of the two servos with J6 in the LSB and J7 in the next byte up (*256).

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	Sample
00	Job number	1
01	Instruction number	0
02	Start time 1	1531787828
03	End time 1	349602
04	Oplet (e.g. 'g')	103
05	ERROR	0
06	DMA_READ_DATA	0
07	DMA_READ_DATA	0
08	RECORD_BLOCK_SIZE	0
09	END_EFFECTOR_IO_IN (Type of end effector installed?)	0
	Joint 1: BASE
10	BASE_POSITION_AT	0
11	BASE_POSITION_DELTA	0
12	BASE_POSITION_PID_DELTA	0
13	BASE_POSITION_FORCE_DELTA	0
14	BASE_SIN	3703
15	BASE_COS	2967
16	PLAYBACK_BASE_POSITION (Now BASE_MEASURED_ANGLE)	0
17	SENT_BASE_POSITION	0
18	SLOPE_BASE_POSITION (Now Joint 7 measured angle)	0
19	empty	2147483647
	Joint 2: PIVOT
20	PIVOT_POSITION_AT	0
21	PIVOT_POSITION_DELTA	0
22	PIVOT_POSITION_PID_DELTA	0
23	PIVOT_POSITION_FORCE_DELTA	0
24	PIVOT_SIN	293
25	PIVOT_COS	56
26	PLAYBACK_PIVOT_POSITION (Now PIVOT_MEASURED_ANGLE)	0
27	SENT_PIVOT_POSITION	0
28	SLOPE_PIVOT_POSITION (Now Joint 7 torque)	0
29	empty	2147483647
	Joint 3: END
30	END_POSITION_AT	0
31	END_POSITION_DELTA	0
32	END_POSITION_PID_DELTA	0
33	END_POSITION_FORCE_DELTA	0
34	END_SIN	809
35	END_COS	3063
36	PLAYBACK_END_POSITION (Now END_MEASURED_ANGLE)	0
37	SENT_END_POSITION	0
38	SLOPE_END_POSITION (Now Joint 6 measured angle)	0
39	empty	2147483647
	Joint 4: ANGLE
40	ANGLE_POSITION_AT	0
41	ANGLE_POSITION_DELTA	0
42	ANGLE_POSITION_PID_DELTA	0
43	ANGLE_POSITION_FORCE_DELTA	0
44	ANGLE_SIN	1682
45	ANGLE_COS	3675
46	PLAYBACK_ANGLE_POSITION (Now ANGLE_MEASURED_ANGLE)	0
47	SENT_ANGLE_POSITION	0
48	SLOPE_ANGLE_POSITION (Now Joint 6 torque)	0
49	empty	2147483647
	Joint 5: ROT
50	ROT_POSITION_AT	0
51	ROT_POSITION_DELTA	0
52	ROT_POSITION_PID_DELTA	0
53	ROT_POSITION_FORCE_DELTA	0
54	ROT_SIN	1990
55	ROT_COS	218
56	PLAYBACK_ROT_POSITION (Now ROT_MEASURED_ANGLE)	0
57	SENT_ROT_POSITION	0
58	SLOPE_ROT_POSITION (Now J6/7 servo error codes)	0
59	empty	2147483647

Notes:

Times

Times are in seconds since 1970. e.g. 1531787828 is GMT: Tuesday, July 17, 2018 12:37:08 AM as per epochconverter.com

Note that Dexter may not have the correct current time. e.g. 349602 is GMT: Monday, January 5, 1970 1:06:42 AM or, in other words, a Dexter which has been running for a day, six minutes and 42 seconds.