LewanSoul-xArm

The xArm has three means of communication.

HID-USB
TTL serial 9600 BAUD
Game Controller which appearently does not function even though the controller and adapter are provided.

USB Communications

Uses https://github.com/mikeobrien/HidLibrary.

xArm Controller USB Protocol

In general terms, a packet transmitted to the xArm will have the following format.

	id	header	length	command	parameters
Bytes	1	2	1	1	0 or more
Comments	Any number.	Always 0x5555.	Here to end.	See commands.	See commands.

Commands

Commands are essentially request packets embedded into USB HID reports.

USB HID reports generally have output and input data block lengths of 64 bytes. A USB HID report prepends an id byte so that messages spanning more than one block may be identified by their sequential block id. How how this is implemented is application specific. For purposes of controlling the xArm, a message never exceeds the maximum report length.

Requests and Reqponses are described in the following syntax:

Each field is seperated by a space.
Each field is described by the type in parentheses.
Curly braces denote that their content may be repeated more than once.

ServoOffsetRead (28)

Read the offset value of one or more servos.

Request: (byte)count { (byte)id }

Response: (byte)count { (byte)id (sbyte)offset }

Parameters: count is the number of servos in id list. id is one or more servo ids. offset is a signed byte with valid range of -128 to 128.

ServoMove             3  (byte)count (ushort)time { (byte)id (ushort)position }
GroupRunRepeat        5  (byte)group[255=all] (byte)times 
GroupRun              6  (byte)group (ushort)count[0=continuous]
GroupStop             7  -none-
GroupErase            8  (byte)group[255=all]
GroupSpeed           11  (byte)group (ushort)percentage
xServoOffsetWrite    12  *** not sure
xServoOffsetRead     13  *** not sure
xServoOffsetAdjust   14  *** not sure
GetBatteryVoltage    15  -none-; (ushort)millivolts
ServoOff             20  (byte)count { (byte)id }
ServoPositionRead    21  (byte)count { (byte)id }; (byte)count { (byte)id (ushort)position }
ServoPositionWrite   22  (byte)count { (byte)id (ushort)position }
ServoOffsetRead      23  (byte)count { (byte)id }; (byte)count { (byte)id (sbyte)offset }
ServoOffsetWrite     24  (byte)id (sbyte)offset
BusServoMoroCtrl     26  (byte)id (byte)??? (ushort)speed
BusServoInfoWrite    27  (byte)id (ushort)pos_min (ushort)pos_max (ushort)volt_min
                         (ushort)volt_max (ushort)temp_max (byte)led_status
                         (byte)led_warning
BusServoInfoRead     28  -none-; (byte)id (ushort)pos_min (ushort)pos_max (ushort)volt_min
                         (ushort)volt_max (ushort)temp_max (byte)led_status
                         (byte)led_warning (byte)dev_offset (ushort)pos (byte)temp
                         (ushort)volt

Dispatch Timers

List<DispatcherTimer> dispatchTimers is declared as a private property in MainWindow.cs only for possible future reference and is not used anywhere else.

InitializeDispatcherTimers() is declared in MainWindow() and initializes 16-millisecond and 300-millisecond timers.

The DispatcherTimer will append up to one Tick to the Interval specified if that period exceeds one Tick's period. A Tick seems to be about slightly faster than 1/60th of a second. Put another way, the Tick event will fire when the master Tick has occured, even if the specified period has been exceeded.

16msTick

This timer is the game loop for the application and has a nominal frequency of 60Hz. It has two functions:

Perform scope's UI updates.
Manage communication timing.

margyle / LewanSoul-xArm