roboarm

Code for interfacing and notes about the OWI-535 Robotic Arm

roboarm-simple.py

Really simple approach to creating a web interface to control the arm remotely. The single file will run whereever you have and open up a website on port 8080 that you can access directly from any device.

The table layout that is shown represents the layout of the actual arm in the simplest way - note, each activation in this simple interface ends any current action and lasts 1 second.

Interface

Visit http://<your-ip>:8080 and the table should be displayed. Confirmed working with Raspberry Pi (Server) and iPhone (client).

Gripper Open		Gripper Close
	Wrist Up
	Wrist Down
Base	Elbow Up	Base
CCW	Elbow Down	CW
	Shld. Up
	Shld. Down
Light On		Light Off

Preparation

You will need Python Bottle to get this working, but nothing else - it uses the reference Web Server included, but seems easy to change out for something else (see Bottle documentation: http://bottlepy.org/docs/dev/deployment.html). This works on the latest Raspbian on Raspberry Pi.

> sudo pip install --pre pyusb
> sudo pip install bottle
> sudo python roboarm-simple.py

PyUSB problems

See here for some further information: http://raspberrypi.stackexchange.com/questions/6774/installed-pyusb-still-importerror-no-module-named-core

http://stackoverflow.com/questions/22049399/how-to-install-pyusb-on-ubuntu

Thanks

@lizquilty - code from this implementation that is a direct copy of code from this system: https://github.com/lizquilty/roboticarm - full explanation of what is happening within the code.

roboarm-rest.py

This will be a more complex integration with the USB controller of the Robotic Arm - it will essentially allow for the system to run more that 1 motor at a time and will build on the roboarm-simple.py in two ways to achieve this: Updated interface and Protocol logic enhancement.

Web Interface

Todo: design RESTful interface to work with the on-off control provided by the new protocol logic.

Protocol Logic

Using the logic below, as found by @notbrainsurgery here: http://notbrainsurgery.livejournal.com/38622.html we can drive the motors independantly to create a more fully functional arm.

USB Interface

From the site above,

The device is controlled by 3 byte commands sent via USB control transfers. Command format is byte0, byte1, byte2. Each byte controls a group of arm features. All motors could be controlled independently. Most commands start action which is continued until next action is signalled. Byte '00' universally used as stop action.

Byte 0

This table helps represent the calculations requried for the first byte of the 3, this controls the main functions of the Arm Actuators:

• Shoulder (SH),
• Elbow (EL),
• Wrist (WR) and
• Gripper (GR)

and Actions:

• UP (Clockwise when viewed from the side),
• DW (Down, Counter-Clockwise),
• OP (Open, increase the width between the grippers),
• CL (Close, decrease the width)

Bit Number	Controls	All Stop	GR CL	GR OP	All UP	All DW	GR CL / EL UP	GR OP / SH DW	EL DW / WR UP / GR OP	Invalid
7	Shoulder: SH DW	0	0	0	1	0	0	1	0	1
6	SH UP	0	0	0	0	1	0	0	0	1
5	Elbow: EL DW	0	0	0	1	0	0	0	1	0
4	EL UP	0	0	0	0	1	1	0	0	0
3	Wrist: WR DW	0	0	0	1	0	0	0	0	0
2	WR UP	0	0	0	0	1	0	0	1	0
1	Gripper: GR OP	0	0	1	1	0	0	0	1	0
0	GR CL	0	1	0	0	1	1	1	0	0
Byte HEX		00	01	02	AA	55	11	81	26

Byte 1

This byte controls the Base (BS), turning the arm either

• CCW (Counter-clockwise when viewed from the side) or
• CW (Clockwise)

Bit Number	Controls	BS CCW	BS CW	BS Stop
7
6
5
4
3
2
1	Base: BS CCW	1	0	0
0	BS CW	0	1	0
Byte HEX		02	01	00

Byte 2

This byte controls the Light (LED) mounted behind the Gripper than can be useful for targetting:

• ON
• OFF

Bit Number	Controls	LED ON	LED OFF
7
6
5
4
3
2
1
0	Light: LED ON	1	0
Byte HEX		01	00