Switching the WAM Between Internal & External Control

The WAM is controlled from a real-time operating system (RTOS) and a set control rate (usually 500 Hz, but configurable up to 1 kHz depending on the hardware configuration). Newer WAMs (types D and E) include a built-in PC-104 embedded computer in their base, which is loaded with a suitable RTOS to control the WAM at up to 750 Hz. Customers can communicate with this internal PC using Ethernet for asynchronous control. Barrett also sells modern Linux desktop PCs pre-loaded with a suitable RTOS (most recently, Xenomai under Ubuntu Linux), which communicates directly with the WAM's Puck motor controllers to control the WAM.

Here is a summary of the pros and cons of using each option:

Internal PC104	External PC
WAM is entirely self-contained	External desktop PC required
No expansion options	2 PCI expansion slots (or more in custom installation)
750 Hz maximum control rate	1 kHz maximum control rate
Command-line access only	Full desktop PC; easier to develop on

Switching Modes

Newer WAMs which include an embedded internal PC (types D and E) include internal switches to select which mode is to be used. Warning: Never alter the switches while the system is on; doing so may do irreparably damage the safety board. Always switch off the WAM's power supply first!

AE Safety Board (WAM Type E)

There are two revisions of Type E safety boards, AE-02 and AE-03. The AE-02 model supports the older BH8-262 grasper and contains more parts than the AE-03 model, which supports the BH8-280 grasper. These are shown below for comparison.

Safety Board Rev.AE-02 (supports BH8-262)	Safety Board Rev.AE-03 (supports BH8-280)

To switch between internal and external control, orient yourself to face the flat side of the WAM base. Unclip the four outer cover clips (two on each side) and remove the single screw on the top-left of the back cover with a 4mm hex wrench. Flip down the rear cover. Switches C and D control the CAN routing, as shown in the images above. Use the following table to select the correct positions (they are the same for both revisions of the board).

	Switch C	Switch D
Internal (PC-104)	IN	IN
External (Desktop PC)	OUT	OUT

Warning: Never alter the switches while the system is on; doing so may do irreparably damage the safety board. Always switch off the WAM's power supply first!

Note: It is possible to control two WAMs from one PC-104 internal PC. You will need a special cable to connect the WAMs via the external CAN connectors on the back of each system (contact Barrett for information). Configure the slave system for External control. Configure the master system for Internal control. In addition, you will need to toggle switch E in the master system underneath the safety board cover. Switch E is normally OUT, switch this to IN on the master system. Occasionally switch E is not stuffed correctly on the safety board. The default position is OFF, which is usually OUT. If switch E on your safety board is IN to begin with, your switch is backwards and you must reverse the switch E positions noted above. This does not apply to the other switches.

AD Safety Board (WAM Type D)

There are very few AD boards in the field at this time, so we will not post instructions here. Please contact support@… if you need assistance configuring your AD safety board.