CAN termination¶
A CAN bus needs a 120 Ω resistor at each of its two ends. The gripper's driver has one, on a switch. The gripper is normally the last node on a robot's bus, where the switch must be ON.
| The gripper is | Switch |
|---|---|
| the last node on a robot's bus, at the end of the arm | ON |
| alone on a bench bus with the CANvas adapter (which has its own termination) | ON |
| in the middle of a bus, with other nodes after it | off |
To change it, unplug the supply, touch earthed metal (static electricity damages the driver) and unscrew the coupler connector: the switch is on the Spectral Micro driver inside the body, next to its CAN connectors; ON connects the resistor. The driver's connector page shows where it is on the board.
A bus with the right termination measures about 60 Ω between CANH and CANL with everything unpowered. A missing or doubled termination shows up as lost frames and a gripper that answers only sometimes.
Check
About 60 Ω between CANH and CANL, unpowered. About 120 Ω: one end is not terminated; about 40 Ω: three terminations are on.
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