Troubleshooting
When powering on Dexter, you should see a series of lights. The processor board has 3 bright LEDs.
- green lights when the processor board is getting power.
- blue lights when the FPGA is programmed and ready for operation.
- red lights during disk access (to the SD card.)
If you don't see any light, the power adapter may be disconnected, defective, etc...
- Check that the power adapter has a light on it. If it doesn't, check the wall outlet, power strip, etc... If it does have a light, check the cord to the robot, and the power connection there. If you don't find any obvious issues, the power brick may be defective, or the MicroZed board may be burned out. Testing the voltage output with a multimeter might be an option.
If you see the green light, but don't see the blue or red light, check that the jumpers are on correcting on the MicroZed board. These are in the lower left corner, and control how the board boots. To boot from the SD card, the jumpers must be set as follows: JP1: 1-2, JP2: 2-3, JP3: 2-3
The SD Card is difficult to insert and can easily be partially inserted or just fall out. It is on the opposite side of the MicroZed board from the USB Micro B at the bottom of the PCB, just left of center. If you have a fan installed for the stepper drivers, you will need to remove it. The contacts of the SD Card should be facing you, and pointing upward.
The SD Card can be difficult to get into the socket correctly and can easily be partially inserted or just fall out. It is on the opposite side of the MicroZed board from the USB Micro B at the bottom of the PCB, just left of center. If you have a fan installed for the stepper drivers, you will need to remove it. You can't really see the socket to get the correct orientation, so make sure the contacts of the SD card are facing you, and on the top.
When you push it up, it may jam or want to twist to the side. Keep moving it around a bit until you can feel it working against a spring, and moving up and down smoothly then press it in until it sort of clicks, not that you will hear the click, but it will suddenly not press back against you as you lower your finger, and you can press it up again and it will release, then again and it will stay.
If the robot doesn't seem to be booting, or you can't connect via DDE or ping, a great way to troubleshoot is by using the built in console port. This will allow you to watch the MicroZed board boot (which it will start to do even without an SD Card) and so you can see exactly where it stops or what error messages it displays. For detailed directions see Dexter USB Connection
After calibration, when going into a closed loop mode where the Encoders are feeding position information into the FPGA to correct each joint to an exact location, one or more joints may start to shake or vibrate, and may squeal and lose position badly. Here is a video of a customers Dexter in that state.
Most often, this is caused by a problem with the encoder. E.g. an LED or photosensor has come out of the hole in the encoder block, the encoder block has been pulled out of mesh with the disk, a connector is loose or a wire broken, or the encoder is simply not calibrated correctly.
To diagnose this, in DDE, from the "Calibrate Dexter..." dialog on the "Jobs" menu, do the eye calibration for the affected joint. Here is an example of an encoder which is NOT working correctly:
And here is another example of one that is correct (after being fixed) showing the "eye" and the correct center dot placed by the user.
Here is an example of a Sensor that was accidentally pulled out of it's hole in the encoder block:
Replacing it and hot glueing it in place corrected the example issue shown with the eyes above.