ANNOUNCING: navX MXP Robotics Navigation Sensor

[Thad House]

Originally Posted by slibert

Here's the issues we've seen so far:

(a) [LabView] an I2C bus hang when communicating w/the navX MXP using I2C (after a simulated stage 2 brownout) in a benchtop test configuration and,
(b) [Java] several I2C bus hangs on our competition robot when using the LIDAR Lite on the MXP I2C bus (in this case, we are currently suspicious of a noise issue corrupting a transmission on the I2C bus, but that hasn't been proven yet).

To get data again from these sensors in both cases required a Roborio reboot (restarting the roborio code did not resolve this issue). We've verified that a Roborio reboot does not cause the navX MXP to be rebooted (the MXP 5VDC rail stays powered across the reboot). This, combined w/the fact the issue occurs w/both LabView, and Java points to a Roborio-side problem, and perhaps at a level lower than the Roborio-side libraries. [All testing was performed w/the latest RoboRio firmware/software versions.]

Our next steps are to refine our test setup to find the simplest reproducible case that will hang the I2C bus (to identify the range of the of time during which a Stage 2 brownout can cause the I2C/SPI bus to hang, and try to get some more info on the bus line states and errors received on the RoboRio side) - and also to reproduce the SPI bus hang on the navX MXP you have mentioned. Once we've got that we'll package up the info and send it along to National Instruments.

Until a resolution is found, these are the recommendations:

- We haven't seen the MXP TTL UART communication path to the navX MXP get hung by the disconnect, so using the MXP TTL UART this is recommended for teams experiencing I2C/SPI bus hangs.

- As noted before, if keeping the navX MXP powered in the face of a Roborio Stage 2 brownout is needed, use the USB interface 5VDC/GND leads connected to a 5VDC, 500mA output from the VRM.

One question for you: have you any evidence of brownouts in your Driver Station Logs during the period of time when the I2C bus was hung? Or do you think another condition may be triggering this case?

It would not report data on bootup. And there was no way to check if it was actually reporting data until the field connected, and by that point we had to be off the field. We did have the USB cord plugged into the VRM, so I highly doubt our issues were caused by a brownout. Everytime we tested in the pits it came up correctly. Just on the field it would only come up about 70% of the time.