Archives: 2020-03

Bringing up power on the quad pi3 hat

The first thing I needed to get working on the new quad’s raspberry pi3 hat, was the input DC/DC power converter.  One of the main functions of this board is to take the main DC bus voltage of around 20V, and provide the raspberry pi with 5V power.

In the previous iteration of this board, it was limited to an recommended maximum voltage of around 24V.  As with all the components in my hardware revisions I aimed to support a higher input voltage.  Here I switched parts to the Diodes AP64351 so that I could get to a recommended maximum voltage of 32V (the part’s absolute max is 40V).

New quad raspberry pi interface board

With the new FD-CAN based moteus controllers I need a way for the raspberry pi to communicate with them.  Thus I’ve got a new adapter board in house that I’m bringing up:

dsc_0339

This one has 5 independent FD-CAN channels, an IMU, a port for an nrf2401l RF transceiver as well as a buck converter to power the computer from the main battery bus.

The prototypes were largely constructed by MacroFab, although I did the Amass connectors and the STM32s because supply chain issues prevented me from getting those parts to MacroFab in time.

Programming a lot of fdcanusbs

To get ready for the initial limited release of fdcanusbs, I needed to program a whole bunch of them.  Further, I wanted to be able to scale up a few factors of two without being too annoyed with manual steps.  Thus, enter my minimal programming fixure:

dsc_0188

It isn’t much, just a raspberry pi 3b+, the official 7" rpi touch screen, a STM32 programmer, a “fixtured” fdcanusb to drive the device under test, and a label maker.  The touch screen is mostly there to display the results if anything goes awry, as in normal operation there is just one button to push.  The final cycle time to program a fdcanusb and install it into the enclosure is around two minutes, which is good enough for now.

fdcanusb up at mjbots.com

I’ve received my first production run of the fdcanusb CAN-FD USB adapters and they are up for sale at mjbots.com!

fdcanusb_angle

While this is necessary for interacting with the moteus controller, it is also a fine general purpose CAN-FD adapter.  At the moment, the USB interface is a platform independent line based serial one (Windows, Linux, MacOS).  It doesn’t yet interoperate with SocketCAN on linux, but hopefully that will be resolved in the not too distant future.