Hacker News Reader

Comment by ActorNightly | Hacker News Reader

General microcontroller questions if you don't mind.

Lets say that I prototype something on dev board like something from Raspberry Pi, or ones from STM. Now I want to do a full product, (like the Tiny Pilot) with the microprocessor on a custom PCB board with just the necessary hardware.

I understand that you have to design the schematic and then get the PCB layout done, but in terms of figuring out which pins to connect, is it just a matter of figuring it out from the microcontroller manual? Additionally, how do you end up programming the microcontrollers, do you have to have a separate programmer since you don't have all the stuff on the dev board?

View on HN

TinyPilot runs on the Raspberry Pi 4B, so I haven't made my own custom board yet.

The Voyager 2 will use custom PCBs for the HAT, but it will still be on top of the Pi.

In the next iteration, I'd like to use the Pi Compute Module to migrate to my own custom board, but I'll need to work with an EE firm on that, since I'm not knowledgeable enough about EE for that kind of project.

By the way, does Voyager 2 have its own CSI bridge, or are you planning to mount a ready-made module from Geekworm or another company next to your HAT?

All existing CSI bridges that you have used so far have two very serious problems: they do not work with audio capture and due to HDMI backpowering, your Raspberry may stop booting until you physically disconnect the cable. Backpowering is especially common when using KVM switches and some HDMI converters.

Both of these problems are solved on v3 HAT, thanks to our CSI bridge design. Are you planning to solve these problems? Just interesting :)

Voyager 2 uses the C779 bridge. I've heard of failure to boot when users chain TinyPilot to the AIMOS KVM, but I've never gotten reports of this being a problem otherwise.

There's no audio support, and audio would be a nice-to-have, but it's not my top priority at the moment.

I'd like to integrate the TC358743 onto the HAT itself, but Toshiba's got a huge lead time on orders right now.

> Lets say that I prototype something on dev board like something from Raspberry Pi, or ones from STM.

Worth noting that your typical STM32 MCU is quite different class of device compared to the Broadcom SoC on a RPi. From a architectural point of view, the big difference is that MCUs typically have both flash and ram integrated in the package, while SoC requires external ram and flash. Designing PCB for high-speed DDR memory is not trivial. Modern SoCs come in high-density BGA packages usually sporting close to thousand pins (or more!), while MCUs usually come in more easy to work with packages with order of magnitude less pins.

Specifically the Broadcom chip in current RPis is custom made and not generally available.

> I understand that you have to design the schematic and then get the PCB layout done, but in terms of figuring out which pins to connect, is it just a matter of figuring it out from the microcontroller manual?

yes. if you're using ST parts i suggest using their CubeMX tool, if only to figure out pin assignment. makes it way smoother.

i've seen multiple real projects with real engineers who should get this shit right screw up pin assignment.

also seen them just... not read the data sheet. i don't understand how they expected the board to work, but, it happened.

Yep! It's a matter of figuring it out from the microcontroller manual / datasheet (or basing your design on one that already has it figured out.)

Programming microcontrollers is done using an in-circuit programmer, which connects to a header on the board. Adafruit has a great tutorial for this: https://learn.adafruit.com/proper-step-debugging-atsamd21-ar...

> is it just a matter of figuring it out from the microcontroller manual?

pretty much, you might end up tweaking which pins you use when designing the pcb because the one on the other side of the chip is just as good, but it simplifies the routing and layout of the board significantly.

Reply on news.ycombinator.com