mirror of
https://github.com/Architeuthis-Flux/JumperlessV5.git
synced 2025-09-05 10:47:58 +00:00
153 lines
7.6 KiB
Markdown
153 lines
7.6 KiB
Markdown
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# Jumperless V5: A Series Of Tubes
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So the Jumperless V5 Beta units have been lovingly received by my favorite group of nerds, and of course the first thing each of them wants to do is something I hadn't even thought of, let alone write firmware to support. Which is exactly why these beta tests are so great.
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Most of the coolest functionality of Jumperless comes from just hanging out with [the community](https://discord.gg/bvacV7r3FP).
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It usually goes something like:
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```
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User > Hey, can jumperless do [thing]?
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Me > No
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Me > Oh wait it totally could, hold on
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~ a few minutes later ~
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Me > Okay open the app and let it auto-update the firmware
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```
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The most recent one of these happened yesterday, and it resulted in an upgrade to the way it handles USB-Serial passthrough that I didn't think was even *possible*, let alone something that works so nicely you simply don't have to think about it.
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## Serial Passthrough
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The [RP2350 supports **_32_ USB endpoints**](https://datasheets.raspberrypi.com/rp2350/rp2350-datasheet.pdf#page=1138) which is USB-speak for one device showing up to your computer as if it was multiple devices, so you can talk to each of them separately. Jumperless V5 uses 3 of them (for now) and appears as 3 separate ports; Port 1 speaks directly to the onboard RP2350B for [making connections and generally controlling the thing](https://www.crowdsupply.com/architeuthis-flux/jumperless-v5/updates/jumperless-probelessly), Port 2 is the MicroPython REPL (I will talk about that in a future update), and Port 3 is the routable UART. Anything you send to that port gets passed right through to wherever you connect your Jumperless's Tx and Rx lines.
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How do you hook up the routable UART lines?
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Like this:
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*You can set those 4 user pads on the logo to do whatever you want, but here they're set to Tx / Rx*
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Then you can open up any IDE you like, select Jumperless V5's third port, and it acts just like your dev board was plugged in with its own USB cable.
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It even grabs the special hardware flow control signals (RTS/CTS/DTR) and does the proper things with them to trigger the reset lines, you can also attach them to a GPIO and route them anywhere to flash chips that aren't in the Nano header.
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## The Ask... Or: How I Learned To Quit Worrying And Love UPDI
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The first thing one of the beta testers wanted to do, was flash an ATTiny412 with UPDI.
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To program the newer AVR chips, Microchip uses a protocol called Universal Program and Debug Interface, which is really just UART (Universal Asychronous Receiver / Transmitter) with the Tx and Rx lines connected together.
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>[!NOTE]
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>I love the new AVR chips, in fact, the original proof of concept Jumperlesses (called breadWare back then) used an ATMega4809.
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You can make a [UPDI programmer yourself](https://github.com/SpenceKonde/AVR-Guidance/blob/master/UPDI/jtag2updi.md) with just a cheap USB-Serial adapter.
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```
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USB Serial Adapter
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-------------------- To Target device
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DTR| __________________
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Rx |--------------,------------------| UPDI----------------->
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Tx |-------------' .--------| Gnd
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Vcc|---------------------------------| Vcc
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CTS| .` |__________________
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Gnd|--------------------'
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--------------------
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```
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*It's so simple they didn't even need to make the guide an image, just some gloriously retro ASCII art*
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Given that we can already do serial passthrough, you'd think this would just work. We were both mildly surprised when it didn't.
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So he got out a [UPDI Friend](https://www.adafruit.com/product/5879) and compared the output.
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Here's what the Jumperless was putting out (this wasn't working):
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And here's the UPDI Friend's output (this was working):
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*Don't worry about the horzontal scale, they're the same, it's just how the screenshots were taken*
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Note the one with the framing errors is the one that worked. This was extra confusing, until we thought about what "framing" actually means here.
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8N1 (8 data bits, no parity bit, 1 stop bit) is just so common for 99% of things these days that it's easy to forget anything else is ever actually used. Even the logic analyzer forgot about it, hence the framing error.
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It turns out UPDI actually uses 8E2 (8 data bits, 1 even parity bit, 2 stop bits), and once we changed the routable UART to that, UPDI flashing through a Jumperless V5 worked like a charm.
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### The Part That I Didn't Think Was Even Possible
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But then how do we let users change between different configurations / baud rates depending on what the routable UART is connected to?
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After a bunch of digging through the [TinyUSB Library](https://github.com/hathach/tinyusb), I came across this:
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**_What?!_** I can just straight-up **_ask?!_**
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I was thinking I was going to need to write a whole thing to send test data to itself and figure out the baud rate and encoding with some hacky function, but nope, asking works. There's a life lesson in all this, sometimes just politely asking for what you want is the right move.
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So let's write some code that uses these magical functions to check for any config changes from the host side, and then restarts the passthrough side with the same settings.
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Holy crap this made serial passthrough soooo much less finicky. Not only for UDPI, now flashing the Arduino in the header is rock-solid too. This also lets you put an RP2040/RP2350 into boot mode with the 1200 baud "tickle" thing instead of needing to press the button.
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So here's what changing the settings looks like now:
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Yep, you change settings on whatever serial program you're using and they'll be reflected on the Jumperless. What makes this extra clutch is this allows things like [avrdude](https://github.com/avrdudes/avrdude) to do all their serial port magic without any extra setup. And it's really cool to be able to *remove* menu options.
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If you need any of those other flow control signals (DTR, CTS/RTS) that are sometimes used to pull the reset lines low or whatever, you can attach them to any of the routable GPIO and they'll do what they're told.
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So there you have it folks, Jumperless V5 is now even better at being series of tubes. I'm also kind of kicking around the idea of making it a series of bricks as well...
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Let me know whether you think this LEGO thing is a terrible idea on the [Jumperless Discord](https://discord.gg/CKP2chvcUt), [Forums](https://forum.jumperless.org/), [GitHub](https://github.com/Architeuthis-Flux/JumperlessV5), [Twitter/X](https://x.com/arabidsquid), [Bluesky](https://bsky.app/profile/architeuthisflux.bsky.social), [Mastodon](https://hackaday.social/@ArchiteuthisFlux), or in person at Hackaday Supercon 2024.
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Love,
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Kevin
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P.S. Huge thanks to @DerelBims for contributing a lot of the code you see in this update,
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