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Comment by SV_BubbleTime | Hacker News Reader

So he remade CAN without requiring a specific physical layer?

This jumps around a bit between the transport and phy a bit, I guess I didn’t really get where the special sauce is. I also never saw a kbps number.

There is potential I would have use for such a thing I guess. Although LIN works pretty well over 1wire and is built in to most UARTs now.

It makes me cautious when I read these things and don’t see specific talk about what hardware module is expected to do the work. Yea, they got two wire twisted pair distance, is that using a specific transceiver? Does that hook to a USART or CCP or SPI? It sounded async because of the longer bits as start of frame, but bit banging and capture/compare kinda sucks.... IDK maybe it addresses this all and I missed it.

What I didn’t miss is he is selling a book at the end.

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Here you can find the implementation of PJDL used by Jack Anderson to determine the maximum range:

https://github.com/gioblu/PJON/tree/master/src/strategies/So...

All devices listed in the compatibility section are able to communicate over a twisted pair with no additional hardware, as Fred well noted, you just need one wire and connect directly the IO pins. And up to 255 devices can share the same twisted pair.

As you can read in Video Camera Control Jack just used two arduinos, 2km of wiring within his university's network and a couple of pull-down resistors. The protocol works even when the human body is used as a conductor as shows the gif present in the article.

On social compare someone made this: https://socialcompare.com/en/comparison/comparison-of-networ...

I think the comparison between PJON and LIN there is revealing. As you can see LIN handles up to 16 devices, it is master-slave and has a range of 40, with a complex front-end at a relatively high voltage.

PJON is free for use, it is all open-source. We do sell products to fund the development of the project.

Thanks, that helps.

I had to check quick at a gas station and post this.

For the most part, I took away 27kbps, and it seems the intention is software bit bang.

Sure, it’s not master/slave like LIN, and with an arbitration scheme more like CAN. But, without hardware codec, DMA buffering and interrupts, I feel it’s a lot less useful to me as my embedded projects are already pushing their limits with hardware communication.

Still, while it’s not good for me, I do see utility in a bit bang format for LED, IR, simple RF, etc. This makes sense and seems well thought out.

No worries, for sure the SoftwareBitBang implementation is not designed to stream digital audio or video at high speed but it is handy for many to move few bytes from sensors in a local network that can be built very quickly and at a low cost.

Have a nice Christmas :)

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