Did OneWire of DS18B20 sensor fame ever fascinate you in its single-data-line simplicity? If so, then you’ll like PJON (Padded Jittering Operative Network) – a single-wire-compatible protocol for up to 255 devices. One disadvantage is that you need to check up on the bus pretty often, trading hardware complexity for software complexity. Now, this is no longer something for the gate wielders of us to worry about – [Giovanni] tells us that there’s a hardware implementation of PJDL (Padded Jittering Data Link), a PJON-based bus.
This implementation is written in Verilog, and allows you to offload a lot of your low-level PJDL tasks, essentially, giving you a PJDL peripheral for all your inter-processor communication needs. Oh, and as [Giovanni] says, this module has recently been taped out as part of the CROC chip project, an educational SoC project. What’s not to love?
PJON is a fun protocol, soon to be a decade old. We’ve previously covered [Giovanni] use PJON to establish a data link through a pair of LEDs, and it’s nice to see this nifty small-footprint protocol gain that much more of a foothold, now, in our hardware-level projects.
We thank [Giovanni Blu Mitolo] for sharing this with us!
I haven’t seen any bidirectional one wire bus before. I’m pretty sure I’ve heard of them but never seen one in the wild. In fact the only one wire device that I’ve seen is DS18B20 style temperature sensors
It claims speeds of about 2kB/s to 3kB/s, depending on desired range, which makes it about ten times faster than Commodore’s 1541 IEC bus. Not that I’m still bitter or anything…
I see there’s a bitbanged implementation available. They also explicitly reference radio and light-based networking, so this could be useful for very cheap infrared networking, say. I’ll admit to not being thrilled by the fact that PSON™ trademark licensing rules.
Umm, Dallas Onewire, as used by DS18B20, is a bidirectional bus.
It was very popular and likely still is in common use, many bars and restaurants use(d?) Onewire ID tags to allow staff fast logon to POS and if you’ve ever owned a Dell laptop with a genuine charger you’ve used the TO92 or SOT version of those tags.
Should not be too hard to implement with Pi Pico PIOs+DMA…