Re:Jacdac Plug-and-Play for Microcontrollers
by gbraad on Wednesday March 16, 2022 @10:38AM
(#30699382)
It was developed IIRC by an intern as part of his thesis and included in the microbit tooling on makecode. After this it got more standardized, but they went to a less obvious connector (Kittenbot came with a standard jack) and now they describe a custom plug. This increased the barrier of entrance and building came less appealing to me.
Re:Jacdac Plug-and-Play for Microcontrollers
by mmoskal on Wednesday March 16, 2022 @11:33AM
(#30700075)
The main issue with audio jack cables is that they are not designed to carry much power (Jacdac cables are rated at 1A). You get different voltage drop depending on what cable user bought at the gas station. This is a problem is you want to run a small servo or even a few neopixels on a module.
Another issue is that the connector often short while plugging-in and out which may cut the power to your entire bus, resetting everything. Not a great end-user experience. There is also a risk users will plug Jacdac to their headphones, possibly burning them.
Re:Jacdac Plug-and-Play for Microcontrollers
by joezydeco on Wednesday March 16, 2022 @11:06AM
(#30699708)
Yeah it totally has that 'quickly-launched-short-lived summer intern project' vibe to it which is fine but is something I'd typically expect out of Google, but not Microsoft.
Re:Jacdac Plug-and-Play for Microcontrollers
by mmoskal on Wednesday March 16, 2022 @11:22AM
(#30699923)
Indeed, if you know how to design a custom PCB, have it made, and write embedded software, then Jacdac might be an overkill for you.
The Qwiic cables have to be really short (Jacdac cables can be a few meters) and are not designed for easy plug-in and out thousands of times. Also, the I2C devices are not standardized meaning you need a new driver in your software environment for every single accelerometer. Finally, I2C doesn't let you have multiple instances of the same device because of address collisions.
Re:Jacdac Plug-and-Play for Microcontrollers
by joezydeco on Wednesday March 16, 2022 @12:31PM
(#30700891)
But doesn't Jacdac require PCB customization as well to make that edge connector work?
Re:Jacdac Plug-and-Play for Microcontrollers
by mmoskal on Wednesday March 16, 2022 @01:13PM
(#30701439)
Eventually, you'll be able to buy Jacdac modules, brains, and cables.
Re:Jacdac Plug-and-Play for Microcontrollers
by camtarn on Wednesday March 16, 2022 @10:59AM
(#30699633)
Yeah. Something like a standard set of protocols on top of an existing peer-to-peer bus, with a good set of supporting libraries, would have been great. I love the idea of service advertising and standard service APIs.
https://web.archive.org/web/20191130155328/https://jacdac.or...
I worked with a similar single-wire protocol when working with a large German appliance maker. This looks pretty close to the same idea, they even used PCB edge connectors like this to save a few pennies.
I'll just add that getting the software and hardware right is a lot trickier than it looks. Bus arbitration and collision recovery at the hardware level isn't always the easiest when working with low speed microcontrollers. And, by the time you have it all working, you've reinvented CANBUS but without the differential signalling so you need to keep the cables short.
And all of this is supposed to fit on a single 'cute' board with a pushbutton or tricolor LED? Hardware overkill.
It probably has some use in the hobbyist sector, I'd love to see Sparkfun or Lady Ada pick it up but they're very smart groups and have their own direction with things like Qwiic (which is just I2C, something already on a lot of MCUs in hardware) The proprietary connector, fixed to 3 pins only, is a huge turnoff too. I can get a lot more mileage out of putting FTDI parts on each side of a board and using USB-C patch cords I bought at the gas station.