Despite having 2 weeks for this, I haven’t actually completed anything notable; So I’m just going to post some WIP images of a PCB I’ve designed to do general purpose programming (Generally jtag, but also AVR)
I’ve been working out the concepts in software using the modified USB stick (as I mentioned previously) but just haven’t had enough time to allocate to it yet. Soon, though.
This design is pretty simple; I have the microcontroller (ATMega32U2), a RGB LED, switch, and crystal – Then around that I am building a set of voltage level translation circuits for the jtag signals, and for additional inputs, outputs, and “pump” signals (which can strongly connect to a target’s V+ level, and drive a significant amount of current)
I’m including the JTAG interfaces I use commonly on the board, and I have another additional “expansion” slot which I’ll be building new boards for to connect to yet other interfaces
Schematic done, decided on a rough layout and started placing parts.
I got the core signals routed, and routed the level shifted jtag signals around the board, connecting to the side connectors as they go.
Added most of the other level shifting signals
And now the design is essentially complete!
Added ground planes, and vias to keep them well connected / allow plenty of return paths.
At this point I thought I was done…. Only, oops, I connected the top 3 headers backwards; I had gone off of the pinout of the socket they plug into. Fortunately I noticed this before trying to produce the board :)
Ahh, now they’re correct.
So I’m having this board produced pretty soon and will write up more on JTAG once I have done some stuff with this.
In other news I’m taking a vacation in about 2 weeks! No, I’m not going anywhere interesting, just visiting family, but perhaps I’ll have something fun to write about by then :) I certainly have plenty of things I want to do!