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Teensy-based PDI5 programmer

2011/07/12

I’m preparing to radically scale out my product development, which means a number of things.  First, I’ve ordered parts to populate 2 more of the “OctoPDI5” boards, so I can scale out to a total of 24 units under development at the same time, all of them electrically isolated from each other and the host computer.  I’ve also got an inexpensive 1920×1080 monitor on the way that will have enough room for me to actually put 24 copies of by debugging console on it in pivot mode.  However, I’ve still got to program/debug the controller board for this whole mess.  So far I haven’t had enough stations active at the same time to make me hit the 8-port limit on the OctoPDI5.  However, with 24 stations and 3 OctoPDI5’s, I’m going to need another programmer…

Luckily I have a Teensy++ sitting on my desk, which I haven’t had a chance to do much with yet besides play with the loader and core examples.  It’s nominally got all the stuff I need to pull this off, though before I actually connect it to anything I’ll need to alter it to run on 3.3V lest it blow out my port controller with 5V…

The software stack porting turns out to be quite trivial, because of the way I’ve set up all the code for the existing PDI5-related boards.  Basically I’ve built a rough object-oriented system for the various “streams” such as USARTs and the STK500V2 engine.  A little bit of hacking gave me both an “avrmega” standard USART module (though it’s hard-coded for USART1 so far; I’ll need to enhance it to run on “any” AVR mega, especially the one with more than one…) and a “USART” that uses PJRC’s usb_serial code.  A little more code gives me the “iosmux” mainloop that multiplexes the serial and stk500v2 streams through the upstream.  Some quick tweaks to my host-side software so it handles the /dev/ttyACM0 path instead of /dev/ttyUSB0, and I’ve got the basic ability to send a text substream out to hardware.

The next step will be porting the PDI physical layer to the “avrmega” type, and shuffling the pdi5 code around so it’s not hardcoded to the Xmega PHY.  Neither of those will be particularly difficult.  At that point I’ll be able to hook up a PDI5 cable (USB micro-B) to the Teensy and my port controller, and I’ll have a nifty single-port version of the OctoPDI5 (albeit without isolation in this form).

At some point in the future I hope to implement an ARM SWD interface in the same style as PDI5, using the same cable, connector, and pinout.  If all goes well I should be able to run this on a Teensy as well, which means I might have a particularly killer ARM programming interface at some point ;-)

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