Tuesday, April 22, 2014

Minima - CPU Module Mods - PLus

After chatting with my friend, Jeff - KO7M, I decided to again modify the next Revision of my Minima Controller. Jeff has pointed out that a new raw ATmega328 processor does not have a bootloader.

I guess I knew that already, but I thought that I could use the TxRx pins to download a bootloader similar to downloading an Arduino Sketch. I was wrong.

More research is/was obviously needed.

REV04 of my Minima Control Module
The Backside
The latest addition to my Minima Module Mods is a JTAG connector, which will be used to download the Arduino Bootloader, or other raw mode programs (or sketches). The JTAG connector is under the "locally" mounted LCD display (left of center), but the display will be un-plugged during the JTAG use, because the JTAG and the LCD uses some of the same processor pins. I will have to check that the JTAG connector pins will not interfere with the mounted LCD board.

Once the ATmega328 programmed with the bootloader, the display will be re-installed, and then normal sketch programming will be done via the Prop-Plug TxRx header (lower right).

My previous modifications included; Consolidation of several individual headers into a single AUX-CTL header (lower left), Remove the Minima schematic programming components which will be replaced with a Prop-Plug header. I have also added my own version of EMI suppression by adding 1nF caps to each board edge header pins.

This board is getting complex enough that I am considering having it professionally manufacture, it is about 6.6 square inches and will cost a few bucks, but it now has about 65 via's (which are not exactly fun to do on a Homebrew board). I may still create a prototype board via Toner Transfer, but it will take some time/work.

The goal for this board is to be compatible (but more flexible) with the Farhan Minima Transceiver Project. I also plan to use this board with/for other Test LAB projects.

More project info to follow .  .  .


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