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Yet Another PCB Version

April 26, 2014

14-04-25 top

I decided to do another PCB for the Olduino. It’s basically the same circuit I’ve been using but laid out properly instead of hand-hacked. I’m hoping to use the new membership card I got from Lee Hart with a 3.2MHZ clock and hopefully I can get the olduino add-on working with a 4 MHZ SPI clock to let it run full speed.  The top of the board is shown below, courtesy of an online gerber viewer at  Mayhew Labs.

The ATmega as usual is the communications to the windows host and also generates the 8 pulses of the SPI clock when requested.  The 74595 is the input shift register – MISR, the CD4021 is the output shift register – MOSR; these are attached to the MISO, MOSI, and SCK positions on the Arduino headers.   The 74374 is a parallel output port that feeds what would be arduino digital pins 3-10.  The red rectangles outline the arduino header rails and the long blue rectangle outlines the 30 pin connector to the membership card below.  The extra six pins are for control signals being brought up.

Believe it or not, I may do one more version this summer. This would be with a 74165 instead of the cd4021 because the 4021 tops out at 2-3 mhz, a smaller avr chip than the atmega, and a slimmer overall form factor. I should be able to prototype the 74165 and attiny on this platform and do another iteration. I could, in principle, have done those changes this round but I prefer to get something that has a high probability of working and iterate from there.

The schematic is below in image file and PDF:
14-04-26 olduino_2.0_v4d

olduino_2.0_v4d PDF

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  1. Looking good Bill! I’m surprised the Olduino hasn’t been on the pages of HaD yet.

    Lots going on in the MC/Olduino world this weekend; what with Lee Hart announcing an updated MC design yesterday that allows for both Ram/Rom + Serial + dual colour Q (status) and new jumper options for mapping memory.

    • Thanks Andrew. I still consider this version clunky. I’m going to do one more in the summer to clean it up and then I’ll publicize it. It’s funny though, this blog gets dozens of views most days from a bunch of different locations so i guess the word gets around.

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