• Time to start documenting the software development for the Raspberry Pi 4 (3).
  • Back ordered semaphores may be available in April!
  • Rebuilding the Pi fan board to make room for the DSI ribbon cable.
  • Updated the sitemap generator software.
  • With Raspberry Pi 4/AdaFruit updates (?) now the library items don't work to support the 16-channel PWM HAT/Bonnets!
  • Excellent help from AdaFruit forum admin. Forced a package update.
  • Updated both TechSmith tools.
  • Back to the fan. Version #2 of the hardware. Need to clean-up the library. I have forgotten how what I did before works.
  • Having read some of the IO Pi Plus HAT documentation, need to do some redesign, move some wires around. 

The IO Pi divides the 32 IO pins into 4 groups of 8 pins. Using 24 pins as inputs for status of the 12 turnouts could be interrupt monitored by connecting 2 or 3 interrupt pins from the IO Pi to 2 or 3 Raspberry Pi GPIO pins with voltage dividers to drop from 5vdc on the IO Pi to 3v3dc on the Raspberry Pi.

On the Raspberry Pi 4 (3) currently 24 of the 28 GPIO pins are in use. Three of the remaining pins (0, 1 & 26) are not broken out on the 16-channel PWM HAT leaving one (pin 4) readily available. 

    1. Could move the 4 traffic monitor LED pins from the PWM HAT to the IO Pi freeing GPIO pins to be interrupt driven on the Raspberry Pi. 2-3 voltage dividers would need to be added somewhere.
    2. On the header board for the Unicorns could bring out the 3 GPIO pins not brought out on the PWM HAT to use as interrupt inputs. There is also room for the 3 needed voltage dividers (6 resistors) and a 3-pin header..