Monday, June 1, 2020

RC2020/04 Finale and Wrap-up

After getting OS9 to boot to the shell on my CMS 9619 SBC, I was hopeful to get the DriveWire module working to load in disk images in a more intuitive way. I don't have an extra RS232 to USB adapter currently available to me, so I tried using a USB to TTL level serial adapter on the board's peripheral port connected to the MC6821 PIA. Using the DriveWire module intended for use with the Tandy CoCo's serial "bit-banger" port (also connected to a MC6821 PIA), I was hopeful that I could get things running. Unfortunately, I am pretty sure I am having some sort of baud rate mis-match. The module issues a single character (probably indicating an INIT), then everything is stuck. I am not totally sure what baud rate I should use since my board is running at 2 MHz, compared the the Coco's 0.89 MHz. I think that is probably a lost cause without significant modifications to the timing in the software. (Actually, 57600*(2/0.895) ≈ 128000, a standard baud rate. I will give this a try...)

Once I get my other RS232 to USB adapter, I should just be able to run it off of the serial port, without any bit-banging related timing issues.

RC2020/04 Wrap-up

So, I am fairly happy with my progress this RetroChallenge, despite having to move to a new house. The extra month certainly helped. I was able to:

  1. Make some hardware modifications on my CMS 9619 to get enough on-board RAM to run OS9 (Part 1, Part 2)
  2. Get OS9 booted to the shell on the CMS 9619
  3. Order my EXORbus backplane card design (Part 1, Part 2).

Once I get the rest of my supplies out of storage, I will get some of the backplanes on tindie for purchase.

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