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Z80-MBC2
The Z80-MBC2 combines a Z80 and an ATMEGA32A to provide a CP/m capable computing environment. It features a SD card bootloader which makes running Collapse OS on it rather simple.
Recipe
In this recipe, we're going to run Collapse OS on the Z80-MBC2, interfacing through its serial port. We're going to use the MBC's API to implement BLK on the SD card.
Gathering parts
- A Z80-MBC2 computer with its SD card module and a properly flashed “IOS” on the ATMega32A.
- A FTDI-to-TTL cable to connect to the serial port.
Building the binary
Running make will yield os.bin which is what we want.
Running on the Z80-MBC2
Mount the SD card on your modern computer and copy os.bin as autoboot.bin,
overwriting the binary that was previously there.
We also have to copy the blkfs over. This is done by using IOS’ drive system.
Each DSxNyy.DSK file on the card is a drive, each drive has 512 track of 32
sectors of 512 bytes, so one drive is plenty for our needs. Collapse OS
hardcodes drive 0.
Each drive is part of a set. IOS theoretically supports up to 10 sets, but the
binary shipped by default only accepts 4. You have to overwrite an existing set.
I used set 3. So, copy blkfs to file DS3N00.DSK. If you want, you can change
the name of the set by changing the contents of DS3NAM.DAT.
Put back the SD card in the Z80-MBC2 and power it up by connecting the FTDI adapter to it (red: VCC, black: GND, green: TX, white: RX).
The FTDI adapter will show up as something like ttyUSB0 (or ttyU0 on
OpenBSD). Connect to it with screen or cu or whatever you like. Baud rate of
the Z80-MBC2 appears to be hardcoded to 115200.
Then, enable IOS program selection by holding RESET and USER at the same time, wait 2 seconds, releasing RESET, wait 2 seconds, releasing USER. You should then be given a 1-8 choice.
You begin by selecting the proper disk set, which is through choice 8, then you select the Autoboot binary through choice 4.
You are now in Collapse OS.