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Marko Mäkelä wrote the C2N232 firmware in
machine language. Everything is driven by interrupt requests, and
only 4 bytes of the 128-byte memory is reserved for the execution
stack. The rest, 124 bytes, implements the RS-232 reception
The firmware can be compiled to executable binary code with GNU
Binutils, and it can be uploaded to the C2N232 device with AVRDUDE. Many RS-232
interfaces for USB are
ridden with bugs that prevent their use in firmware programming. Even
properly working interfaces, such as those based on the Prolific
PL-2303, are very slow, about 10 bytes per second. Built-in RS-232
interfaces and are about ten times faster, and they work for sure.
- Updated firmware version 5: source code and compiled code for the
C2N232 (AT90S2313, 8 MHz) and the C2N232I (ATtiny2313, 18,432 MHz).
This is the first released firmware for the C2N232I. Please read
avrdude.txt in the archive.
- Firmware version 5: source code and compiled code. Supports the
cassette motor control signal.
- Source code of firmware versions 1..4 and compiled code of
firmware version 4
- Firmware version 1 source code for avra
- c2n232i.s, c2n232i.txt
- From June to December 2003, I developed a Commodore serial bus
connection for the C2N232. It does successfully emulate a
peripheral, such as a disk drive, but for some reason, it fails to
work as a controller, i.e., to send commands to a disk drive. You
can have a look at the firmware and short notes on how to test it.
- The wire protocol of the C2N232 serial line
- Timing diagrams of the custom transfer protocol