psfSep 4, 2025
Current state of the #MailStation homebrew software: a singleline text field for user input, and a much larger multiline text field for program output. So we now have a terminal-like interface we can use as a basis for writing command-line software.
Show threadpsfSep 4, 2025
Most of my development so far has used the community-created JsMailStation emulator, but it's a good idea to test on real hardware occasionally. For me, that means keying the program into the #MailStation's built-in hex editor. It still fits in less than 256 bytes, so the data entry isn't as time consuming as it might seem... yet.
Show threadpsfSep 4, 2025
Incongruously for a #z80 powered device, the #MailStation is heavily GUI based. There isn't a putc function, or even a fixed-width font, in the firmware. Instead, a windowing toolkit and a selection of widgets are provided, and loadable apps are expected to be event-driven. Each app supplies a main event handler function responding to incoming signals such as init, draw, and keydown. Apps don't take over the whole system as typical on single tasking retrocomputers. While the Mailstation doesn't do true multitasking, (or even #HP200LX-like switching between paused apps!), the event-driven software architecture is helpful for battery life, as the CPU can spend most of its time halted waiting for interrupts.
Show threadpsfSep 6, 2025
After lots of invisible optimization work, I've saved enough space that my new #MailStation app can display its name and icon in the app launcher.
Show threadpsfSep 7, 2025

I have now written a #z80 machine code monitor for the #MailStation. The command set is very influenced by WozMon, but unlike #Woz I haven't managed to fit it in 256 bytes (yet...)

So now, in the strictest sense of the word, I have a #repl on this thing!

(While there was already a built-in hex editor, it was not suited to interactive use. A reboot was necessary to test changes, and it was restricted to writing dataflash, which has a limited number of write cycles.)

Show threadpsfSep 9, 2025

PsfMon, my #z80 machine code monitor, is now running on my real #MailStation!

I optimized it from its original size of 332 bytes to 255 bytes, snugly fitting in one 256 byte page of dataflash. The gui "terminal emulator" takes another 256 byte page. This provides a self contained 512 byte development tool.

Command set - similar to #WozMon:

8000 - View byte at address 8000
8010,801f - View 16 bytes at address 8010
,803f - View from next address (8020) to 803f
8040>de ad - Place bytes de ad starting at 8040
>be ef - Place bytes be ef next (at 8042)
8000r - Execute code at address 8000

Anyway, here it is displaying 128 bytes of its own code.

Show threadpsfSep 13, 2025
Learning that software development using a hex machine code monitor involves far more pen & paper work than computer work.
Show threadEric Carroll

@psf do enough coding in raw machine language and you won't need pen and paper.

I coded straight to 6502 and 8085 hex in the Time Before Assemblers. Then I wrote an assembler and never looked back.

Mind you I knew someone who insisted on coding in hex editor straight to machine language. He really objected to changing to an assembler. His code was a mass of jump instructions patching in changes (because hex editor).

This is why god invented cross compilers.

Sep 13, 2025 at 6:45pmWeb