Paolo Amoroso's Journal

I cross-develop CP/M programs on Linux with the Suite8080 assembler and run them on a number of platforms, from software emulators to the Z80-MBC2 computer. But to test the code I use an emulator for Linux called ANSI CP/M Emulator and disk image tool, or just CPM.

CPM is unique in that it reduces development and testing friction. The emulator can execute CP/M programs stored on the Linux file system by passing CP/M executable files as arguments, such as:

$ cpm cpmprog

where cpm is the emulator and cpmprog.com is a .COM file on Linux. In addition, the current Linux directory appears as the A: drive from CP/M, so any .COM files there on Linux can be executed from CP/M like this:

A>cpmprog

Again, cpmprog.com is a .COM file on Linux.

This feature shortens the development cycle, as the emulator can access program files cross-assembled on the same file system it runs on.

Other emulators require copying files to disk images and mounting the images from the emulated environment. And before they can be run on the Z80-MBC2 or other hardware, CP/M programs need to be transferred via XMODEM or other means.

Once a .COM program is tested and debugged, I run it on richer CP/M environments like the z80pack emulator or the Z80-MBC2.

#retrocomputing #cpm

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If you lived through the personal computer revolution of the 1980s, you may have read some books that got you hooked with programming. These works led the reader through the intellectual adventure of using computing to explore interesting problem domains.

Two recent Python books bring back this fascination and excitement with programming, Impractical Python Projects: Playful Programming Activities to Make You Smarter and the sequel Real-World Python: A Hacker's Guide to Solving Problems with Code, both by Lee Vaughan and published by No Starch Press.

They are not Python tutorials or guides. Instead, they present stimulating coding projects for non-programmers who want to use Python for doing experiments, test theories, or simulate natural phenomena. This includes professionals who are not software developers but use programming to solve problems in science and engineering. And, of course, hobbyists.

Exploring and understanding the problem domain is an integral part of the books' projects along with coding. This is unlike typical programming books where the examples are often trivial, have little or no domain depth, and are stripped of everything but the essentials.

The science and engineering Vaughan's books cover include some great projects that match my interest in astronomy and space. For example, Impractical Python Projects has chapters on estimating alien civilizations, simulating a volcano on Jupiter’s moon Io, simulating orbital maneuvers, and stacking planetary images. Real-World Python discusses re-discovering Pluto, plotting the Apollo 8 lunar trajectory, selecting martian landing sites, and detecting exoplanets.

The sample code is straightforward, clear, and hints at how much can be done with little code. Since the books are not language tutorials, they focus on prototyping and exploration rather than building large and maintainable systems.

#Python #books

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Over the three years I ran my discontinued Blogger blog I published 146 posts. In just seven months I published 151 posts on this new blog hosted at Write.as, which drives home the superiority of Write.as as a frictionless blogging platform.

#blogging

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I ported to Intel 8080 Assembly the Z80-MBC2 Z80 code of the led blink demo, assembled it with the Suite8080 assembler, and uploaded the HEX binary to the Z80-MBC2. Instead of printing a message to the console and blinking the User led, the program made the led turn on and the board reset, booting up the default operating system.

I have no tools to debug software that runs on the bare metal. So the next step is to investigate these clues, starting from a comparison of the Z80 and 8080 sources.

#Assembly #z80mbc2 #Suite8080

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The conventional blogging wisdom is to address the readers as you and avoid writing in first person. This is supposedly friendlier and makes the readers feel at the center of attention.

I use you sparingly. For example, when I write how-to or instructional material, ask something, or try to persuade. Most of the times I write in first person. It's a natural way of sharing with fellow tech enthusiasts my direct experience and projects, the steps I take, the thought processes I go through, the setbacks.

There's another reason I rarely address readers as you.

You may come across as a marketing or SEO tool. The insincere intention of pleasing and luring readers to sell something — products, ads, attention — and monetize blogs.

My readers can cut through the BS and know when I feels right.

#blogging

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I'm looking for source code of MS-DOS .COM programs in real-mode 8086 Assembly written in NASM syntax.

Why such weird requirements? I'm learning Assembly programming under MS-DOS and MikeOS, and cross-developing on Linux with NASM. To avoid the complexity of x86 segmentation, I prefer to focus on single-segment programs as I plan to write small applications anyway. So I'd like to study examples of how these programs organize and reference data and code.

Despite the long history and influence of MS-DOS, finding .COM code is proving unexpectedly hard.

Googling doesn't turn up much. I solicited recommendations on comp.os.ms.dos.programmer, comp.lang.asm.x86, the NASM forum, and Mastodon but, aside from a lot of engagement and interest (and the occasional suggestion I change my mind and target Windows), I got few resources.

#Assembly #MSDOS #retrocomputing #x86

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My post on why I use a Chromebox was shared on Hacker News and got enough upvotes to receive more than 4,000 views over a day. The feedback in the comments made me realize I didn't explain why I use chromeOS instead of Linux, so here goes.

I did use various Linux distros from the mid 1990s until switching to chromeOS, but I got exasperated with maintenance.

Device driver support was suboptimal. System updates would often break something and throw me to the console, forcing to waste days to troubleshoot and fix whatever broke and restore X. These issues were so frequent I ended up deferring to apply system updates, trading features and fixes for stability.

I had enough with Linux maintenance, realized I was living in Chrome anyway, didn't mind Google, and gave chromeOS a try. Seven years and four chromeOS devices later, I never had a single system update issue. And maintenance simply disappeared.

For years I used also Windows and Mac OS X but I liked Linux — and later chromeOS — much more.

#chromeOS #Linux

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Chromebooks are mainstream but many people don’t grok Chromeboxes.

Some wonder what’s the point of Chromeboxes and what to use them for, especially high-end units. People seem to assume Chromeboxes are good only as kiosks or for who knows what uncommon use-case.

This is the main unit of my ASUS Chromebox 3:

I chose a Chromebox because I nearly never need to move my primary desktop device. And I want the most high-end unit I can get my hands on to do the same stuff cheap Chromebooks can do, but faster.

Let me elaborate.

First off, in 2015 I switched to using exclusively chromeOS on the desktop and ditched traditional desktop operating systems such as Linux or Windows.

Therefore, for me the choice is among the form factors of chromeOS desktop devices: Chromebook (laptop), Chromebox (fixed desktop system), or Chromebase (think iMac for chromeOS).

I went with a Chromebox as my daily driver because I work with it at the same desk 99.999% of the time. Since I nearly never need to move the device, not even to a different room or chair, I want the best experience with a large monitor, a full-size keyboard, a mouse, and wired Ethernet. I could plug these peripherals into a Chromebook but it would introduce friction, take up additional desk space, and cost more.

Here's the workstation of my ASUS Chromebox 3.

I got the most high-end Chromebox available at the time I researched it, i.e. an Intel CORE i7 ASUS Chromebox 3 with 16 GB RAM and 256 GB storage. Why? To run exactly the same software that works on cheap Chromebooks, but with a snappier and more responsive experience. If you're old enough to remember MS-DOS, it’s the same reason people got 80386 PCs when the same software ran just fine on 8088 PCs.

Why not a Chromebase? Because I want to be able to upgrade different parts of the system separately, such as changing only the monitor.

As for software, I use mostly web apps and they work great on chromeOS as this is the use case the platform was designed for. Installing Android apps on the Chromebox fills a few gaps in my needs for which no web alternatives are available. Crostini Linux is invaluable in running specific and niche software.

I happen to have a Chromebook too, a Lenovo Yoga N26. I use it for experimenting with Chrome OS and on the — very rare — occasion I need the mobility of a laptop.

#chromeOS

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I've always worked in astronomy and space outreach and education. But one of my assignments led to an unusual experience in a completely different field, art.

In 2018 I was hired for an art project at Fondazione Prada, precisely because of my astronomy background.

Fondazione Prada (Prada foundation) is a contemporary art museum and cultural institution in Milan, Italy, where I live. It's a unique and intriguing place, especially for someone like me with no art background. What impressed me most were the architecture and the insightful conversations I had with staff members, such as the room guardians who are usually art or design students.

Between August, 11 and October, 22, 2018 Fondazione Prada run a temporary exhibition by Brazillian artist Laura Lima, Slight Agitation 4/4. It featured an impressive series of room-sized installations, including one named The Telescope. It was a giant scaffholding structure with a lecture space and an actual small telescope.

My job was to do daily performances inside the structure, i.e. ordinary astronomy lectures. Laura Lima advised me to focus and geek out on astronomy, not art.

I talked about the Moon, Mars and the planets, comets, space exploration, and more. This is the whiteboard I used, with my doodles after a lecture on comets and meteors.

It was a fun and unique experience the many visitors who attended the lectures seemed to appreciate. I didn't anticipate so much interest and questions in a context where people didn't expect to stumble upon science.

Prada Foundation published a video that shows Slight Agitation 4/4 and the structure where I performed. I'm the guy with sparse hair and glasses handling the telescope at 00:45 and 03:08, and lecturing at the whiteboard at 02:47.

#astronomy

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One of the Z80-MBC2 boot menu options, iLoad, allows uploading an executable program in Intel HEX format. This is cool because it enables running code on the bare metal with no operating system, such as a resident monitor or software that directly accesses the hardware.

To test iLoad I uploaded and run a demo to the Z80-MBC2, a Z80 Assembly program that prints a message to the console and blinks the board's User LED.

The source file, Blink demo Z80-MBC2.asm, is included in the sources of the Z80-MBC2 firmware in directory src. I assembled the program with the zasm Z80 assembler and converted it to HEX format with the bin2hex tool that comes with the z80pack Z80 emulator.

The screenshot shows the steps for uploading the demo to the Z80-MBC2 and running it. It's a Minicom session under Crostini Linux on my Chromebox.

First off, I brought up the Z80-MBC2 boot menu. After selecting the iLoad option, the Z80-MBC2 waited for the file transfer to start.

Next, in Minicom I executed the Paste file command (activated by the Ctrl+A Y keystroke), which reads an ASCII file and sends its contents as if it were typed in, and selected the program file blink.hex. A few seconds later the message Z80-MBC2 User led blink demo running... appeared on the console and the board's User led started blinking.

I completed the process successfully only after tweaking the transmission parameters.

The Z80-MBC2 developer notes the board's serial port can't handle high-speed data transfers, and advises to set a 50-90 ms newline transmission delay in the settings of the terminal emulator used for the transfer.

In Minicon I set the delay with the Newline Tx delay (Ctrl+A T D) option. But with my setup iLoad transfers abort even with delays up to 150 ms, causing the Z80-MBC2 to display a checksum error and halt.

To overcome the issue I set a character transmission delay of at least 5 ms with the Character Tx delay option (Ctrl+a T F).

#z80mbc2 #z80 #sbc

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