Sillycony : because retro-computing is fun!
After having imagined several solutions to obtain an acceptable keyboard for the µPF - 2, I ended up using key caps which it is possible to label:
For the moment I have not printed the labels of the keys in color, it would have been nicer, but the result is quite practical. This keyboard has nothing to do with what the original kit offers : https://www.kswichit.com/Z80/Z80.html.
New step in the production of the µPF--1 compatible board: the use of the PIO of the IOM expansion.
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| https://fjkraan.home.xs4all.nl/comp/mpf1 |
In fact, I picked up this 'supposedly' new extension a few years ago on eBay for a low price. Obviously, when it was powered, the general voltage was only 4.6V.
One of the RS232 drivers was problematic. So I removed it from the board and also changed the 5V regulator because the 7805 regulator which undoubtedly heated, only delivered 4.8V. The 5V restored, I connected the board to the µPF--2 and after some modifications of a small test program, I was able to run the famous basic 'Hello World' : the lighting of the three leds.
A few weeks ago, I talked about Sergey Kiselev's MSX2 compatible processor board project and the choice I made not to build the keyboard for reasons of overall system cost.
A small additional check was carried out to verify that this adapter board fits correctly on the OMEGA board:
However, for some time I received a Carnivor cartridge to allow me to copy programs or games to it and finally test the proper functioning of the OMEGA board:
At least I have already been able to test that this cartridge fits correctly into the connectors of the OMEGA:
I may also have to find a joystick for this machine. Otherwise it will be difficult for me to really test the games ...
Since a few months, I have been in the process of recreating the well-known µPF--1 microprocessor kit :
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| Wilipedia. |
I also added some possibilities and modified the software system accordingly. This allowed me to recreate the kit on a standard FPGA board:
This new system works very well, but on the one hand the FPGA board used is generic and not really suitable for the intended use. This FPGA board also does not offer a USB serial port and the expansion port is not suitable for setting up Z80 type extensions.
So I decided to recreate a system based on an FPGA. After several attempts and configurations considered, I arrived at this system:
Implementing an FPGA is a bit tricky, so I went with a pre-made FPGA board. Going through this type of configuration removes some of the implementation difficulties, and as a bonus, allows me to offer a more 'powerful' FPGA than the circuit originally planned.
The result remains compact and suitable for intensive use. Note also that this system can be used for something completely different than the recreation of the µPF--1 kit since it has 5V compatible serial and parallel inputs / outputs, a 2x16 LCD display in addition to the eight 7-segment displays.
After shipping the design files, I received the printed circuit board. The first thing I did was to see if the FPGA module can be correctly inserted:
Since my last post about this Easy Z80 board, I installed the integrated circuits in 10MHz version. And that changes everything. At this frequency of 10 MHz, the system is very responsive and becomes very pleasant to use.
Hum... The first time I order a Zilog 10MHz CPU, SIO and CTC directly from Mouser. Brand new and all manufactured in 2020! My first contact with the Z80 was in 1987 with the µPF1+. Wow! And now, 34 years later, a real CP / M system version 2.2:
In summary, this system has a read-only storage unit including the CP / M system plus some necessary utilities. 384K writable storage space is available for downloading external applications. In addition, two communication ports are available in the 115200 Bauds version.
Note that the RAM storage space is backed up by an external battery. The system has an extension bus but unfortunately no I / O port. It's a bit regrettable. So how to test this system?
So I decided to check if I could create the same type of app that I created earlier using a Color Maximite 2 board. This consisted in using the temperature sensor of the expansion board that I created for the Colour Maximite 2 and sending the information to a French Minitel:
It works perfectly with the Coulour Maximite 2. As the Easy Z80 board does not have an I / O port, I therefore decided to recover the temperature from Maximite and send it to the Minitel using Easy Z80. Obviously, this application may seem 'without interest', except that it allows to implement the entire development chain around CP / M.
The development system used is the Z88dk kit : https://github.com/z88dk/z88dk
Nothing more than this kit is necessary except a little knowledge of C and assembly language.
The principle of the application consists in sending the home page from the Easy Z80 SRAM disk to the Minitel, then retrieving the temperature via the serial link coming from the Maximite 2, and sending this information to the Minitel.
The only difficulty of this project is to use the second communication port of Easy Z80 in configuration 1200, E, 7, 1. This is not particularly obvious because the system is designed to operate from at 115200 Bauds. Fortunately, it is planned to be able to use the CTC present on Easy Z80 to generate the clock to the UARTS.
It is therefore necessary to connect the output of channel 2 of the CTC to the channel 2 clock of the SIO. This connection is available on the printed circuit board. It is enough to connect it with a small soldered wire after having cut the original connection.
Once this intervention is done, it is necessary to write a few lines of assembler to configure the CTC and the SIO. Do not forget to remove the RS232 converter U8 from the board because Minitel uses TTL signals.
Finally, the source code is simple and easy to understand:
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71 | //
// Ressources :
//
// https://www.seasip.info/Cpm/bdos.html
// https://github.com/wwarthen/RomWBW
// https://github.com/z88dk/z88dk/wiki/Platform---CPM
// http://www.z80.info/zip/um0081.pdf
// https://pila.fr/wordpress/?p=361
// https://www.goto10.fr/minitel/specifications/stum1b.pdf
//
// Compilation : zcc +cpm -lm -o main.com main.c
//
#include <stdio.h>
int main()
{
FILE *fp;
int Data;
unsigned char Index, Misc ;
// Start application
printf("Starting the Minitel application\n");
// Configure the SIO chanel B for 7, E, 1 & NOT CTS ctrl
#asm
PUSH AF
LD A, 0x33 ; PTR WR3
OUT(0x83), A ; ACESS WR3
LD A, 0x41 ; 7 bits RX, NO CTS, RX enable
OUT(0x83), A ; WRITE WR3
LD A, 0x34 ; PTR WR4
OUT(0x83), A ; ACESS WR4
LD A, 0x47 ; E parity, 1 stop
OUT(0x83), A ; WRITE WR4
LD A, 0x35 ; PTR WR5
OUT(0x83), A ; ACESS WR5
LD A, 0x28 ; 7 bits TX
OUT(0x83), A ; WRITE WR5
POP AF
#endasm
// Configure the Com port n#2 baudrate (CTC) at 1200 for the Minitel
#asm
PUSH AF
LD A, 0x47 ; Counter mode
OUT(0x89), A ; Control Word
LD A, 0x60 ; Counter value for 1200 bauds
OUT(0x89), A ; Counter Word
POP AF
#endasm
// Opening the Minitel Home page
fp = fopen("Home.dat", "r");
if (fp == NULL) {
printf("Error opening Home.dat");
return 0; }
// Send the Home page to the Minitel
Data = fgetc(fp);
while ( Data != EOF ) {
bdos(4, Data );
Data = fgetc(fp); }
// Infinite loop
while (1) {
// Print the 3 char for the display coordinate +
// the 5 char from the Colour Maximite II temperature
// formatted as : 12.55
// So, 8 char to relay
for ( Index = 8; Index; Index-- ) {
Data = bdos(3, Misc);
bdos(4, Data ); } }
// Close the Home page file
fclose(fp);
// End main
return 0;
}
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Note also that CP / M offers 'services' in the form of a generic call by providing some information. This interface is provided in the form of the 'bdos ()' function and is used here to communicate with the communication port # 2.
And the result:
Conclusion: this CP / M board is really very pleasant to use and program with the Z88dk kit. It has an RC2014 type connector for the connection of various extensions. It could be interesting to install a PPI8255 or a Zilog PIO there.
RESSOURCES :
Yes, what reason would there be to use CP/M in 2021? The reason could be, because...!
There can be a multitude of reasons why we might be tempted to discover something other than the boring soup we are served all day long, the digital world : in fact 'shits' for everyone, and huge profits for a few!
And why not take ownership of the tool and have it do something else? Obviously, you probably won't be able to use these simple systems for typing your new bestseller, listening to music, send the latest information of your exciting life to the whole earth or watching series. But there might be more things you can do that you can't do with your MAC or PC.
For that, a system must be simple and easy to use while being inexpensive. At the beginnings of the democratization of computing, in the early 80s, one of the flagship microprocessors was the Z80 in normal (2,5MHz) version or 'A' (4MHz) version and the dream version 'B' (6MHz).
At that time, there was an operating system for this type of processor, the CP/M, called CP/M 80 when a version was developed for the first IBM PC and named CP/M 86, which later became the Microsoft DOS.
At the beginning of the 90s, I had recovered a CP/M 80 machine from a company which had switched to PC/DOS. Unfortunately, I no longer own this machine but this is what it looked like:
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| Wikipedia |
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| Wikipedia |
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| https://github.com/skiselev/easy_z80 |
