BBC Micro Serial ULA.

[Becky]

The serial ula, mine is missing. There's a place down in Sussex which has them on the shelf for about £30. I wasn't sure if that was a fair price. Maybe it is, I really don't know. I'm not worried about the tape interface, but I would like to have the serial port working. Are these hard to come by?

[cmorley]

Try contacing Mark (Haysman) at Retroclinic. He is on the forum but better email him directly or message him through the Facebook Acorn group.

edit: The serial on a model B is excellent. I can reliably get 76k8 baud to a FTDI RS232 adapter ... in your face 19200 baud Archimedes

[Becky]

Try contacing Mark (Haysman) at Retroclinic. He is on the forum but better email him directly or message him through the Facebook Acorn group.

edit: The serial on a model B is excellent. I can reliably get 76k8 baud to a FTDI RS232 adapter ... in your face 19200 baud Archimedes

I'll contact Mark After Christmas. I quite fancy playing with a terminal. I fancy logging into my Linux PC with it. I suppose that's just one of those things about retro computing, doing something just because you can. Is 76k8 baud shorthand for 76800 baud? If so that is amazing. I bet your leads are well made!

[cmorley]

I bet your leads are well made!

Nope. A 10m cable I made BITD with some random spare cable my father had hanging around, a 25pin-9pin extension lead and a Startech USB adapter.

IIRC at 76800 you've ~260 CPU cycles between bytes coming in... use them wisely!

[Alan00]

I have a BBC with a faulty serial ULA, I only use 1 baud rate 9600 so I made a small PCB made with a 614.4khz resonator and 74LS04 to genterate a 9600 baud clock. I couldn't get it to work so I decided to use the 1MHz clock on main board and programmed the esp-01 to use 15625 baud as it's default and it worked. I decided to try the 2MHz clock that is used by the ULA and set the esp-01 baud rate to 31250 and it also worked with no problem. It's ideal if you want use Telstar and BBS sites on the internet. The curcuit is very simple with a 3.3V regulator and 2 resistors.

[Becky]

I have a BBC with a faulty serial ULA, I only use 1 baud rate 9600 so I made a small PCB made with a 614.4khz resonator and 74LS04 to genterate a 9600 baud clock. I couldn't get it to work so I decided to use the 1MHz clock on main board and programmed the esp-01 to use 15625 baud as it's default and it worked. I decided to try the 2MHz clock that is used by the ULA and set the esp-01 baud rate to 31250 and it also worked with no problem. It's ideal if you want use Telstar and BBS sites on the internet. The curcuit is very simple with a 3.3V regulator and 2 resistors.

31250 baud is amazing! All I'm looking for at the moment is to make my serial port work and then pick up a Beeb-RS232 cable so I can play with it. Thought it would be fun to access my Linux PC from a terminal on the Beeb and vice versa. No practical reason, just a good old retro-computing "why not"

[Alan00]

I have connected a BBC to a Raspberry Pi, you need to setup telnet up on you Pi on port 22, not SSH.
I use commstar on the BBC and with the esp-01 setup as a virtual modem I type ATDT10.1.1.27:22
Commstar does not work as a ANSI terminal so you can't use nano to edit a program.

[Becky]

I have connected a BBC to a Raspberry Pi, you need to setup telnet up on you Pi on port 22, not SSH.
I use commstar on the BBC and with the esp-01 setup as a virtual modem I type ATDT10.1.1.27:22
Commstar does not work as a ANSI terminal so you can't use nano to edit a program.

Good to know. Cheers.

[Alan00]

My new serial ULA replacment PCB's arrived from China over Christmas, no more sharing 1 serial ULA between my machines.

I have been testing it and all works well at 15625 baud but at 31250 baud I get the odd dropped charactor when accessing BBS sites no problems with Telstar at either baud rate.
I found the Raspberry Pi I set up telnet and have no problems at 15625 baud.

It looks a little better if you remember to switch to mode 0
Is there a VT100 terminal software for the BBC?

[Bobbi]

Termulator ROM maybe has VT100 emulation?

[!FOZ!]

My new serial ULA replacment PCB's arrived from China over Christmas, no more sharing 1 serial ULA between my machines.
20210101_150517.jpg

Hi Alan, are you willing to share the gerber and bom list for folks to make their own?

I am gathering parts to populate the replica BBC pcb.

Thanks for consideration.

[maniacminer]

If you're not going to fit the serial ULA, you can save a lot of soldering. Taking a look at the PCB you can omit;

IC7, IC33, IC35, IC42, IC74, IC75, SK5, SK4, R74, R75, R78, R79, R80, R82, R83, R86, R87, R88, R89, R90, R93, R95, R96, R97, R160, R161, R174, C28, C29, C30, C31, C32, C33, C34, C35, C38, C39, C43, C45, C59, Q1, Q2, Q3, D13, RL1

If you weren't going to use the composite video and UHF outputs you could save a whole "that's no moon" amount of soldering

IC50 is shared with the missing serial ULA componentry and you can omit;

IC46, IC47, IC48 (you'll need to connect pin #10 to pin #8 and no inverted SYNC) IC49, X2, UHF modulator, SK2, VC1, D19, D20, D21, D22, C45, C49, C50, C51, C52, C53, C55, C56, C58, R109, R110, R115, R116, R117, R118, R123, R125, R127, R128, R129, R130, R132, R133, R134, R135, R136, R137, R138, R139, R140, R141, R143, R144, R145, R146, R147, R150, R151, R152, R154, R156, R157, R158, R159, L1, Q7, Q8, Q9, Q10

[Alan00]

BBC-serial-ULA_2021-03-20.zip

(8.18 KiB) Downloaded 13 times

I had the PCB's made a few years ago and have attached the files.

Originally, I used the 1Mhz clock from the ADC IC, latter I used the 2Mhz clock for the serial ULA.
At 2Mhz Telstar worked well but the BBS's kept missing characters, so in the ESP-01 program I added a few delays.

Also only the 1K resistor is required as the ESP-01 requires 3.3V

I have 3 PCB's left, postage from Australia to UK is about 3 pounds if anyone wants one.

[!FOZ!]

BBC-serial-ULA_2021-03-20.zip
I had the PCB's made a few years ago and have attached the files.

Originally, I used the 1Mhz clock from the ADC IC, latter I used the 2Mhz clock for the serial ULA.
At 2Mhz Telstar worked well but the BBS's kept missing characters, so in the ESP-01 program I added a few delays.

Also only the 1K resistor is required as the ESP-01 requires 3.3V

I have 3 PCB's left, postage from Australia to UK is about 3 pounds if anyone wants one.

pcb.png
circuit.png
20230319_122322.jpg

Wonderful! I'll drop you a DM. Thanks!

[Alan00]

I attached the wrong ULA, this is the correct one

BBC-serial-ULA (2)_2023-03-19.zip

(13.44 KiB) Downloaded 22 times

[Alan00]

I have been asked for the program for ESP-01.

virtual_modem_3.zip

(4.14 KiB) Downloaded 18 times

The file has been zipped.
You will need to put your network name and password, doing this will make things a lot faster.

Connect to a different WIFI: ATWIFI<ssid>,<key>
Connect by TCP: ATDT<host>:<port>
See my IP address: ATIP
HTTP GET: ATGET<URL>
example ATDTglasstty.com:6502 will connect you to TELSTAR

The following modification are required for the Arduino program to work.

There is a green wire and a copper wire, the green wire is for control which I'm not using and is bridged out.
The copper wire feeds 2MHz to the serial clock on the 6850.

I programmed the esp-01 using the Arduino software and one of the USB programmers from Ebay.

[sweh]

FWIW, when I'm releasing WiFi code like this I "hide" the details. From the README I typically have lines such as

Code: Select all

You will need to make a file `network_conn.h` with contents similar to

    const char* ssid       = "your-ssid";
    const char* password   = "your-wpa-passwd";

So now my main code can just do

Code: Select all

#include "network_conn.h"
#include <ESP8266WiFi.h>
...
  WiFi.mode(WIFI_STA);  // Ensure we're in station mode and never start AP
  WiFi.begin(ssid, password);
...

And I can put network_conn.h in my .gitignore file. It means I never have to worry about my WiFi creds leaking and I can deploy direct from my source tree

e.g. https://github.com/sweharris/esp8266-oled-clock

[mpryon]

I'm hoping to build one of these serial ULA boards. I'm not completely certain about the voltage regulator needed.

Would this work?

https://www.digikey.com/en/products/det ... OPB/367019

thanks!

[mpryon]

I'm hoping to build one of these serial ULA boards. I'm not completely certain about the voltage regulator needed.

Would this work?

https://www.digikey.com/en/products/det ... OPB/367019

thanks!

as it turns out, yes those regulators do indeed work.

I'm having trouble getting Termulator to work properly but Commstar works.
Termulator doesn't seem to be sending the AT commands, nothing seems to happen. Weird.