Acorn Electron online? Any such hardware.

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uniforix
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Acorn Electron online? Any such hardware.

Post by uniforix » Wed Apr 08, 2020 8:50 am

Good morning all,

I hope isolation is treating everybody well.

I was just wondering, does anyone have an Acorn Electron able to communicate with the outside world and if you do, how do you do it? Is there a modern solution or something like a cable that does it through a PC? Rasp Pi?

Just interested to know :D

Anthony.
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Re: Acorn Electron online? Any such hardware.

Post by davidb » Wed Apr 08, 2020 10:14 am

Were you thinking of something like Econet, or something more straightforward like a modem? Stuart (aerworuld) was doing things with a modem.

I started thinking about Econet recently, having never really looked at it closely. Trying to get a mental model of how the hardware handles incoming data and how that is seen by the networking software. I found these sites interesting: I think I would probably try to do something a lot simpler and rely on much more powerful hardware to handle the networking side of things. :)

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Re: Acorn Electron online? Any such hardware.

Post by daveejhitchins » Wed Apr 08, 2020 10:40 am

The only 'outside' communications specifically designed for the Electron, that I know of, is the Slogger serial interface. There may be others that connect to the various interfaces on the AP5 - but they'll most likely have been designed for the bigger brothers in the Acorn range. I suppose MartinB's IIC interface could also be included as it could communicate with a larger connected-to-the-world device - big ? here.

I'll now wait for all the designs I've forgotten about :lol:

By the way, I've had an RS232 cartridge on my to-do list since the mid '80s :oops: I've been trying to find the 'rough' sketch I did at the time of conception - no luck yet - it's in one of the Forum posts . . .

Dave H :D

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Re: Acorn Electron online? Any such hardware.

Post by jgharston » Wed Apr 08, 2020 3:56 pm

daveejhitchins wrote:
Wed Apr 08, 2020 10:40 am
By the way, I've had an RS232 cartridge on my to-do list since the mid '80s :oops: I've been trying to find the 'rough' sketch I did at the time of conception - no luck yet - it's in one of the Forum posts . . .
Yeah, you sent it to me, it's "somewhere" on my PC. ;)

Code: Select all

$ bbcbasic
PDP11 BBC BASIC IV Version 0.32
(C) Copyright J.G.Harston 1989,2005-2020
>_

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Re: Acorn Electron online? Any such hardware.

Post by roland » Wed Apr 08, 2020 4:42 pm

uniforix wrote:
Wed Apr 08, 2020 8:50 am
I was just wondering, does anyone have an Acorn Electron able to communicate with the outside world and if you do, how do you do it? Is there a modern solution or something like a cable that does it through a PC? Rasp Pi?
You're asking this question a little bit too soon, so now I have to reveal my secret project.....

I am working on an interface for the Atom to use an ESP8255 wifi module to communicate with the Internet. It's nothing new and some people here have also worked or played with it. My base set up will be an extra interface board with a (dual) serial interface (ST16C2552CJ). One of the ports will be used to communicate with the Raspberry Pi and the other is for Wifi. For the software I am writing a Wifi network driver that handles all the basic stuff like connecting and disconnecting to a Wifi network, get a list of SSID's, connect to a server, retrieve data etc. This driver is pretty device independent and can easily be ported to the Electron or Beeb. At the moment I have a few base commands for working with wifi. At boot time my Atom retrieves the current date and time from the internet and sets the real time clock. Now I am working on a WGET command to retrieve a file from a web server. It's almost finished, I receive the file but I have to strip the HTTP headers and join the (1420 bytes long) data blocks together.

I have been thinking about making a cartridge for the Electron with the same hardware so I can use the driver for both computers. More information will follow in a few weeks so until that time, please treat this information as confidential and preliminary :mrgreen:
FPGAtom: 512 KB RAM, Real Time Clock and 64 colours
MAN WOMAN :shock:

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Re: Acorn Electron online? Any such hardware.

Post by daveejhitchins » Wed Apr 08, 2020 5:51 pm

roland wrote:
Wed Apr 08, 2020 4:42 pm
You're asking this question a little bit too soon, so now I have to reveal my secret project.....

I am working on an interface for the Atom to use an ESP8255 wifi module to communicate with the Internet. It's nothing new and some people here have also worked or played with it. My base set up will be an extra interface board with a (dual) serial interface (ST16C2552CJ). One of the ports will be used to communicate with the Raspberry Pi and the other is for Wifi. For the software I am writing a Wifi network driver that handles all the basic stuff like connecting and disconnecting to a Wifi network, get a list of SSID's, connect to a server, retrieve data etc. This driver is pretty device independent and can easily be ported to the Electron or Beeb. At the moment I have a few base commands for working with wifi. At boot time my Atom retrieves the current date and time from the internet and sets the real time clock. Now I am working on a WGET command to retrieve a file from a web server. It's almost finished, I receive the file but I have to strip the HTTP headers and join the (1420 bytes long) data blocks together.

I have been thinking about making a cartridge for the Electron with the same hardware so I can use the driver for both computers. More information will follow in a few weeks so until that time, please treat this information as confidential and preliminary :mrgreen:
=D> :-#

Dave H :D

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Re: Acorn Electron online? Any such hardware.

Post by mark71 » Wed Apr 08, 2020 9:56 pm

daveejhitchins wrote:
Wed Apr 08, 2020 5:51 pm
roland wrote:
Wed Apr 08, 2020 4:42 pm
You're asking this question a little bit too soon, so now I have to reveal my secret project.....

I am working on an interface for the Atom to use an ESP8255 wifi module to communicate with the Internet. It's nothing new and some people here have also worked or played with it. My base set up will be an extra interface board with a (dual) serial interface (ST16C2552CJ). One of the ports will be used to communicate with the Raspberry Pi and the other is for Wifi. For the software I am writing a Wifi network driver that handles all the basic stuff like connecting and disconnecting to a Wifi network, get a list of SSID's, connect to a server, retrieve data etc. This driver is pretty device independent and can easily be ported to the Electron or Beeb. At the moment I have a few base commands for working with wifi. At boot time my Atom retrieves the current date and time from the internet and sets the real time clock. Now I am working on a WGET command to retrieve a file from a web server. It's almost finished, I receive the file but I have to strip the HTTP headers and join the (1420 bytes long) data blocks together.

I have been thinking about making a cartridge for the Electron with the same hardware so I can use the driver for both computers. More information will follow in a few weeks so until that time, please treat this information as confidential and preliminary :mrgreen:
=D> :-#

Dave H :D
Cool :), i was pondering this the other day how to get the Elk and such on the internet in a useful way using a raspberry pi zero as played with a few. was wondering about the spi interface or serial connection as the zero would lend itself to a cartridge to fit innto the Plus1/rombox and get the zero to do the hardwork.

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Re: Acorn Electron online? Any such hardware.

Post by mr-macrisc » Thu Apr 09, 2020 2:49 pm

roland wrote:
Wed Apr 08, 2020 4:42 pm
uniforix wrote:
Wed Apr 08, 2020 8:50 am
I was just wondering, does anyone have an Acorn Electron able to communicate with the outside world and if you do, how do you do it? Is there a modern solution or something like a cable that does it through a PC? Rasp Pi?
You're asking this question a little bit too soon, so now I have to reveal my secret project.....

I am working on an interface for the Atom to use an ESP8255 wifi module to communicate with the Internet. It's nothing new and some people here have also worked or played with it. My base set up will be an extra interface board with a (dual) serial interface (ST16C2552CJ). One of the ports will be used to communicate with the Raspberry Pi and the other is for Wifi. For the software I am writing a Wifi network driver that handles all the basic stuff like connecting and disconnecting to a Wifi network, get a list of SSID's, connect to a server, retrieve data etc. This driver is pretty device independent and can easily be ported to the Electron or Beeb. At the moment I have a few base commands for working with wifi. At boot time my Atom retrieves the current date and time from the internet and sets the real time clock. Now I am working on a WGET command to retrieve a file from a web server. It's almost finished, I receive the file but I have to strip the HTTP headers and join the (1420 bytes long) data blocks together.

I have been thinking about making a cartridge for the Electron with the same hardware so I can use the driver for both computers. More information will follow in a few weeks so until that time, please treat this information as confidential and preliminary :mrgreen:
Superb :)

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Re: Acorn Electron online? Any such hardware.

Post by uniforix » Sat Apr 11, 2020 9:33 pm

roland wrote:
Wed Apr 08, 2020 4:42 pm
You're asking this question a little bit too soon, so now I have to reveal my secret project.....

I am working on an interface for the Atom to use an ESP8255 wifi module to communicate with the Internet. It's nothing new and some people here have also worked or played with it. My base set up will be an extra interface board with a (dual) serial interface (ST16C2552CJ). One of the ports will be used to communicate with the Raspberry Pi and the other is for Wifi. For the software I am writing a Wifi network driver that handles all the basic stuff like connecting and disconnecting to a Wifi network, get a list of SSID's, connect to a server, retrieve data etc. This driver is pretty device independent and can easily be ported to the Electron or Beeb. At the moment I have a few base commands for working with wifi. At boot time my Atom retrieves the current date and time from the internet and sets the real time clock. Now I am working on a WGET command to retrieve a file from a web server. It's almost finished, I receive the file but I have to strip the HTTP headers and join the (1420 bytes long) data blocks together.

I have been thinking about making a cartridge for the Electron with the same hardware so I can use the driver for both computers. More information will follow in a few weeks so until that time, please treat this information as confidential and preliminary :mrgreen:
Wow! That sounds amazing :-) Will keep an eye out for updates!
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Re: Acorn Electron online? Any such hardware.

Post by roland » Sun Apr 12, 2020 10:58 pm

uniforix wrote:
Sat Apr 11, 2020 9:33 pm
Wow! That sounds amazing :-) Will keep an eye out for updates!
Here's a small update: I got a little step further with my WGET command. I can download a file from my webserver (e.g. http://acornatom.nl/snapper.atm) and it is loaded together with http headers and block size information info the memory area #5000 - #7FFF (that's what I have defined as my receive buffer). Then, a copy routine is started to filter out the http header and read the atm header for figuring out the load address (#2900). After that it starts copying the real data to #2900 onwards. This goes fine for the first block of 1420 bytes, but from the second and third block it loses one byte so my downloaded file misses two bytes (and snapper won't run). I have to find and solve this error and then I have my prove of concept and can I share all the details with you. So please have a little more patience....

For the Elk version I am thinking about a cartridge with 8 KB ROM for the basic driver and some essential WIFI commands (like *JOIN, *LEAVE, *LAP and *WGET) and 8 KB RAM as a receive data buffer. That would be the easiest hardware setup but it limits to load file > 7KB or the interface could have for example 32KB or even 64KB as paged RAM and use that for a receive data buffer and if the wifi module is not used the paged RAM is available for other purposes. Perhaps one of the Dave's can think about this when I get to that point. I will also need some support in writing the ROM. But first, I want to get this working on my Atom.....
FPGAtom: 512 KB RAM, Real Time Clock and 64 colours
MAN WOMAN :shock:

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Re: Acorn Electron online? Any such hardware.

Post by mr-macrisc » Sun Apr 12, 2020 11:31 pm

Could it potentially have some of same commands avail as the master Ethernet interface (networked doom would be rather cool)

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Re: Acorn Electron online? Any such hardware.

Post by roland » Sun Apr 12, 2020 11:56 pm

I don't know the Econet (protocol) but I think it must be possible to write Econet compatible commands. It's possible to set up a tcp connection and then put the esp8266 in pass-thru mode so you can send anything you want.
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MAN WOMAN :shock:

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Re: Acorn Electron online? Any such hardware.

Post by Multiwizard » Mon Apr 13, 2020 6:57 am

roland wrote:
Sun Apr 12, 2020 10:58 pm
But first, I want to get this working on my Atom.....
Nice Roland... =D> :D =D>


Greetings, Wim... :-)

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Re: Acorn Electron online? Any such hardware.

Post by oss003 » Mon Apr 13, 2020 7:56 am

Yes, nice project Roland.
Do you have a video of how it's working?

Greetings
Kees

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Re: Acorn Electron online? Any such hardware.

Post by roland » Mon Apr 13, 2020 9:27 am

Not yet, I have just found the errors that probably cause the copy faults. For the first block of data the second error undoes the first error but for the next blocks there is only one error that re-occurs. I'll try to fix them later today.
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MAN WOMAN :shock:

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Re: Acorn Electron online? Any such hardware.

Post by uniforix » Mon Apr 13, 2020 11:09 am

roland wrote:
Mon Apr 13, 2020 9:27 am
Not yet, I have just found the errors that probably cause the copy faults. For the first block of data the second error undoes the first error but for the next blocks there is only one error that re-occurs. I'll try to fix them later today.
Very exciting, if this makes it to an end user product will definitely down for a purchase =D> Can't wait to see more updates.
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Re: Acorn Electron online? Any such hardware.

Post by roland » Mon Apr 13, 2020 8:01 pm

I have started a new topic for the Atom ESP8266 WiFi at viewtopic.php?f=44&t=19056
FPGAtom: 512 KB RAM, Real Time Clock and 64 colours
MAN WOMAN :shock:

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Re: Acorn Electron online? Any such hardware.

Post by roland » Sun Apr 19, 2020 10:17 pm

Now that I have almost finished the hardware for the Acorn Atom online I can start thinking about the Electron online module. I am thinking about a pcb that goes into a Plus1 slot and has room for an UART, the ESP8266 module, a ROM socket for the software and some RAM as buffer memory. I think the buffer memory is necessary because the Elk is quite slow when it comes to lower RAM access and we really need all the speed we can get to keep up at 115200 baud.

My first issue: will 8K ROM and 8K RAM in one bank be sufficient? For the software that I have up to now that might be sufficient ROM. But 8K buffer is not much. So maybe a 128K paged RAM might also be a nice option. The Electron OS only supports 64K of pages RAM but there is a bit available in the 16C2552 UART that can do the bank switching of those two 64K blocks.

My second issue: I have never written a sideway ROM for the Electron. So I have to study that also before I can start programming. But I am quite sure that there are good tutorials, documents and examples to give it a start.

To be continued.....
FPGAtom: 512 KB RAM, Real Time Clock and 64 colours
MAN WOMAN :shock:

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Re: Acorn Electron online? Any such hardware.

Post by roland » Sun Apr 26, 2020 8:49 pm

Today I have started working on a design for the Electron version of my ESP8266 module for the Atom. I will give a short description of the circuit here.

The control logic is done by a XC9236XL CPLD (which might be replace by a 9572 if necessary). The logic in this CPLD does take care of the following:
  • Address decoder for the ST16C2552 dual UART at address space &FC60 - &FC6F
  • Address decoder for the paged RAM latch at &FCFF
  • Generate IOR (read) and IOW (write) signals for the memory and UART
  • Divide the 16MHz to get an almost 1.8432MHz clock signal for the UART
  • Level shifter for the 3.3V RX signal of the ESP8266 module
  • Light organ for the RX and TX signals
The UART has two channels. The B-channel is dedicated for the ESP8266 module. Two control signals (DTR and RTS) are used to enable/disable and reset the ESP8266 module. The A-channel will be routed to an optional header connector so you can use it for generic RS232 communications.

I have added a SST39SF010 EEPROM for the WiFi commands and driver. This will be a service ROM. There is a second bank available for another sideway ROM (the space is available so why not use it?). Since there is more space I also routed MFA (multi-function output A) of the UART to the EEPROM (A15) so if you don't use the WiFi commands you can have another two banks of sideway ROM as well. Please note that after a reset this MFA will go "high" so these extra ROMS are not available during initialization of the Electron.

The 128 KB of RAM is organized as two banks of 64 KB paged RAM at &FDxx. Switching between banks is done by MFB (the multi-function output of port B). This memory will be used as buffer during WiFi transfers but if you do not use the WiFi it should behave like normal paged RAM.

I have a few questions:
  1. The I/O space &FC60 - &FC6F are officially reserved for a 6850 UART. Are there any objections to use this space for my UART? If so, what would be a better address range for my 16C2552? It needs 16 addresses.
    For Master compatibility &FCD0-&FCDF or &FCF0 - &FCFF might be a better option. In fact, using the last range makes the page ram latch read/write since the last byte of the UART is a scratch register. I might go for that address :)
  2. Officially the address for the paged RAM latch is &FCFF but the addresses from &FCF0 - &FCFE are not documented and seem to be free. Could it do any harm or cause collisions with existing (known) hardware if I do not decode this single address but use the complete block instead? That saves me four CPLD inputs.
    The latch must be fully decoded for BBC Master compatibility.
  3. The signals IOR and IOW are equivalents of the signals NRDS and NWDS in the Atom. However, those are a combination of R/nW and Phi2. I have read that on the Electron cartridge slots there is Phi1 and not Phi2. Are there any examples how to create the proper IOR and IOW signals? I think that I could stretch the signals in the CPLD but I have not yet investigated the exact timings and I don't need to if this has been done before :mrgreen:
    I got information from Dave how to do this.
  4. Is there a KiCad footprint available for the PCB edge connector?
    Got it from Myelin.
  5. The ESP8266 module may source up to 170 mA and the Advanced User Guide mentions that a cartridge may consume a maximum of 50 mA. So I have to add a separate connector for power or ...... can I silently ignore the maximum of 50 mA? Why is this limitation, is it because of the Elk's power supply (I guess so) ? Anyway, using the internal power supply would make it easier to use the cartidge but it should never ruin any Electron of course [-X
    There will be a power connector on the board. Just to be sure.....
  6. Is it possible to derive an almost 1.8432 MHz clock out of a 16MHz signal? 16/1.8432 = 8.68. How to do that in a CPLD?
    This is already worked out and tested.
So, that is my work on this project up to now. Please have a look and return your comments here. Especially the RAM / ROM part of the circuit need a good review by Electron Hardware experts (with the capital H of Mr. Hitchins [-o< ).

I think this board will be double sides but with a lot of SMD components. I think that a suitable RAM and CPLD are not available any more as PDIP and PLCC44. The UART is PLCC44 and for the EEPROM I will use a PLCC32 version because that is easier to program (at least for me). Using 0805 size capacitors, leds and resistors is quite doable with hand soldering.

BTW I have stopped ordering "active" components (like voltage regulators, memory and so) from Chinese webshops. That latest shipments were all wrong. I got voltage regulators with the input and output pins swapped, I ordered XC9572XL devices and I got XL9572's and when I made a complaint the seller simply said that those are the same. So in future projects no more cheap Chinese stuff.


Edit 1: some of the questions are already answered.
Edit 2: remaining questions also answered.
Attachments
ElkWifi-preliminary.pdf
(220.06 KiB) Downloaded 56 times
FPGAtom: 512 KB RAM, Real Time Clock and 64 colours
MAN WOMAN :shock:

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Re: Acorn Electron online? Any such hardware.

Post by roland » Mon Apr 27, 2020 11:45 am

roland wrote:
Sun Apr 26, 2020 8:49 pm
Is it possible to derive an almost 1.8432 MHz clock out of a 16MHz signal? 16/1.8432 = 8.68. How to do that in a CPLD?
I have found this theory on https://excamera.com/sphinx/vhdl-clock.html that seems worth a try.

It's always possible to place a 1.8432 MHz crystal on the PCB but that takes extra space and we do have a 16MHz clock available. So if I can avoid an extra component by using the already available resources then I want to work that out....
FPGAtom: 512 KB RAM, Real Time Clock and 64 colours
MAN WOMAN :shock:

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Re: Acorn Electron online? Any such hardware.

Post by roland » Wed Apr 29, 2020 12:45 pm

As you can read in this topic ( viewtopic.php?f=11&t=19157 ) the 1.8432 MHz clock generation for the UART is already settled.
1_828MHz.jpg
Any comment on the memory selection and my other questions?
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MAN WOMAN :shock:

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Re: Acorn Electron online? Any such hardware.

Post by roland » Wed Apr 29, 2020 9:03 pm

I have updated the diagram with the following changes:
  • Added a pull-up resistor to pin 30 (CS2) of the RAM chip.
  • Corrected a bug which connects 3.3V to rx-esp.
  • Added A0 .... A3 to the CPLD
  • Removed the RESET and nRST signals from the CPLD to free two I/O pins
  • Inverted RESET to the UART with a NPN transistor
  • Added MADET and MRnW to the CPLD
  • Renamed RnW to ERnW
These changes should make the cartridge compatible with the Electron and the BBC Master.


Edit: note to myself, add 180 Ohm resistor to 16 MHz track near the CPLD.
Attachments
Elk-WiFi-1.0.1.pdf
Version 1.0.1 is still preliminary !
(226.99 KiB) Downloaded 34 times
FPGAtom: 512 KB RAM, Real Time Clock and 64 colours
MAN WOMAN :shock:

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Re: Acorn Electron online? Any such hardware.

Post by tone76 » Fri May 01, 2020 3:26 am

roland wrote:
Wed Apr 08, 2020 4:42 pm
I am working on an interface for the Atom to use an ESP8255 wifi module to communicate with the Internet. It's nothing new and some people here have also worked or played with it. My base set up will be an extra interface board with a (dual) serial interface (ST16C2552CJ). One of the ports will be used to communicate with the Raspberry Pi and the other is for Wifi. For the software I am writing a Wifi network driver that handles all the basic stuff like connecting and disconnecting to a Wifi network, get a list of SSID's, connect to a server, retrieve data etc. This driver is pretty device independent and can easily be ported to the Electron or Beeb. At the moment I have a few base commands for working with wifi.
Would it be too soon to put in a preorder for a Beeb version? :D This sounds really promising.
Acorn Electron
BBC Model B (either too many or not enough)
BBC Model B+ 128K
BBC Master 128 x 2

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Re: Acorn Electron online? Any such hardware.

Post by jms2 » Fri May 01, 2020 9:40 am

This project looks really interesting! Also... I can help you with the edge connector. I didn't design it myself, but I found it on the net and I can confirm it works perfectly. Most probably it came from a project on here - I'm not sure though.

My biggest problem is that I don't understand how to manage libraries of components in KiCad at all, so I have just taken the folder that I downloaded and zipped it up. I have no idea how to import this, but hopefully you will be able to make sense of it.
AcornElectronCartridge-f6d90cacc131.zip
(92.13 KiB) Downloaded 28 times

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Re: Acorn Electron online? Any such hardware.

Post by roland » Fri May 01, 2020 11:37 am

tone76 wrote:
Fri May 01, 2020 3:26 am
Would it be too soon to put in a preorder for a Beeb version? :D This sounds really promising.
If it is simple to convert the RS423 to 0V - 3V then the interface for the Beeb can be very simple. The Beeb has room for sideway ROMs so the only thing that is lacking is the extra buffer memory at &FDxx. But perhaps that is not directly needed since I can store the received data also in the main system memory.
FPGAtom: 512 KB RAM, Real Time Clock and 64 colours
MAN WOMAN :shock:

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Re: Acorn Electron online? Any such hardware.

Post by roland » Fri May 01, 2020 11:40 am

jms2 wrote:
Fri May 01, 2020 9:40 am
My biggest problem is that I don't understand how to manage libraries of components in KiCad at all, so I have just taken the folder that I downloaded and zipped it up. I have no idea how to import this, but hopefully you will be able to make sense of it.
Thanks, I'll have a look at it. The folder AcornElectron.pretty might be enough. In KiCad you can then add the library to the library path. I will report back later.
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MAN WOMAN :shock:

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Re: Acorn Electron online? Any such hardware.

Post by myelin » Fri May 01, 2020 6:25 pm

I have a fairly battle tested cartridge edge footprint in https://github.com/myelin/myelin-kicad.pretty also -- https://github.com/myelin/myelin-kicad. ... .kicad_mod is the file. MIT license.
SW/EE from New Zealand, now in Mountain View, CA, making BBC/Electron hardware projects for fun.
Most interesting: Arcflash, FX2+PiTubeDirect Tube/Cartridge adapter, USB cart interface.

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roland
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Re: Acorn Electron online? Any such hardware.

Post by roland » Fri May 01, 2020 7:34 pm

I had a look at both libraries, Myelin's is more usable as the connector is in "one piece", the other design has two separate footprints, each for one side. Besides that, the ESP8266-01 module footprint is also welcome :lol:

Thanks Jms2 and Myelin for your help.


Today I practised a bit more on SMD soldering by removing some components from an old PCB and than put them back on it. I think I can now manage a CPLD and RAM ic :mrgreen:
FPGAtom: 512 KB RAM, Real Time Clock and 64 colours
MAN WOMAN :shock:

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daveejhitchins
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Re: Acorn Electron online? Any such hardware.

Post by daveejhitchins » Sat May 02, 2020 7:52 am

myelin wrote:
Fri May 01, 2020 6:25 pm
I have a fairly battle tested cartridge edge footprint in https://github.com/myelin/myelin-kicad.pretty also -- https://github.com/myelin/myelin-kicad. ... .kicad_mod is the file. MIT license.
I can provide a dxf of the footprint I use - if it would help?

Dave H :D

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roland
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Re: Acorn Electron online? Any such hardware.

Post by roland » Sun May 03, 2020 3:05 pm

I can use Myelin's footprint. Thanks anyway Dave.

I have updated the diagram again. It has some significant changes compared to version1.0.1:
  1. Since the signal nPGFC has all the information for decoding page &FCxx (what's in a name?) I don't need the address lines A12 ... A15 in the CPLD. That frees four inputs. So I brought the reset line back and send an inverted output to the UART. This saves a transistor and two resistors.
  2. For what it is worth, I feed ROMQA also in the CPLD although I am not convinced that I will need it. It is mainly used for selecting one of the two sideway ROM (banks). In an example file from Dave I saw that he used it so I added it to the CPLD, better safe than sorry.
  3. I have worked out the VHDL for the CPLD and it does not fit into a XC9536XL so the CPLD is replaced by a XC9572XL.
  4. There is a RAM disable jumper added to CS2. This might be nice if you switch the board into a system that already has paged RAM. Normally CS2 is held high by a resistor and by tying this input to GND the chip won't be enabled. If there is no paged RAM in your computer(s) you can leave this jumper. If your computer(s) already has paged RAM you can also omit the RAM memory on this board. Just like it is not necessary to use the ROM on this board if you have alternative sideway ROM or RAM available.
  5. I have replaced the single row connector for serial output port A to a 2x5 connector. This takes less space on the board and the pin-out is compatible with serial DB9 pinout. The tenth pin is a +5V connection so you can also hook up a small board with a MAX232 to produce real RS232 signals.
Attachments
Elk-WiFi-1.0.2.pdf
Version 1.0.2: almost final.... :)
(239.24 KiB) Downloaded 42 times
FPGAtom: 512 KB RAM, Real Time Clock and 64 colours
MAN WOMAN :shock:

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