M4 Board – Retrofun, 8-Bit Amstrad CPC WiFi

Description and purpose of the “M4 board”.
m4board_v2
The M4 board, features as previously described a ST32F407 Cortex M4 MCU, connected via SPI to a ESP8266 WIFI module, and 18 GPIO’s routed via a GTL2000 voltage translator chip.

It was meant to be connected to the old the Amstrad CPC (z80 based) computer via it’s expansion port.
As with most old age computers, it runs with 5V I/O, here is where the GTL2000 chip came in handy.
The signals driven through the GTL2000 are output signals and the bi-directional data bus (D0-D7).

Input signals are connected directly to the ST32F407 Cortex M4 as it is 5V tolerant.

The idea was to provide WiFi to the Amstrad CPC, for easy and fast data exchange between it and a PC, but also direct internet access.

ROM BOARD emulation
First prerequisite was the ability to run code on the Amstrad via the M4 MCU so no additional loading (i.e. disc) would be needed.
It would be done by mapping a ROM in the Amstrad addressable space, this ROM would be in the M4 ram.

IORQ and WR will occur when a ROM is selected, data lines will contain the ROM number.
ROMEN and RD will occur when a read is happening from the currently selected ROM, address lines have the address, ROM data will be send back over the data lines.
A fairly trivial task, but the timing is tight having to bit bang the gpio, do direction changes on gpio’s mapped as data lines, even when the bus runs at only 4MHz.
Much time spent optimizing the handler in ARM assembler, it finally worked.

SD card storage
Being able to run code via the ROM board emulation, it would be nice to have native r/w storage.
A micro SD card slot connected to the M4 SDIO lines, was meant for this purpose.
An transfer interface from the Amstrad CPC to the M4 was designed.
Two I/O ports were assigned when an IORQ happened, one for receiving data on the M4 and one for telling it data was send, so it could process.
This was done as it’s easy to store data (low clock count), but takes additional time to process them.
When the 2nd port is written, the MCU sends BUSRQ signal to the Z80 CPU, which will ‘freeze’ the z80 CPU at the end of the current cycle, now the M4 has the time it needs to process the incoming data, before resuming the Z80 CPU and responding.
Responses are done in the ROM space, which of course is read only on the CPC, but R/W on the M4, as it is kept in the M4 ram!
Next up, was to hook the system bios/firmware functions, that do file related I/O to tape and disc on the original system and re-directing them to the sdcard.
Thus native file access from the SD card is possible, providing the CPC with up to 32GB (or more) of storage via SD card.

WiFi & Internet
In short the connection between ESP8266 and the M4 was done via SPI as IPC.
To allow internet/WiFi access from the Amstrad CPC itself, it sends a command to the M4, which again sends an IPC call to the ESP.

WEB interface
The ESP8266 hosts a WEB server, where various settings can be altered.
web_interface1 web_interface2

RTC
A battery mount was put on the board, making it possible to provide Real time clock as well via the RTC in the ST32F407.

What it does
Emulate Romboard, currently up to 16 roms, can be uploaded/removed via Web Interface.
Download files from internet via WiFi.
Mass storage to SD card, via native file I/O. R/W support. Emulated as drive A.
Can use DSK files on the SD card too, but only for file read access and sector reading via firmware call.
Upload files via web interface.

See a short demonstration here:

To do
Finish commands.
Lots of error checking.
Bug fixing.
More commands.
Other features.
hooked_up_to_la
Should anyone be mad enough to want a similar interface for their Amstrad CPC (or other suggestions), don’t hesitate to put a comment.
If enough are interested, I will run a batch + it’ll motivate me to finish and polish things up.

-Duke

166 thoughts on “M4 Board – Retrofun, 8-Bit Amstrad CPC WiFi”

  1. That’s one cool board! 🙂

    I’d have one in a crack if there was any available! 😉

    Dabz

    Reply

    1. Hi Duke
      I see this is an old post, but are boards still available (assembled)? I would be interested in one.
      Thanks
      Scott

      Reply

      1. Hi Scott,

        They are still available (build on demand). Lead time is about 5-6 weeks.
        Will email you shortly.

        Regards,
        Duke

        Reply

        2. I am also interested in one, would be for the 464+, I live in Spain, please email me if you see the message.

          Reply

        3. Another one interested. CPC6128 here. Let me know if you still have available and the price. I’m in Spain.

          Reply

    1. Hi Duke, I’m interested in this fantastic board. I’m from Spain. When you can please email me. Thanks.

      Reply

  3. Hi

    Very nice interface! Is the software/hardware open source? I’m interesting on emulating it on my spectrum and cpc emulator, ZEsarUX. I have already emulated other sd interfaces, like the divmmc, zxpand or the divide

    Thanks!

    Reply

  4. Hi Duke,

    This is one cool board.
    I really like the web interface feature.

    Could be mad enough to want one, if the price is right. 🙂
    Any thought on how much is it going to be?
    (Probably very early to ask, but… 🙂 )

    Will this board have extra RAM, like on the Symbiface II interface?
    (I am not sure, this might not be necessary, maybe becasue of Symbos compatibility….)

    What filesystem can be used for the SD card? Fat32?

    I own a Schneider CPC, will it be possible to connect this board to
    its centronix expansion ports?

    Tamas

    Reply

    1. Hi Tamas
      Thanks.
      The price is going to be 40 euro for the board. There is no RAM expansion build into it, I originally wanted to add another 64K (from the 192K of the cortex) but there is simply not enough processing time for the code logic, when also doing romboard emulation and I/O port transfer.
      Filesystem is plain fat 32.
      For the Schneider, yes, but you need a cable (not included with the board). You can look for MX4 (MotherX4) it should work with that.
      Check out the cpcwiki forums too, there is a lot of talk about it: http://www.cpcwiki.eu/forum/amstrad-cpc-hardware/amstrad-cpc-wifi/

      Reply

      1. Hi Duke,

        Thank you for your response. I believe the price is reasonable.
        I am definitely interested, please count me in for one board.
        Do you have any idea when a batch could be released?

        I am not being impatient, I just would like to know
        when I need to get the payment ready. 🙂
        (Weeks, months…)

        One more question, does this board need any external power
        source? If yes, can you recommend one that would work with it?

        Thank you

        Tamas

        Reply

        1. Tamas,

          I hope about 4-5 weeks for the first to start shipping, I need to make a lot so I don’t know how long it will take.
          It should be OK with the CPC power supply, but you can also use an external USB power supply (5V, 1A).

          Reply

          1. Hi,

            So not earlier than June/July…
            OK, thanks for all your answers and for doing this!
            Please let me know when it is time to purchase. 🙂
            (But I will try to monitor the cpcwiki.eu forum,
            I am a member there.)

            Tamas

  5. Hi Duke

    Well done. I’m *really* interested in such a M4 and also might offer some very limited time in tests, bugfixing and extension. The main question resides on the M4: is it running an OS, or is it a native running application, handling the IO? I assume the later one. So some more info might be neccessary for contribution on that (I’m not an ARM specialist).

    Reply

  6. Hi Duke. Firstly, thanks for making things like this board. And secondly, I am really interested in a M4 too, if it is possible. Regards.

    Reply

    1. Hi Manuel

      Thanks. The first batch of boards is sold out already, but if atleast 10 more want one I will do a new batch (2 out of 10 now, so I think it’s possible). I’ll put you on the list.

      Reply

        1. Hi Duke. I received (months ago) and…it is outstanding! I wonder if it would be possible to ask for another M4, this time with a MX4 connector (it’s for a 6128+). Thanks.

          Reply

          1. Hi Manuel

            Good to hear. Yes it’s still possible to order more, there’s a bit of processing time needed (a couple of weeks).

            -Duke

  9. I got mine yesterday, these boards are awesome! In a stroke it replaces the X-Mass, X-Mem* and HxC devices.

    Now we have to simply hope a FTP Client and IRC Client are written to use this card on the CPC 😉

    Craig

    * OK you still need the X-Mem for the ram expansion.

    Reply

  10. Hi, I’m interested in acquiring this amazing piece for my Amstrad CPC 6128. How can I order? Cheers.

    Reply

  11. Hi,
    I want a M4 with Edge connector (I do not own MX4 board, so, i have to connect directly to my CPC).
    Thanks!

    Reply

  12. Hi Duke, I’m interested in acquiring this fantastic piece for my Amstrad CPC 6128 too; how can I order?

    I don’t know if it is neccesary to have any connector or similar or not, or I can connect it directly, please tell me ok?

    Congratulations, awsome job.

    Reply

  15. Hello Duke,
    I would like to order a M4 board with MX4 connector and a PCB adapter assembled. Can you email me back?

    Reply

  17. I think my CPC 6128 needs this! Please let me know how to get hold of a board I can directly use with my machine.

    Reply

  21. hola DUKE.

    Quiero 1 M4 board con un conector para un amstrad cpc versión española y otro conector para amstrad cpc plus versión española.

    te puedes poner en contacto para poder tenerlo. muchas gracias

    ahora te lo pongo en ingles con google, por que yo solo hablo español.

    Hello duke

    I want 1 M4 board with a connector for an amstrad cpc spanish version and another connector for amstrad cpc plus spanish version.

    You can contact in order to have it. thank you very much

    Now I put it in English with google, because I only speak Spanish.

    Reply

  22. Hello,

    I am from UK. This is such an amazing project and good to see CPC is still being expanded even in 2016.

    I would like to purchase a board if possible?

    Please let me know if it is possible, thank you. I have CPC464 & CPC6128

    Kind regards,

    Reply

  23. Hello! Congrats for the amazing project. I would like to buy one M4 board. Please contact me back to arrange.
    Thanks in advance!

    Reply

  24. Hi, I purchased one M4 board from Duke last June (I think it was the first batch…). I ordered it with edge connector. Now I have an MX board and I would like to plug the M4 to it… Somebody is interested (including you Duke) in an exchange… My board is in excellent state … I only plugged it a couple of times and it works perfect… Thank you in advance
    Best regards

    Reply

    1. Hola.

      Soy Manel, de España. Ponte en contacto conmigo si aún tienes el interface. El conector Edge es para los primeros CPC, ¿Verdad? Gracias.

      Reply

      1. Si, pero me gustaría conectarlo a la MX4… He pedido un cable que aún no me ha llegado. Cuando me llegue lo probaré si no quedo satisfecho podría cambiarte la M4 Edge connector por una M4 Centronics o vendértela y comprar otra a Duke con conector centronics… Mi email es jomicamp@hotmail.com

        Reply

  26. Hello Duke,
    Congratulations on the project.
    I would be interested in an M4.
    Please add me to the list.
    Thank you.

    Reply

  27. Hello.

    Thanks for this amanzing project. Do you expect to make an unit with RAM Expasion? It would be the major achievement I can imagine together with unlock 8.3 chr name limitations. Would you modify this in the future or your card will be as is?

    I own a CPC6128+ and a CPC464. Centronics and Edge Connectors. Maybe is possible to get a conversor to use in both systems, doesn´t it?

    Thanks again and merry Xmass.

    Reply

    1. Hi
      Sorry for late reply, just got home from xmas holidays.

      As it is, I don’t plan to make a version with RAM expansion. There is no 8.3 char limitation anymore, latest firmware has |ls command and support long filenames.
      For connectors, it is possible to buy version with MX4 (plain IDC) connector and I also have cables:
      MX4 to Edge connector adapter 7 euro (for regular CPC464/664/6128)
      MX4 to Centronics connector 7 euro (for CPC+ and Schneider CPC6128).

      Reply

  29. Hi, I’m interested in acquiring this amazing piece for my Amstrad CPC 6128. How can I order?

    Reply

  30. Hello Duke! I’d like to buy one board for the Amstrad cpc6128. Congratulations for the project.

    Reply

  31. Hello

    This looks really fett. I’d like to order one with the edge connector (regular cpc 6128) if it’s still possible.

    Reply

  32. Hello Duke,
    I’ve been just reading the cpwiki thread. Really fantastic job! Congratulations. Seems the final device for Amstrad CPC, from my point of view of course.

    That’s why I would like to know if I am not too late to order 1 board, with Edge connector, vertical position (I think it is the current version). My CPC is regular CPC6128.

    Thanks a lot!

    Reply

  33. Hi Duke

    Been getting back into the CPC scene after a few years and just found out about your fabulous work on cpcwiki.

    I’d like to order 1 board with edge connector for my regular 6128. If that’s still possible please send me the relevant info.

    Thanks

    Reply

  35. Hello, Folks.
    I just received this some kind of miracle yesterday. I had only time to do a few tests. My first impression: MUST OWN FOR CPC.

    Amazing transfer speed. Lots of improvements in this updated 2.0 firmware. I had to do a lot of research but I´m glad with my Little beauty.

    Note: Tested only on my CPC6128 PLUS. Need to to things on standard 6128 and 464.

    Reply

  36. I am interested in one plus two adapters one for old school CPCs and one for the plus range. Would that be possible?

    Reply

  41. Hi, I’m interested in acquiring this great piece for my Amstrad CPC 6128.

    Thanks in advance.

    P.D.: You are my new God!

    Reply

  43. Hi there,
    I own an Amstrad CPC 6128 and would like to buy an M4. Am I right in thinking that I can store DSK images on the SD card in the M4, and then run DSK images from the M4? Would I need any additional software? Is it fairly easy to use? Which would be the best M4 to get so that I can mainly run DSK images and get W-FI access?

    Nandan

    Reply

    1. Yes it can use DSK images, just as shown in th video. No extra software is needed, everything can be configured via a browser, aswell as uploading DSK’s and files.
      The M4’s have same functionality, only difference is the connector (PCB layout has also changed a bit, but its only cosmetic).
      Email sent.

      Reply

  46. Hi, I would love one of these to please.

    I have a CPC6128 with an IDC socket (pins) soldered onto the edge connector to if you can send one that has no connector fitted then I can take it from there.

    I have Paypal and CC but not BC. I would prefer Paypal if you can do that.

    Do you still have some in stock or will it take a while?

    I am in Australia.

    Reply

  47. Hi!

    I would like to buy am M4 board with edge connector (CPC464 & CPC6128 spanish version).
    Thanks
    A.Garrido

    Reply

  48. Hello

    I would like to buy M4 board with edge connector (CPC464) spanish version.
    😉
    thank you
    R.Frau

    Reply

  57. Hi, duke. I would like to order an m4 for an amstrad 6128 Spanish model. I wait for your email when possible. Greetings and thank you

    Reply

  58. Hello. I want to buy one M4 board for me. I heve got a Amstrad CPC 6128. Could you tell me if I can buy one for me? thanks

    Reply

  59. Hi, Duke, I am very interested in purchasing an m4 board with mx4 connector, with two cables, one mx4 to centronics (for my 464 plus) and the other mx4 to edge (for my cpc 464), waiting for your news, greetings

    Reply

  60. Nice work, dream is become reality, and now, I wanna absolutely this wifi card for my 6128…
    How can I have this treasure? Mail me a link to buying this jewel! PLEASE!

    Reply

  61. Hi i want to buy your M4 versión for plug directly to my cpc. Please tell me how can i get one of this cool add no. Regards

    Reply

  62. Hi! I would like to buy an M4. And one question. Can it write to the SD disk, or only read?

    Reply

    1. It can write directly to the FAT32 filesystem of the microSD card.
      It cannot write inside DSK images yet.

      Reply

  63. Hello Duke, I wanted to say your work is amazing! It made me want to fire up my old Amstrad again.
    I would like to order a M4 board with edge connectors for my CPC 6128.
    Thank you!

    Reply

  64. Hi Duke,

    Seen a youtube video on the M4 Board and I will be getting a Amstrad CPC6128 but the drive is faulty (I suspect a drive belt has gone) for which I have ordered a replacement drive belt. I am interested in purchasing the M4 board for the CPC6128 which I believe I will need the MX4 to Edge connector.

    One question if I can repair the internal FDD how will the M4 board work with the internal FDD?

    How much would it cost for the board and connection cable for shipment to the UK?

    Can you send me an e-mail containing updated pricing inc. shipping to UK for both the board and cable.

    Thanks in advance

    Edwin

    Reply

    1. Yes, it will work along with the internal FDD (|disc use disc drive, |sd use sd card).

      M4 board is available with both edge connector and IDC/MX4 connector (which will need a cable for Centronics or an adapter for Edge connector).

      Email sent.

      Reply

  65. Hi I am also insterested in buying an M4 wifi board for my CPC6128 please.

    I wonder if you can email details on how to buy if you’re still producing them and pricing. I’m in the UK.

    I’m hoping to buy it all ready made and ready to go so it can just plug in the back of the 6128 please with the connectors etc already in your kit?

    Thanks again.

    Reply

  66. Hi I emailed also about ordering an M4 board but I was also looking at a PACE RS232 with a Wifi232 modem so I could connect to a BBS with my CPC. Does or will just the M4 board support this by itself? That would be really useful if possible?

    Reply

    1. As for BBS. I don’t know, there is commands to connect to the internet (ie. httpget) and a sockets interface, so it should be possible to write software for this.
      I don’t have any plans to do so myself though.

      Reply

  69. Hi there! This is fantastic! I am also insterested in buying an M4 wifi board for my CPC6128 with Edge connector, could you send me details how to order it. Thank you.

    Reply

  70. Hi!
    I am also insterested in buying an M4 wifi board for my Schneider CPC 6128. Please send me details how to order it. Thank´s

    Reply

  71. Hi Duke!
    I’m fascinated about your M4 board.
    Will still be possible to get one to use it on my Schneiders? (CPC 664 & CPC 6218) I also have Amstrad CPC 464/472, but not sure if any additional hardware should be needed for those…
    Could you send me some details on how can I order one, please?
    Kind regards

    Reply

  72. Dear Duke,

    some days ago, after dedusting my Schneider CPC 464 and replacing the belt in my DD-1, i found out, that almost all of my about 30 year old disks still work fine, as well as my tapes do.
    Searching for a possibility so backup my old programs (from 1985 – 1991) to a more up-to-date medium with the option to copy it to a pc, I found your great project that may fulfill all my wishes. 🙂
    Now, before ordering one, I have two questions:

    First, is it possible, to use your board together with the DD-1? E.g. using the PCB adapter? Probably this was already answered somewhere, but yet I haven’t found.

    Second, long time ago I build a battery buffered memory for the 464. To connect it, I made a breakthrough into the housing of the DD-1 controller and soldered an edge connector on the back of the controller. Some kind of classical passthrough directly on the controller board.
    Do you think I can connnect the M4 board to the CPC using this connection? Or does the M4 have to come first for some reason?

    Due to the 90 degree solution, I am tending to order the M4 with MX4 connector and the pcb adapter. Please send me an email concerning that order.

    Reply

    1. It will work fine together with DDI-1. And I think it should work with your passthrough connector aswell, but yes my 90 deg adapter might be more handy and not dependant on the DDI-1.

      Will email shortly.

      Reply

  73. Hi Duke,

    I just found about your board, and I’m interested in buying one. Can you send me the details of how to order?

    Thanks!

    Reply

  74. Hello Duke,

    Could I have one of these wonderful boards for my Amstrad CPC 6128, please. Please let me know method of payment. I live in Sydney, Australia.

    Many thanks,

    Adam

    Reply

  75. Hey Duke!

    That’s an amzing thing you did there and I would love to order one M4 Board for my Schneider 464
    Vielen Dank für die grandiose Arbeit! Ich bin schon sehr gespannt!

    Sascha

    Reply

  78. Hello, I would be interested in a card assembled, if they are still available or when they could be. If it is the case, please I would ask for details about price, means of payment etc. I am writing from Spain.

    Reply

  80. Hey.

    Really cool device. I’ll take one for my CPC 464 if you run another batch. Thanks 🙂

    BR,
    Mathias

    Reply

  81. I also would like to buy M4 (or any other additional hardware you make) for Amstrad CPC464.

    Please email me…

    Prof. L

    Reply

  82. Hi Duke

    There seems to be renewed interest in more of the M4 boards

    and I’m one of them 🙂

    I’d be interested in a couple if you do a new batch

    Cheers and thanks for creating this masterpiece

    Reply

  85. Hi Duke. I’m from Spain and I’m interested in M4 card, M4 mother board and connection cables for CPC464. I wait your answer. Thanks

    Reply

  88. I’m also interested in buying one M4 if you’re running anothr batch.

    Thank you for your awesome work!!!

    Reply

  90. Hi Duke,
    How to receive a fantastic kit “M4 board” for a CPC464 and 6128 ?
    It’s a great job…

    castman.fr

    Reply

  91. Hi, I would like to buy a M4 board too, can you put me on the list ? Thanks a lot and have a nice day

    Reply

  94. Hi Duke

    I would like to buy another M4 board please. I have moved my existing one from my 6128 to my 6128 Plus (and it’s great on there), so would like a 2nd one for my 6128.

    Thanks
    Chris

    Reply

  97. I’m desperate for one of these boards too. I’m in the UK. Where do I sign up? Awesome work.

    Reply

  98. Hi Duke,

    I’d like to buy one of your M4 boards for the CPC 464 I just manage to acquire.

    Thanks,

    Roddy.

    Reply

  99. Hello,

    I’d like to buy M4 board too if still available for a trashed 6128 plus I saved last week and back to near mint state 🙂

    Reply

  101. Hi, this M4 board is just what I am looking for! Can you tell me how I can get one for my 464?
    Thanks 🙂

    Reply

  105. Hello,
    1st Thanks for the great work done on our old CPCs.
    2nd, May I ask you how I can buy one M4 Wifi Board?
    Regards
    Yann

    Reply

  107. Hi there,

    I would like to get one M4 board, latest pcb. I live in Greece. Can you please provide me info about cost, availability, shiping, payment method,etc?

    Kindly Regards

    Reply

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