MSX WiFi via RS232?

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By dmr

Rookie (30)

dmr's picture

15-03-2020, 19:35

Good to hear, thanks a lot for sharing this info.

The reason for looking at an ESP12/ESP32 is because the ESP8266 only has 4 I/O ports of which only two can be used fully, so that leaves only a UART solution to interface with it. And my goal is to skip the UART and connect the ESP directly to the databus of the MSX. That's why I think about using ESP12 or ESP32.

I have already done this with an Arduino, using a 74HCT688 for decoding the I/O-port together with IORQ/WR/RD signals triggering an interrupt at the Arduino after which it will read or write the data from/to the bus (connected via a 74HCT245). A0, A1 (and A2) can then be connected directly to the Arduino to implement multiple I/O ports (e.g. what you have as STS/TX and CMD/DataIN port).

I think this "trick" must be possible also with an ESP. The driver implementing UNAPI can then be similar to your approach: directly sending UNAPI commands to the ESP. The buffering that is done in your case in the UART (2K bytes) can be handled in the ESP in my case.

Just a few thoughts... I have yet to implement it ;-).

Looking forward to exchange ideas with you. Thanks again.

By ducasp

Master (238)

ducasp's picture

16-03-2020, 13:58

Yes, it should, not sure if the performance is going to be as good, as the ESP doesn't treat the IO's as a databus if I'm not mistaken, so you would still need to read each bit per bit if my assumption is right, and also you will need to program an interrupt for the "Interface Selected", which might get things a little bit more complex. Also you would be responsible for buffering and handling the IO from ESP32 to the MSX, which can be a little troublesome.

P.s.: one important aspect is to implement proper BUSDIR on your interface. The SM-X "MSX Interface" doesn't have this as it is internal to the FPGA and thus there are no bi-directional buffers to control the direction, but if you think of MSXs that have a slot expander or internal buffers, this might be really important otherwise the data sent might not be read by the CPU, that will read garbage....

By dmr

Rookie (30)

dmr's picture

24-03-2020, 23:11

bas.alicante wrote:

That's excellent! I'm not good at electronics, but I'm going to try and follow along with my MT-TELCOM II. Should work too, right? I've ordered the wifi module (which should take a couple of weeks to get here) and in the meantime I'll keep an eye on this thread and your github. Thanks for posting this!

Have you been able to put the ESP and the Telcom together? My Telcom II works with the ESP, however only from a (built-in) terminal program. As far as I know, the Telcom II is not supported by the fossil driver (at least not the version I have). Not very useful, but still fun.

It may be feasible to make the ESP do kermit,xmodem or zmodem... to support downloads. I have also looked at code that does support the Telcom, but it seems it is totally different from a Philips NMS12xx and other. Even though it uses the same Z8530.

BTW I am also working on a home-made cartridge to connect the ESP directly to an I/O port, using a few 74xxx chips and an MCP23008 (I2C 8 bit I/O expander). I need some time to finish the hardware and check if it works. If I have some results I'll open a new forum thread (as it is not RS232 based ;-) ).

By ducasp

Master (238)

ducasp's picture

25-03-2020, 22:29

dmr wrote:
bas.alicante wrote:

That's excellent! I'm not good at electronics, but I'm going to try and follow along with my MT-TELCOM II. Should work too, right? I've ordered the wifi module (which should take a couple of weeks to get here) and in the meantime I'll keep an eye on this thread and your github. Thanks for posting this!

Have you been able to put the ESP and the Telcom together? My Telcom II works with the ESP, however only from a (built-in) terminal program. As far as I know, the Telcom II is not supported by the fossil driver (at least not the version I have). Not very useful, but still fun.

It may be feasible to make the ESP do kermit,xmodem or zmodem... to support downloads. I have also looked at code that does support the Telcom, but it seems it is totally different from a Philips NMS12xx and other. Even though it uses the same Z8530.

BTW I am also working on a home-made cartridge to connect the ESP directly to an I/O port, using a few 74xxx chips and an MCP23008 (I2C 8 bit I/O expander). I need some time to finish the hardware and check if it works. If I have some results I'll open a new forum thread (as it is not RS232 based ;-) ).

That should work quite fine, I know of someone doing similar stuff with an ESP8266 (but the chip, not the modules using the chip) that should hit the streets soon. Wink As you plan using ESP32 instead, that could be potentially pretty fast as well as being able to handle more than one TLS/SSL connection at the same time. Wink

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