Controling motor from msx

It would be much more easy to answer these questions, if you would tell what kind of "control" you want to implement. All the solutions depend of things like motor size and level of control.

If you need just one small motor that you can power on or off then the BASIC command MOTOR ON/OFF can be a solution... -> Wire power to motor so that is spins. Cut one wire and connect the loose wires to cassette port pins 6 and 7 and you are done. This is however not meant to control a washing machine or so.

Next easy (from hardware perspective) is to control servo motors. These are special in a way that they don't spin, but turn to angle you want. Power the servo with battery or other PSU. Connect data wire to some printer port data pin and ground to MSX ground. Load a BASIC driver (I can provide) and you are done. This way you can control up to 8 servo motors. Downside on this is that printer connectors are harder to find and the BASIC library needs that you run you MSX monitor on 50Hz refresh rate.

Demo: https://www.youtube.com/watch?v=JjabFEr_Jz0

If you need to contol motor spin speed & direction then likely it is good idea to check RC car parts. AFAIK many speed controllers take same kind of input than servos, so same library is likely fine, but check the speed controller specs.

If you want ie. just more of these ON/OFF controls or for bigger motor then look for Arduino examples or ready build accessories. If you connect the circuit to MSX printer port instead of Arduino, you are likely fine. On MSX-BASIC you can have direct control of printerport 8 data pins by using OUT &H91,&Bxxxxxxxx command.

Joystick ports are hard to control even with assembly and practically out of reach for BASIC programmer. They have also only 3 output pins, so you likely need more electronic ICs (ie. shift registers) to get any useful results. Only really appealing thing is that the connectors are easy to find.

RS-232 may also sound nice, but in practice it is likely not what you want. Many devices around us from DSL-modems to video projectors can be controlled with RS-232. There exists also all kinds of servo and motor controllers that you can buy. If your MSX happens to be ie. SVI-738 then it might be viable option to control these. How ever most MSX machines don't have built in RS-232 port but you need external one. Even when you get the physical port attached, you likely soon find out that it does not support BASIC at all... Even if all of this is sorted out, you need to think about communication speed & other settings and learn the control language, maybe add checksums etc. It can easily get pretty complex & far from the orginal goal, if your original goal was not very complex in the first place.

Just to cover all options, naturally MSX cartridge port is the ultimate solution "with no limits", if your goal is to do some really serious stuff, but that approach requires quite a bit more components and dedication.

Ok, I Googled and found this video:

https://www.youtube.com/watch?v=-f6FthqPwog

... seems that servo motors could work fine.

Here is kind of super simple example of what such solar tracker program could look like on MSX-BASIC: (Moves towards sun once in an hour and powers off servos for the night)

10 DEFINT A-Z
20 BLOAD"SERVO.BIN",R
30 GET TIME T$:H=VAL(T$)
40 IF H<8 or H>19 THEN X=0:Y=0 ELSE X=H*10:Y=SIN((H-8)/3.5)*50+50
50 A=USR0(0):A=USR1(X)
60 A=USR0(1):A=USR1(Y)
70 GOTO 30

Here is the control library:
https://msx.fi/temp/servo.zip

Documentation is on sources.

Well I was answering the OP so I didn’t read the 2nd page

Well almost this post could be a reference for someone else looking into motor interfacing or maybe if you guys decide to go the cartridge route.
Rogo one is basic but still requires some knowledge to build the cartridges and so but almost in the first link I point to other post where source files can be reached.
Second one (based over proto cartridge) will require also knowledge but almost the proto cartridge itself was conceived as help for those requiring cartridg slot interfacing with tinkering goals

Hope it helps somehow and forgive me for posting without reading the whole thread…

Ah, right... I missed this part... Well, in this case it is likely enough that you can drive two motors back and forth... You can for example plug this to your printer port: https://www.ebay.com/itm/355017150136

if you use pins D0-D3, this should get you going in BASIC:
Drive motor 1 forward: OUT &H91,1
Drive motor 1 backwards: OUT &H91,2
Drive motor 2 forward: OUT &H91,4
Drive motor 2 backwards: OUT &H91,8
Stop all: OUT &H91,0

You can also add these together, so ie. both forward = 1+4 = 5 -> OUT &H91,5