An update is well overdue. I’ve managed to lose another post as well, but it was pretty much a ‘I’m still on with it’ post. I had a hard lock up whilst running the TERMINAL program and couldn’t clear it with the RESET button, so I had to pull the batteries and switch off the backup battery thus clearing the memory of all files.
I was waiting for a dsub-25 male connector to arrive in the post up until a couple of days ago as I couldn’t get a cable made up with the various connectors I have lying around. As you can see from the photos attached to this post I decided to use a piece of breadboard to try and determine the correct connections for the RS/232 cable. Initially I tried a full hardware handshake cable, but I think I’m missing the mark of what I need.
I have got comms working between the ESP8266 module and the Tandy 200, but it’s far from perfect. Even at 300 baud I’m getting characters dropped. Having looked at various version of null-modem cables I’ve come to the conclusion that I’m going to have to implement software flow control within my ESP8266 lua program. For some reason I was missing the obvious issue that the MAX232 module I’m using is only connected to the ESP8266 module with TX/RX lines, so there is no way in which this end could implement hardware flow control.
The issues I’ve had with the Tandy 200 talking I think are down to the fact that the Tandy does require hardware flow control to be implemented even if it’s a case of looping back signals to satisfy Clear to Send/Ready to Send.
Next steps then are to look a bit more in to hardware versus software flow control and implement XON/XOFF in my telnet client on the ESP8266.