trouble using multiple com ports Zx 1280

[abergum]

I'm working of setting up my J26 port on my ZX-1280 board to communicate to a thermistor module while com1 spits the data back to my computer. No matter what I do I cannot seem to get the second serial port working from J26 and have not been able to find any reference to this in the ZBasic ref or library. I've been playing with all the ComChannel and DefineCom commands and do not understand what I am doing wrong. Looking at the schematic it appears the transmit and recieve pins at J13 might need to be jumped to other pins on the board, possibly D.3 and D.4 in port J4?? My computer communication through com 1 has been flawless, but my simple string out code I'm trying to put out com2 will not do anything. Please help.

Andrew

[dkinzer]

I've been playing with all the ComChannel and DefineCom commands [...].

The ComChannel() routine only affects software UARTs. In most cases, the DefineCom() routine is only used for software UART channels. You can take both of those calls out.

Looking at the schematic it appears the transmit and recieve pins at J13 might need to be jumped to other pins on the board, possibly D.3 and D.4 in port J4??

Just so, as described in the manual:

J13
This two-pin connection provides access to the TTL-level transmit and receive signals for the J26 serial port. The transmit signal is applied to an RS-232 level converter whose output is connected to pin 2 of J26. Similarly, the RS-232 signal on pin 3 of J26 is applied to the level converter and the corresponding TTL output is available as the receive signal.

The reason that the RxD and TxD pins of the RS-232 level converter are not connected to a particular pair of pins is that there are many choices (Com2, Com7, Com8 - which all have specific RxD/TxD pins; and Com3-Com6 where RxD and TxD can be assigned to any general purpose I/O pins). For Com2, the connections required are D.2->RxD and D.3->TxD.

[abergum]

Awesome, I have it working now. I was going off the schematic in the ZX-1280 Reference Manual which looks like it calls pins D.3 and D.4 connecting to the Rx and Tx of J13. When I tried pins D.2 and D.3 (as it says in the Hardware UART Channel Assignment chart in the system library which I should have checked) jumped to J13 everything came together.

Thanks for the patience and help of a newbie.

Andrew