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Nixie
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Joined: 19/02/2013
Location: Australia
Posts: 66

Posted: 09:32pm 14 Apr 2014

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Greetings all,

I'm learning lots about Serial Comms and have two Mono MMs talking nicely to each other on COM1 using 3 wires.

Now I want to connect a Kenwood TH7D transciever, with a built-in Packet Radio Modem/TNC (terminal node controller), to my MonoMM. The Kenwood handbook says connect a computer running a terminal program with the following parameters: 9600bps, Data Length 8 bits, Stop bit 1, Parity none and Flow Control Xon/Xoff. For hardware it shows 3 connections to the serial port of a PC: transmit data, receive data and ground. (There are only three connections available to the Modem/TNC.)

So I have it all connected up; and went to COM1 with flow control....but I understood that you need 5 wires not 3 to use flow control? So should I strap the appropriate flow control pins to the Tx and Rx pins accordingly?

When connecting the MM, I should receive the prompt "Cmd:" on the screen....but I get gobbledygook...but at least it's the same gobbledygook each time. I've tried changing baud rates; the default is 9600 anyway, but didn't make any difference.

My Q&D test code is:

100 Open "COM1:9600, FC" As #1
200 b$=Input$(1,#1)
210 Print b$
300 Goto 200

Any assistance most welcome. many thanks, Nic.

VK3COW....on a remote cattle property in Western Victoria.....

TassyJim

Guru

Joined: 07/08/2011
Location: Australia
Posts: 6102

Posted: 09:48pm 14 Apr 2014

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Firt the flowcontrol.
XON/ XOFF is software flow control.
You ignore FC and the extra hardware lines and send chr$(17) for start (XON) and chr$(19) for stop (XOFF)

The gobblegook usually means that you have the polarity inverted.
You may need an inverter in the RX and TX lines between the MM and the TH7D
If the manual talks about connecting to a PC, it is very likely that you need the inverter for the MM. The low voltages of the MM might be a problem but not likely.

Jim

VK7JH
MMedit MMBasic Help

TassyJim

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Joined: 07/08/2011
Location: Australia
Posts: 6102

Posted: 10:28pm 14 Apr 2014

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Nixie,
I did a bit of checking on the TH7D.
It appears to have RS232 levels +-6V on the TX line so it is going to definitely need inverters. Either a MAX232 or a simple one transistor inverter will do. The TH7D should be happy with 0 to +5V on its RX line.

Jim

VK7JH
MMedit MMBasic Help

Nixie
Regular Member

Joined: 19/02/2013
Location: Australia
Posts: 66

Posted: 10:37pm 14 Apr 2014

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Ah ha! Thanks Jim.
Just been scratching round in my 'junk box' and found a MAX232, so that's a start!
Will try it out when I can!So appreciate the info.
73 Nic.

Nixie
Regular Member

Joined: 19/02/2013
Location: Australia
Posts: 66

Posted: 08:36pm 20 Apr 2014

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Easter slowed things up a bit... But just wired up the MAX232 chip up. You were spot on with your diagnosis! It now works a treat! Thank you !

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