Serial communication with PK-232

Hi, first off I think I can still call my self an Arduino newbie. What I want to do is have my arduino program talk to a PK-232. A PK-232 is a device called a TNC. TNC stands for Terminal Node Controller which is used for communicating with packet radio. Packet radio is a digital mode that ham radio operators use to communicate computer to computer or keyboard to keyboard. Now then, my PK-232 communcates over 9600 baud (or whatever I tell it) serial. To provide more info about the serial I will say that the PK-232 is currently connected to my serial port with a three wire connector I made(TX, RX, and GND). If you wondering what this will be used for, It's going to be an APRS weather station. APRS=Automatic Positioning and Reporting System. Go and find a weather station on the site thats what this is going to do but for now just temerature. Hopefully someone can help.

Thanks! Spencer, KJ6ART

Pretty straight forward application. The first issue you have to deal with is the voltage and logic inversion translation required to convert from RS-232 signals to serial TTL signals. You can either use a MAX232 type IC or even build your own convertor from simple parts. Here is one drawing:

After that is all software.

Good luck

Lefty (WA6TKD)

Ok, I think I'll build the circuit. For Q1 since I can't find a transistor called 3906 can I just use a general purpose PNP transistor same for Q2 but PNP? If not maybe you can find the Digi-Key part numbers for me. And for the VCC should I just tie that to 5 volts on the arduino? Does C1 have to be polarized? I would sure like to talk to you, do you have coverage for the Mt. Diablo W6CX repeater?

Thanks! Spencer, KJ6ART

Those transistor types are 2N3904 and 2N3906, probably the most common popular PNP/NPN pair around. If you can't find any local send me a PM with your address and I'll mail you a couple of each. Yes, Vcc is wired to the Arduino +5vdc pin and don't forget the ground wire to the Arduino.

Not active on the ham bands for some time now. 2 meter rig is in a box somewhere in the garage. However Mt. Diablo is an easy contact from here in that 4800ft above sea level reaches everything around the Bay Area.

Lefty WA6TKD

Two last questions, I guess I follow the schematic and put the TX and the RX pins on pins 0 and 1 on the arduino then I just use serial commands like Serial.print and does C1 on the schematic have to be polarized?

TX wires to Arduino connector pin 0 RX wires to Arduino connector pin 1 GND wires to Arduino ground pin Vcc wires to Arduino +5vdc pin

The 10MFD cap is an electrolytic cap and the positive lead does wire to ground as shown. You could use a non-polarized cap, but they are awful large (and expensive) in size compared to a simple electrolytic cap.the cap should have a voltage rating above 15vdc or so. The two LEDs shown are optional, but useful to tell when data is being sent and received.


Ok, I'm off soldering. Thanks for your help. 73!