On Sun, 12 Feb 2012 00:06:59 Dan Smith wrote:
I wonder if I need a diode between the Tx and Rx lines.
Nope, you don't. Just tie the TX and RX lines together and feed them to the radio's data pin. Make sure your data and ground lines aren't switched.
Open a serial terminal (like minicom) and start the clone from the radio. See if you see any data, especially like AH0XX. If not, there's no communication. If you do, but it's garbled, then search for a suitable baud rate. If you see AH0XX, then you're off to mess with CHIRP code.
Ok, I tried gtkterm with all available baud rates, from 300 baud to 115k, all with 8 bits and no parity. Nothing. I would have thought the baud rate to be well-known, but I can't find any information about it on the web.
The loopback still works.
I will try another 4-pin cable. And I will try a diode between Tx and Rx. It seems to me that the radio is trying to pull down the data line, but the PC Tx line is pulling up (idle).
I also wonder about using 3.3V. I measured the idle state of the radio's data pin and got about 3V. This made me nervous about using a 5V TTL interface, so I modified the FTDI board to use 3.3V. Many of the interface circuits on the web use 5V (or some hacked power supply from the serial port control lines). Perhaps I should go back to 5V. I will be making a 5V interface anyway, for the FT817ND. I will use the same 3.5mm stereo socket for Tx/Rx/Gnd and make up a cable to the '817 data connector.
73,
Andrew ZL3AME