[chirp_users] FT7900r programmer

Jon GrosJean jgrosjean at ieee.org
Fri Jan 22 18:04:54 PST 2016


I am going to make a FT7900r programmer using an FTDI-1232 board which can
be set for 3.3V or 5V logic level.  The FT7900r uses 5V logic.  There is an
internal 4.7k pull up resistor on the PTT line, so an external pull-up is
not needed.

My question is about the data polarity.  The DL8WA board inverts the RS-232
data on both receive and transmit.  Maybe the person writing the program
wrote it to work this way.  Should I invert the outputs of the FTDI board
when used with CHIRP?  If not, a simple diode could be used on the TX data
output to pull down the PTT input.  If everything should be inverted, then
a couple of transistors could be used.

I will make my circuit available when finished.
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