22 Jan
2016
22 Jan
'16
6:04 p.m.
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.