FTDI setup, imprecise description

General Website and Documentation errors
1

Hi guys,

I try to communicate with the Pixhawk Serial4/5 by using the FTDI.
I saw this picture and I think it is wrong:

Pixhawk_FTDICable_NSH.jpg1264×552 49.5 KB

from: http://ardupilot.org/dev/docs/interfacing-with-pixhawk-using-the-nsh.html
If you look at the DF13 connector in the picture, it says that this is the setup for Serial5.
But if you look at the schematics and compare it with this picture then it is hooked up to Serial4.

Picture:
FTDI-Cable (top down):
GND
CTS
VCC
TX
RX
DTR

DF13 (top down):
VDD
Serial4TX
Serial4RX
Serial5TX
Serial5RX
GND

According to the picture and compared with the schematics, the FTDI-Cable is hooked up like this which would be completely wrong:
GND-------------GND (OK)
Serial4TX------RX (???)
Serial4RX-----TX (???)

So how do I need to hook-up the FTDI-cable now?

Thanks.

2

I found this:

SERIAL 4/5 port - due to space constraints two ports are on one connector.
Pin Signal Volt
1 (red) VCC +5V
2 (blk) TX (#4) +3.3V
3 (blk) RX (#4) +3.3V
4 (blk) TX (#5) +3.3V
5 (blk) RX (#5) +3.3V
6 (blk) GND GND

http://ardupilot.org/copter/docs/common-pixhawk-overview.html

Is this correct? What means blk and red? I cannot see any black or red on the Pixhawk.
Where is PIN1? Next to the reset-button?

3

Pin 1 is inside eg. +5v and GND is close to the edge of the board. For hooking up FTDI cable, use TX/RX and GND pins. For TX/RX pins it does not matter which way you put them, you won’t break anything. If you have them wrong way you just don’t get any data and in this case just swap TX/RX pins and you should start to get data flowing.
Easiest it is to test with Terminal software or similar. In generally TX output goes to RX input and vise versa.
Black/Red is referred on the original cables as red is always where +5v is.

4

Thank you. It works now.
I thought I need to connect RX with RX and TX with TX but this is wrong. So I connected RX with TX and TX with RX and now it works.

5

It most cases these days when connect a serial port you need to swap. I.e. TX transmit goes to RX receiver pin.

The docs says Serial4/5 port so are correct.

6

Hi, does it also work if I use Serial4 ?

7

You need to set the Params for the ports behaviour. For example if you want to connect using MAVLink on serial 4. Or a second GPS.