My dual purpose (USB/RS232) cable
from Nikon Coolpix 880 USB cable

CAUTION !!! There is no guarantee about everything written in this page. All the schematic (pinning ...etc) come from my, Per and David measurements and analysis. Our Nikon connector numerotation is probably far away from the Nikon one...
Use this procedure described below at your own risks ! I suppose Nikon would not recomand it.

Per and David are persons that i met on the DP review forum on that subject (see the specific thread).
Per develop a software to drive Coolpix from a PC. You can visit his web site.
David was the first to modify his cable, you can also visit his web site.or this other version of it

Because Nikon serial cable is expensive and very hard to buy (delay are very long), i decided to build my own serial cable from the USB delivered with my Coolpix 880.

1- First step : removing plastic

It's quite easy with a little knife (very well sharpened), but be carefull because wires inside are very very small and easily destroyed. However i succeeded without having to unsolded USB wires.

Remember : You need to be very precise because the connector is very little !

2- Second step : Soldering 4 rs232 wires on the unsolded tags

The Nikon connector pinning as described on the David web site.

On the schematic below, red connection (USB) already exist inside original Nikon cable, blue (rs232) should be added.

Remarks :

• The Coolpix camera detect a PC connection when pin 2 (on nikon connector) is connected to shield or gnd line. I call this line "gnd_ctrl". With the schematic above, this connection is done when the rs232 connector is plugged inside port COMx of the PC. (shield is connected to gnd inside the computer)
• If an rs232 extension cable is used between "my" cable and the PC, this extension should have a shield connected on both side. Otherwise the camera won't detect any connection. If your extension cable have only 3 wires without any shield, connect shield to gnd line on both side (my extension cable is build like this).
• I suppose that USB connection is detected by the camera when vcc is applied to the right Nikon connector pin, this hapen when USB connector is plugged to PC. CAUTION !!! When you choose your connection (USB or RS232), keep the other connector unpluged. USB connector and RS232 connector should not be plugged together to your PC. Otherwise the camera will perhaps switch on both USB and rs232 hardware and i don't know what could be the consequences. (and i don't want to try...).
• Pin 5 and shield are connected together inside the coolpix.
• I decided to sold gnd line (black wire below), not only on pin 5, but also on the Nikon connector shield. I think now that it's not absolutly necessary because pin 5 and shield are connected together inside the camera.
• Be carefull to choose a very flexible cable to avoid mechanical damages of the camera connector. I choosed to have a short length on rs232 path to avoid too much embarrassment when using USB connection.

3- Third step : Covering it

To protect all the tags and soldering, i used some thermic slipcover (on the right side of the 1st image below).
The diameter of this thermic slipcover has the property to decrease with heat.
On my cable, i used 3 layers of it.

Conclusion :

Since this modification, "my" cable is still functional for USB connections, but now also for RS232 connections. It work correctly with Nikon View 3.1 (configured to use port COM1) and my 5 meter extension cable (no shield inside).
Images transfering speed with this cable seems to be classic, see below :

• Serial (COM1 @ 115200) : 9.7 Ko/s (77660 bits/s, 70% of theorical speed)
• USB : 0.3 Mo/s (308710 bits/s, 30 times quicker than serial speed)

Enjoy !