Casio EXILIM EX-ZR300 "external keyboard"

I needed remote control for my EX-ZR300 camera, and creating of an external keyboard appeared to me as the easiest way how to realize it. I decided to sacrifice the HDMI output and use some contacts of the HDMI 19pin connector and, using HDMI cable, connect the external keyboard this way.

Exploration of the camera buttons showed that 9 wires plus ground wire are enough to control 9 buttons plus zoom and two-step shutter button. Except for ON/OFF and HS buttons, all other buttons now have its external equivalent connected over cable. I used HDMI pins originally designated for data (6), clock (2) and one reserved pin. Data and clock signals were disconnected, so HDMI output is no more working on this camera. Basically all I needed to do was to break original HDMI signal connections on the mainboard and solder 9 wires from HDMI connector to points, where button connections comes to the mainboard. Those points are leads of FPC connectors, which have pitch 0.6mm, HDMI connector leads have pitch 0.4mm. This is the real challenge!

When the mainboard is observed by naked eye, it seems impossible to solder any wires securely without making any unwanted short circuits. When observed by magnifying glass, it seems even easy. The reality is somewhere in the middle. No doubt it is impossible to do it the usual way, with the solder iron in one hand, holding the part being soldered by other hand. Especially if one of the soldered parts is a wire, which has tendency to move and rotate about all axes. The soldered parts have to be fixed in advance. That's why I used small printed circuit board, I soldered wires (fixed in advance by two turnings around the board edge), then I fixed the board to the camera mainboard, and only than I soldered its 8 connections.

Now I think it was unnecessary complicated. The easiest way I have found at last is to fix the wire by kapton adhesive tape. This polyimide tape and its silicone adhesive withstands high temperature and it can be removed without leaving any residue.

When the wire is fixed, droplet of flux (rosin dissolved in ethanol, in the picture already dried up) and chip of solder is delivered to the place of the future joint. Then, with the magnifying glass on eye, with elbows on the desk, holding breath, is possible to try to heat the joint by solder iron, hoping that the attempt will be succesful. I use self-made soldering tip from aluminium alloy, where the tip itself is 0.4mm thick copper wire, wrapped tightly around the aluminium part and passing throught the hole in its axis.

Of course, the soldered wire has to be carefuly prepared. I used enamelled wire 0.08mm (about 0.09mm including insulation). I prefer mechanical removing of its insulation, but it is delicate work. I use fine sandpaper and some self-made gadgets. When the wire end is tinned, I shorten the tinned part to about 0.4mm. In this manner, it is uncertain, where the boundary between insulation and solder will be created, so I had to leave some spare, and that's why there are those loops of wire. The wires was finally fixed by cyanoacrylate glue.