Originally posted by lister6520 The card itself does not need to know anything about tethering and all the camera needs to know about WiFi is how to use it to transfer information to/from another device without needing to understand the data it is transmitting. 99% of that is standard Wifi/Inetrnet protocol and the remaining 1% is the specifics of how the camera communicates with the card.
I don't agree with that.
Most -- or maybe all -- Wifi SD cards to date are capable of one primary function: identifying new image files on the memory card and using the network to send them somewhere (an attached mobile device, or the Internet via a router, or whatever). The card handles that communication protocol including all the handshaking necessary to accomplish the wireless data transfer.
This isn't a simple process, so by necessity these cards are tiny little embedded computers themselves. On at least one brand of wireless SD card, it's possible to hack into the system and
run your own commands on its own little Linux-type shell.
At the moment, I don't think any other wireless card is programmed to receive CAMERA COMMANDS (set exposure values, focus, shutter, etc.) from a remote device, interpret them, and them send them through the SD interface to a camera that is capable of handling them. And at the same time, to stream the live-view image from the camera at a satisfactory resolution and frame rate. Part of this involves the card confirming that the camera is a Pentax K-3 that can receive these commands, so it doesn't twiddle interface bits in a way that would cause another camera to throw an error.
I suspect all of this is accomplished via firmware in the card, running on its tiny little embedded processor. And I also suspect that the FLUcard people -- being far from market leaders -- were the ones who were willing to "play ball" with Pentax on a custom card, or at least the ones who made the most favorable deal.
I really do think there is extra programming in the card to enable this tethering. It's probably just firmware, but at that level, I think it must be a custom card.