Precise sensing of camera triggering for RTK geotagging

Hardware OSD/Video
1

Hey, there!
I´ve been struggling to use a Samsung Nx-mini with RTK.
It´s ~300ms delay to take a photo makes the RTK useless.
This camera doesn’t have a conventional hotshoe or other type of feedback which could be used to trigger the RTK camera input pin.

To solve this, it seems to me that identifying the moment when the camera starts writing on the sd card is the way to go.
Not the easiest solution, but the most universal and precise for the smaller effort.

So from what I gathered SD cards use a Serial Peripheral Interface. (SPI) (https://en.wikipedia.org/wiki/Serial_Peripheral_Interface#Mode_Numbers)

I don’t know how is the behavior of the communication, but I’m hoping that the Master Output Slave Input (MOSI) pin only sees activity when a picture is taken, and that the delay is smaller than 1ms after the picture is taken. Otherwise, identifying when it is really writing an image will get quite a bit harder.

Considering this, it might be possible to use interrupt routines to a pin connected to the sd card MOSI, identifying the write event and triggering the RTK. I’m looking for the simplest solution, a way to detect writing activity without disturbing the SD Card communication.

Any suggestions on the circuit between the sd card and microcontroller?
Any obvious problems I’m not seeing?

2

Hello Marco,

in most cases you will take the next picture in the write process of the first one…
Just getting a camera with a hotshoe seems a lot easier to me :slight_smile:

3

Hello!
Yeah, you are right! This would work for the first photo… only.
Problem is, I’m stuck with this camera for now. Mostly due to weight and space constraints.

I guess, for now, I’ll have to put a microcontroller receiving the trigger command from pixhawk and forwarding it to the GPS with a fixed delay. At least it will reduce the error.

Thanks!

4

Hi Marco, what method are you using to geotag in PPK?

Daniel B