[SOLVED] Send "T" character through the camera's USB port

[surami]

Is it possible to send a "T" character through the camera's USB port with a proper USB cable to trigger the MX2 controller?

Please take a look at the TimeScapes forum, I'm not at home at this kind of engineering things.

I ask this because I would like to trigger the MX2 as the shutter closes, but my camera's hotshoe + Pixel TF-321 + PC sync cable isn't working well, the triggering happens as the shutter opens.

[surami]

I think I have to explain, why I would like to use this kind of function.

I would like to give motion to my day to night sequence. It's not problem if I only use the ML's ETTR function (always on) with slowest shutter 8 sec + MX2 interval time to 10 sec. (Shoot -> Move -> Shoot). But this settings aren't enough for a really cool day to night (many stars) sequence, a 25 sec exposure should be needed at max ISO 3200, F2.8 (the 550D has not a world champion sensor, so this ISO is also too much for it, but anyway) and the motion shouldn't happen in that time when the shutter is open.

In theory the right way would be to use the ML's intervalometer (eg. 10 sec) + ETTR always on (slowest shutter 25 sec) + 2 sec. delayed exposure (Canon setting) + MX2 with external intervalometer setting. Why this settings? Because:
- 10 sec interval is quite good for a sunset + the ETTR will expand this time as needed for a proper ETTR picture at night
- 2 sec delayed exposure is needed to save the picture, set up automaticaly the new ETTR settings and give enough time for motion before the next circle
- ML should send a signal to the MX2, that the motion should happen right after the shutter closes

[ansius]

first, sure you do not understand how USB works on camera and mx2, on mx2 it emulates com port, and usb as such is ment device <=> computer, with few exceptions like printing. so the short answer - really hard to do, if not impossible.

second - I'm not sure how the 550D hotshue works but as much as I know, it should be shorted while shutter is open (that is how my 40D and 7D works) thus, connecting it to mx2 you should use this signal not to trigger motion on front of impulse, but back - falling edge. I do not know exact settings of mx2 because I do not have one, just using my experience with other logical controllers. you should either ask mx2 guys the help setup it so that motion is triggered on end of the pulse, ask it maybe on the timescapes forum, or if that fails - you could electronically invert the signal, but that is rather hack than a normal solution.

[surami]

OK, then let's forget this USB trigger thing. Yes, I don't know what's possible and what's not through USB port. I just asked, because my camera + hotshoe mounted PC sync cable + MX2 I/O port chain isn't working properly. I set up everything as MX2 guys told (there is an option what you wrote, invert I/O, it's needed), but sadly the triggering isn't happening in the right time, it works the same way as the I/O port wouldn't be inverted.

I tested (as Jay suggested from Dynamic Percepton) the PC sync cable connected to the MX2 controller's EXT1 port (I/O 2 external invertvalometer + inverted I/O setting) with shorting the sleeve and tip, so I could simulate long exposure with holding the circuit closed. As I opened the motion triggered imediatly, the cable is ok. So wether that Pixel TF-321 stuff or my camera isn't working properly. I will order next week this kind of Hama hotshoe PC cable stuff.

[Pelican]

Have you ever tried to set rear sync flash on your camera?
If you set rear sync, the hot shoe fires about 1 ms before the shutter closes, so maybe you can use that signal for your need.

[ansius]

So wether that Pixel TF-321 stuff or my camera isn't working properly. I will order next week this kind of Hama hotshoe PC cable stuff.

maybe try to clean the contacts, I've noticed that when my cameras have been used longer time without external flash, socket tends to oxidize, not much, but enough to be unstable, signal break would not trigger a flash (as it is triggered at pulse front), but would be enough to trigger mx2 when contact is lost momentarily.

[surami]

@Pelican: It's very good idea, but I couldn't setup things in the menu Flash control/External flash func. settings earlier because as I entered into the menu, this was what i saw: "This menu cannot be displayed. Incompatible flash or flash's power is turned off."

@ansius: Thanks for the advice, I will clean the socket.

Yesterday evening I disassamled that TF-321 hot shoe stuff, because I thought there is too much connections (5 in the middle and 1 on sides) to the camera's hot shoe mount and the connections should be reduced, maybe this could cause signal lost or I don't know. I thought this because that Hama stuff has only 1 connection in the middle and 1 on the sides. (topside, bottomside)

Now my Pixel TF-321 is dead, because I operated on the stuff too much... I'm amateur and curious.

We will see what happans on the next week or as soon I can get a Hama hot shoe stuff. I hope a simpler hot shoe stuff will do the job.

@ML developers: Is it possible to implement a delay option into the Auto ETTR mechanism? Maybe that 2 sec delayed exposure is too weak for saving the picture, calculate the ETTR things and for the motion.

[surami]

Solved!