Re: [Paparazzi-devel] 5v pulse required for CHDK on Lisa/M2

[Gerard Toonstra]

Thanks for the help. So this breakout would probably work?

https://www.sparkfun.com/products/9118

I've also noticed that the default signal for the dc cam module is (3.3V) by default and switches to 0V when triggering, where I'd expect the opposite.
Can you elaborate on the reason for this?

Rgds,

Gerard

On Fri, Nov 2, 2012 at 5:30 AM, Hector Garcia de Marina <address@hidden> wrote:

Agree with the last solution of Christophe. It would be desirable using an optocoupler for keeping cleaner the GND for the analog signals especially.

On Fri, Nov 2, 2012 at 9:07 AM, Christophe De Wagter <address@hidden> wrote:

Use e.g. a 2k to 20k Ohm resistor connected from USB+ to 5Vusb to pull it up. Use any N-MOSFET transistor (e.g. bss138) with its Gate to any paparazzi IO pin, its Source at Ground and it's drain at the USB+ pin, pulling it to zero when the io pin in paparazzi is higher than 0.7 volt.

If you have no Fet but have a bipolar NPN transistor around (like a bc547) then you just need 1 extra resistor of about 10x more ohm in between the paparazzi board and the NPN.

Another solution we use most of the time is a bipolar optocoupler switch instead of a MOSFET. Then there are no copper connections between the noisy camera ground and the autopilot/GPS/modem ground for optimal telemetry and gps signals.