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Raspberry Pi Pico Lanc controller - Weird transistor issue

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AshW:
Hi everyone!

I'm following the following article to create a LANC controller using a Raspberry Pi Pico (Running Arduino) http://controlyourcamera.blogspot.com/2011/02/arduino-controlled-video-recording-over.html

Unfortunately it only works while using an external +5V source or when any lead of the transistor / Lanc out pin is disconnected and reconnected while the camera is powered on as it appears the Transistor is pulling the +5V Lanc communication line low. As the line is pulled low the Pico is also unable to boot until either an external voltage source is connected or transistor lead disconnected and reconnected.

Am I missing something about what is happening with the transistor when it is pulling the line low when not using external power?

(I can also send the .sal or .csv from the logic analyser)

Thanks!

wasedadoc:
Please clarify. A RPi Pico is not an Arduino and does not "run Arduino". Yes the Arduino IDE can be used to compile code and upload to a Pico.

The schematic you show, copied from the original article, is not for a Pico. That article is dated 2011, almost a decade before RPL released the Pico.

pcprogrammer:
The schematic is for a 5V development board, which mostly means an Atmel based micro. The Raspberry pico is a 3.3V based development board and does not like 5V on the IO pins.

To be able to use it with a pico you have to modify the schematic so that the feedback signal on pin 5 (D11/PWM) is not directly connected to the LANC signal. It depends on the speed of the signal if you can use a resistor based divider or need an active level converter for it. Also the power input to the pico module needs to be looked at. Not sure if it can take more then 5V on VBUS.

Easy solution is to just get a regular Arduino nano or micro and build it with that.

tooki:

--- Quote from: wasedadoc on January 29, 2023, 06:49:49 am ---Please clarify. A RPi Pico is not an Arduino and does not "run Arduino". Yes the Arduino IDE can be used to compile code and upload to a Pico.

--- End quote ---
…and when you do that, the Arduino core runs atop the Mbed RTOS that the Pico runs, so it’s very much correct to say that it “runs Arduino”. Also, you can program the Pico with the Arduino framework without using the Arduino IDE (for example, with PlatformIO).


--- Quote from: wasedadoc on January 29, 2023, 06:49:49 am ---The schematic you show, copied from the original article, is not for a Pico. That article is dated 2011, almost a decade before RPL released the Pico.

--- End quote ---
Which doesn’t really matter much, except for the IO voltage problem (which would affect 3.3V Arduino-branded boards, too).

AshW:
Thanks for your help everyone, Tooki is correct. I am also using the exact schematic from the control your camera blog post but with a pico instead of an Arduino. Only after I tested it did I realise the pico wasn’t 5V tolerant but THE CIRCUIT DOES WORK! (For the most part).

Currently I am having a new issue where unless my logic analyser (knock off 1st Gen salae logic) is plugged into the recButton port the circuit will continually trigger as the recButton like is pulled low. When hooking up the logic analyser to the recButton the line is pulled to 3.3V (as seen on an oscilloscope). Adding a 100nF decoupling cap hasn’t helped either. I apologise for my explanation but I don’t see how the logic analyser could be affecting this.


I apologise if any of my terminology or explanations are insufficient as I am new to programming microcontrollers.

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