RAK19026 (Wismesh Pocket v2) + RAK18001 Buzzer

Hi!

Recently purchased the Wismesh Pocket v2 for Meshtastic and decided it could use a buzzer so I got the RAK18001. But it’s not straightforward how to set everything on Meshtastic! There are several posts on the buzzer overheating, warnings on the RAK18001 documentation on setting things on LOW. Given that the Pocket v2 is suposed to be for newbies/dummies, I just want to make sure I’m doing it correctly.

Also found out that purchasing the RAK18001 doesn’t come with mounting screws, which after some reading, seems to need the M1.2 - 3mm (and given that this is for a flat board, the bottom of the screw should be flat?).

My goal is for this post to be a go-to for adding the buzzer correctly, so I’ll try to edit this post as needed. But please help out!

  1. Take apart the wismesh pocket v2 by unscrewing the 4 bolts.
  2. Identify the RAK19026 VC base board and the sensor slots C and D.
  3. Orient the RAK18001 buzzer so that it will snap onto the 24 pin connector.
  4. Gently press the RAK18001 onto the RAK19026. There should be a click / snap.
  5. Secure the RAK18001 with the M1.2 - 3mm screw.

Okay this is where I get confused, and I definitely don’t want to burn anything.

Depending on which slot chosen, the GPIO pin could be different?

Slot C is IO3, GPIO pin 21?
Slot D is IO5, GPIO pin 9 ?
(Taken from github repo, WisCore_RAK4631_Board/variant.h, another post)

Also what does it mean to set the PWM pin to LOW after playing a sound? How can I do this via Meshtastic app?

This is my first venture into these circuits, but what is the difference between PWM1 (where it has “NC”) and PWM2 (with the 330 ohm resistor)? RAK18001 documentation page also talks about swapping the terminals, which then I would have different IO numbers (slot C would be IO4, pin 4; slot D would be IO6, pin 10). I apologize but the last time I played with circuits is back in engineering school a few decades ago with breadboards, wires, chips with simple circuits. I clearly did not go into EE.

Welcome to the forum @Broom4270

We do not develop or maintain the Meshtastic firmware, so we cannot answer questions related to

  • “how does Meshtastic use the buzzer”
  • “how to set the IO pin in Meshtastic”
  • “does Meshtastic pull the GPIO to LOW”
    These questions can be answered by Meshtastic.

General answers:

Your assembly steps for the RAK18001 buzzer on the RAK19026 Base board are correct.

For the IO assignment, your assumption is correct.

Difference between PWM1 and PWM2 pin.
By default PWM2 pin is used to control the buzzer. In case there are IO conflicts with other modules, the module can be modified to use PWM1 instead.

Important:
On the RAK19026 Base Board, you have to use Slot C and IO3/GPIO 0.21. The GPIO on Slot D is already used by the user button.