My goal is to create a tiny standalone MP3 player that can start/stop and pause with just hardware triggers no programming and no controllers. I am using the Qwiic MP3 Trigger board to do this.
Before I start trying to solder directly onto pin 13(!!) are there any alternatives to trigger the ADKEY functionality on the onboard WT2003S MP3 decoder IC or indeed other products available to achieve the goal stated above?
PS I have considered the larger and more expensive MP3 Trigger but its too big
We’ve never tried using this product in that manner before, but looking at the data sheet, you might be able to get it to work. (You would need to try it and see.)
The only potential issue I’m seeing is that the resistance value the datasheet calls for to do Play/Pause is zero ohms and using that according to their schematics, would cause a dead short between VCC and ground. That would not be an ideal situation and could cause damage to the board. I suspect that’s an error in the data sheet, and I wouldn’t use any resistor smaller than 10 ohms there. You may need to experiment with different values for the Play/Pause key to find what works best assuming key control mode will work with this board.
There isn’t a great place on the board to access the ADKEY pin on the chip, but there is a solder pad next to a resistor that should work. It’s labeled in the picture below.
Yes, the schematic looks wrong. I think the idea is to pull up adkey with a 10k resistor and have the buttons connect adkey to ground through a resistor (0 ohms, 1k, 2k, and 10k respectively). This will act as a voltage divider and the WT2003S will measure the voltage on adkey to decide which button has been pressed.
Also, the pin that TS-Chris is showing with the arrow does NOT look like ADKEY (it looks like VCCIO instead). I think ADKEY is the other end of that resistor. For a quick test try shorting the other end of that resistor to the pad of the capacitor right above it (ground).
Thanks for the replies. I am working with basic school knowledge here so forgive any obvious questions going forward!
‘pull up adkey with 10k resistor’ - does that mean just connect it via a 10k resistor to the same 3.3V input as the board? ie Pin 13(ADKEY) → 10k resistor → 3.3V
what does the resistor mentioned above that is next to the ADKEY pin do? I have indadvertedly removed it whilst trying to solder to the adjacent pad. Is there a board diagram anywhere?
The board still plays a track and I have now attached a lead directly to the pin on the chip with more success, although now I dont know if the results of my tests are affected by the lack of the other resistor or not.
Breaking out that pin would be great in the future. As I see it that would add play/pause, volume±, track ± functionality for little (?) overhead.
Yes, the 10k pullup is a 10k resistor from the pin to 3.3v (called VCCIO in the schematic). It serves two purposes - to have ADKEY sit at 3.3v when no button is pressed, and as the top half of a voltage divider (the bottom half is the pressed button and the resistor from it to ground) when you press a button.
If you go to the “documents” tab on the QWIIC MP3 Trigger page, you will find the schematic as a PDF, and the Eagle source files, which you can use with the free Eagle software to view the PCB layout.
