A few questions around hardware

[lucas14145]

Hi, thanks for sharing all that work. This project looks really cool.

I was wondering before I order all the parts: Is it the final version of the pcb? What pololu 5v booster are you using? What about this capacitor next to the power button, no need for it?

I hope this is the right place to ask questions.

[jerry20091103]

Thanks for being interested in this project!

The PCB works fine. It will function just like in the video. The 5v booster is U1V11F5 from Pololu. But any 3~5v to 5v 1A boost converter should work. That capacitor is optional. Omitting it should not affect anything. The placement is awkward too...(It blocks the key)

However, the hardware is first-gen and there are some known issues:

• Some parts are a pain to solder (the type c connector, IO expander chip...)
• The boost converter does not have enough juice for the built-in speaker amp. So the audio distorts at high volume. (other outputs are fine though.)
• The power button is extremely easy to get at. It may turn itself on in a backpack.
• The two LED bars on the left are currently unused and will be removed in later versions.
• There's no place to properly mount the built-in speaker.
• The 3.5mm jacks are a little hard to find.
• There's a "pop" noise in the headphone output at startup.

I'm currently focusing on the software, as there are lots of features yet to be implemented. Once all the major features I wanted are finished, I can move on to hardware improvements. I think it will come no earlier than this summer...

I would really appreciate it if you build it and share feedback (or even add features) with me though.

[lucas14145]

Thanks for your answer, I'm looking forward for updated on this project. Yes I will definitely let you know if I build it. For those two led bars they looked super cool but not so easy to source and expensive plus it save quite a lot of soldering anyway. I see no batterie protection IC on the circuit is it on purpose? I have not much knowledge on electronic but I remember using one on a small batterie embedded project that I made...

[jerry20091103]

I use Li-po batteries with protection boards built-in. They are quite common, like this one https://www.adafruit.com/product/258 The small PCB on the top is the protection circuit. This is probably safer than implementing a protection circuit by myself... ;)

[VilhoKn]

Hi, I really like the whole design but had couple questions about it.

What speaker are you using? Have you thought about any solutions for the speaker amp distorting? (having a speaker is important for me) How are the usb D- and D+ connected to the teensy?

I'm a beginner and don't have a lot of experience with electronics but hope to learn more.

[jerry20091103]

Hi,

• One quick fix for the speaker distortion problem is to swap out the Pololu U1V11F5 5V booster for a higher current one. I do plan to upgrade the amp chip, but that would hopefully happen in the next hardware revision.
• Any 4-ohms speaker with at least a 3W power rating should work fine. Choose one that fits in the enclosure.
• The Teensy does not have pin headers for USB. It uses small solder pads right under the USB port. Solder two wires from the pads to J7 on the PCB, to connect D- and D+. (image from PJRC website)

Thanks for being interested in this project!

[lucas14145]

Hi Jerry, I'm slowly gathering the components to make one for myself! Right now I have the teensy 4.1 and the audio shield , the screen is on it's way. I choose to use the Gateron ks-33 low profile as mechanical switch and some modification to the footprint has to be done on Kicad. I removed the led bars and there controllers as you said it won't be used on the final design. That leaves the pin 4 and 5 on the teensy free ( RGB the keys? not sure how that would implement in your code and if I will bother soldering all those tiny ws2812 led ) I was thinking about using the nintendo switch joystick. As it is more compact, no need to have a separate board for it, I think.

Is there anything you would change, add. If you plan to release a new board version soon I will wait but I was thinking that would be a nice device to have for the summer!

[jerry20091103]

Hi Lucas, Removing the LED bars leaves pins 3, 4, and 5 free. I thought about the RGB keys, but ultimately removed them due to increased power consumption and cost. You may add them if you want though. It should not be hard to run the led library within the code.

I actually put Nintendo Switch joysticks in the original design, but I prefer the longer travel of normal joysticks. It's just a personal preference.

I do plan to make a new hardware version. But it won't come maybe until at least late August... (I'm still a busy CS student...) In the new version, most functionality will stay the same. I am hoping to address the issues mentioned in the above posts, and also make it easier to put together too. Currently, some SMT components are really hard to solder. I plan to make it compatible with SMT assembly services like JLCPCB, so people can skip them and just solder the easy through-hole parts. Also, use more common 3.5 jacks, boost converts, and 18650 batteries...

If you still want to build the current version, I would suggest using pin sockets to secure the teensy and audio board, so you can easily reuse them later at the sacrifice of some extra thickness. Also be aware that extra PSRAM chips need to be soldered to the back of teensy, to have longer recording space for the sampler.

[lucas14145]

Hi, Thanks for your answers! I don't really mind SMD components as I plan to make only one copy, I think I could find every component pretty easily on lcsc except the connector you used for SPDIF and I2C if by any chance you have the reference? I hope it's gonna works when I put everything together! 18650 is a great idea if it has enough capacity, do you know the power consumption of the actual keyboard? Good luck with you studies!

[jerry20091103]

Hi, Lucas, The connectors for SPDIF and I2C are generic 2.54mm pin sockets. They are very common, and you don't even need to solder them if you don't use them. I use them to connect stuff on a breadboard. I remember the power draw is 200~500 mA at 5V depending on the screen brightness and volume. Good luck with your build!