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Thread: Progress on a fully custom mouse. Reply to Thread
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  Topic Review (Newest First)
06-16-2020 08:11 AM
gimbas i have yet to test performance, but it should not be a problem, i have the know how, i just don't have the time.

so far it is quite usable, i even game with it, but i am not picky, i'd game with a trackpad if i had to.
06-16-2020 06:56 AM
gipetto there have been many requests for low latency stm32 firmware but nobody with the know how has stepped up as of yet. If you could get 8khz usb reports running I'd say you'll have a few builders.

I was playing around with qmk (qmk.fm/docs) and had keyboard/mouse firmware compiling for the 32u4, however i couldn't get any response from the cursor so I gave up. I used this firmware and changed the matrix scan for the direct pins method. https://gitlab.com/keyboards1/qmk_fi...nuform_r_track I don't have the code anymore but it wasn't a complex change.
06-16-2020 04:10 AM
gimbas Very interesting.

I am currently developing a universal input device firmware, for keyboards and mice, it's not quite ready but it is usable, my daily mouse is running on it. i will sooner or later design my own replacement boards for existing shells, but first the firmware needs to get to a mature state.
Just wanted to leave this here, so that maybe when any of you design new boards you might consider using my firmware.

https://github.com/openinput-fw/openinput

Regards.
05-26-2020 09:16 AM
gipetto > Why did you connect the atmega AREF pin to VCC & not GND (like on Teensy 2.0)?
looks like you found a mistake there.I'll have to correct it. it didn't stop it from working though as capacitors block dc.

>Why are there two resistors (20k & 33k)
the tindie pcb uses a fixed 1.9v regulator. the jlcpcb parts library had no such part available, only 1.8v fixed, so I chose to use an adjustable regulator instead, the two resistors set the voltage. the voltage calculation is given in the rt9179gb datasheet.
i wasn't sure whether to use high value resistors or low value, the datasheet didn't say. but it's stable at 1.93v so it turned out okay. there's also a good bit of spare current in the chip if the resistors draw too much. the 3360 chip runs from 1.8 to 2.1v so using a 1.8v reg could make it unstable if the voltage dipped a little.
if you are using the tindie regulator then use its circuit and vice versa. there are no firmware changes on different regulators.

>would I have to adjust the resistor values
no, wetting current is standardised across most switches. if you use less switches you'll need less resistors, one per pin.
05-26-2020 07:04 AM
dahomosapien Thanks for the replies

So I have decided that I want to make your mouse & use the firmware!
I have noticed a few things after looking at your schematic.

Why did you connect the atmega AREF pin to VCC & not GND (like on Teensy 2.0)?
Why are there two resistors (20k & 33k) connected to the pmw3360 voltage regulator? Is it because you used a Chinese brand alternative? I actually have the same v.reg component used in the tindie 3360 module, so can I just connect it identically to the tindie schematic, or are the resistors & that particular v.reg important regarding your firmware?
If I were to only use just the left & right switches in my version (so no mouse-wheel, middle button, nor side buttons [don't ask why, lol]), would I have to adjust the resistor values or just leave them at 4.7k?

Sorry for so many questions. I just want to make sure I do nothing wrong. Thank you
05-25-2020 05:39 AM
gipetto I didn't make any calculations, I dropped out of school early so don't have a great grasp of circuit design. 22pf seems to be the more common value, perhaps the crystal package on the teensy changes the required load capacitance. some vusb keyboards use a 12mhz crystal so he may have used a different cap size for compatibility with the parts he had on hand.

>those 4.7k resistors
more or less yes. they're actually to increase wetting current to within the specs of the omron switch datasheet. it was an experiment to see if switch life could be extended. there's a conspiracy theory around that says the reason modern mice doubleclick so often is because they use lower switching voltage and less current to blow through the oxide on the switch contacts.
05-24-2020 08:25 PM
TranquilTempest
Quote: Originally Posted by dahomosapien View Post
Thanks for the replies

Regarding the crystal load capacitors - the 2 load capacitors values are 10pf on the Teensy; 20pf on the HSGW Plaid; & 22pf on your mouse. Did you have to make calculations to figure out the correct load capacitance (or am I overthinking)?

Also, what's happening on the left side of the atmega on your schematic, with all of those 4.7k resistors that are also connected to VCC then to the switches? Is that hardware switch debouncing?

Thank you!!
The microcontroller should have a reference implementation in the datasheet or application notes, with the crystal and capacitor values specified.
05-24-2020 06:21 PM
dahomosapien Thanks for the replies

Regarding the crystal load capacitors - the 2 load capacitors values are 10pf on the Teensy; 20pf on the HSGW Plaid; & 22pf on your mouse. Did you have to make calculations to figure out the correct load capacitance (or am I overthinking)?

Also, what's happening on the left side of the atmega on your schematic, with all of those 4.7k resistors that are also connected to VCC then to the switches? Is that hardware switch debouncing?

Thank you!!
05-24-2020 04:08 PM
gipetto If you must know i did it because jlcpcb assembly had a reel change charge for extended components. i forget the exact cost but it was around 3 euro extra. the chinese voltage regulator was also an extended component last time i checked, which was after the plague.
05-24-2020 02:41 PM
qsxcv
Quote: Originally Posted by gipetto View Post
the 49.9Ω & 180Ω resistors added together in parallel give 39.08 ohms, close to the 39ohms of the datasheet. it's often necessary to use multiple components to replace a rare or expensive part.
a 39ohm resistor is neither rare or expensive
but yea if you don't have it on hand, it's indeed annoying to order small quantities from digikey or wherever.


when i replaced 3360 with 3389 in my prototype m1k, i soldered in parallel 2 additional 39ohm resistors to make a 13ohm resistor
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