How to connect a logic level shifter/voltage regulator to the Seeed XIAO RP2040 - Page 1
Forum section: electronics / projects

author: ziomario
author_rank: Contributor
timestamp: June 25, 2025, 05:42:17 pm
content: Hello to everyone.I'm trying to create a cyberdeck based on FreeBSD. I'm not sure what the final form is. I would like it to be something like this,more or less :https://ibb.co/99J6VrWvThe approach that I want to take is to use as many USB and HDMI peripherals as I can,so : a) HDMI screen is easily interchangeable. b) USB keyboard and touchpad (circle glidepoint touchpad :https://www.cirque.com/glidepoint-circle-trackpads)c) portable batteryNow. What I want to do now is to convert the circle glidepoint touchpad into one USB device that can be recognized by any operating system,such as FreeBSD. Yes,because natively it is an I2C device.I'm reading this guide to understand how to implement that layout.https://beekeeb.com/cirque-trackpad-i2c-on-corne-keyboard/At some point,he told :5VIf you can power it with 2.5-3.6V, you can skip this section. The type-c breakout board runs at 5V. So we cannot directly power it directly. We can probably use a logic level shifter and voltage regulator to provide 3.3V. Alternatively, according to the post on Cirque Forum, the trackpad can run at 5V when R7 and R8 are removed.Let's start saying that I won't remove any resistors,but I want to "a logic level shifter and voltage regulator to provide 3.3V"With the help of some users of the various forums where usually I ask questions,I ended up creating this layout :QuoteConnection Cable / Board NotesQuoteWhat I don't understand is how to connect the TXB0108 or the TCA9517 to the Seeed XIAO RP2040. I need to see it clearly and physically under my eyes. It's not enough for me to guess or try to understand it by reading some good sentences. Unfortunately I'm still a beginner.I don't understand when the voltage regulator is needed and when it is not. For sure I don't want to shut it down or turn it up manually. My will is to keep attached and let it decide when it should be turned on or not.Can the TXB0108 or the TCA9517 decide automatically when it is needed or not to run ? Can you suggest a regulator that decides by itself when it is needed or not ?

author: ziomario
author_rank: Contributor
timestamp: June 27, 2025, 01:39:31 pm
content: Maybe I found something that could work :https://www.amazon.in/Step-down-Converter-DC8-2-32V-Transformer-Regulator/dp/B0CFHXWJH4If it is useful,in Which link of the chain would it go into ?

author: Paradroid
author_rank: Contributor
timestamp: June 30, 2025, 03:10:16 pm
content: I don't see where you need voltage translation. THe track pad is a 3.3V device, and the RP2040 is also 3.3V, so you can connect them without any level shifting. Further, the RP2040 gets it's power from the USB host - it has it's own 3.3V converter for power, and if you're lucky, there's some juice left to supply the track pad.Jens

author: ziomario
author_rank: Contributor
timestamp: July 01, 2025, 10:57:54 am
content: This board works :https://fingerpunch.xyz/product/svlinkyjust because I can attach the 12-pin FFC connector directly to the board. It's good if the circle touchpad is 23mm. But for my FreeBSD cyberdesk I want to use the smaller version of their touchpads,at 16 mm. Now it comes the problem. The svlinky board does not accept a 6-pin FFC connector. So it should be recreated from scratch. Since it is open source,it can be done by some good engineer. What I want to know is how much money can cost to me to hire someone for this job.

author: abeyer
author_rank: Frequent Contributor
timestamp: July 03, 2025, 06:57:35 am
content: Quote from: ziomario on July 01, 2025, 10:57:54 am$300 USD

author: ziomario
author_rank: Contributor
timestamp: July 03, 2025, 07:36:01 am
content: Thanks bro.Even the firmware should be rewritten ?

author: abeyer
author_rank: Frequent Contributor
timestamp: July 03, 2025, 07:43:12 pm
content: Maybe don't thank me too much... the reason I just threw out some number without any context was kind of a comment on your request: I don't think there's enough context to give a good answer.Quote from: ziomario on July 03, 2025, 07:36:01 amI dunno, you're the one who said that board would work but just had the wrong connector. If that's the case, why would you rewrite the firmware?

author: ziomario
author_rank: Contributor
timestamp: July 03, 2025, 08:09:05 pm
content: There is context. Just give a look at the project of svlinky :https://github.com/sadekbaroudi/svlinkythere is everything. How to build it and how to make it work. What do you need more than this ?---> I dunno, you're the one who said that board would work but just had the wrong connector.nope. I didn't say it, but its creator. I only reported what he said.--> If that's the case, why would you rewrite the firmware ?I asked because I don't know. And I know I don't know (Socrates).

author: abeyer
author_rank: Frequent Contributor
timestamp: July 03, 2025, 09:13:42 pm
content: Quote from: ziomario on July 03, 2025, 08:09:05 pmSure, if you don't know and expect someone to go figure it out, that's fine, but you need to be clear about that (it wasn't originally, at least to me) and you'll be paying for the research, too, as you're not asking someone to just tweak an existing board design, you're asking them to figure out the solution.

author: ziomario
author_rank: Contributor
timestamp: July 03, 2025, 10:21:23 pm
content: ----> Sure, if you don't know and expect someone to go figure it out, that's fine, but you need to be clear about that (it wasn't originally, at least to me) and you'll be paying for the research, too, as you're not asking someone to just tweak an existing board design, you're asking them to figure out the solution.ok. Do you want increase the cost ? from 300 to ?

author: abeyer
author_rank: Frequent Contributor
timestamp: July 04, 2025, 07:15:04 pm
content: Quote from: ziomario on July 03, 2025, 10:21:23 pmTo be clear I wasn't offering that price myself, just threw it out there as a wild guess of what you might be able to find someone to take for adjusting the pcb design that you linked before. I'm actually slightly interested in their little touchpads and controllers now, and might have been tempted to actually make an offer just as an excuse to get and play with them, but when I took a look it's not even clear if those 16mm ones are easily available to purchase, so wouldn't even consider it without knowing what it would take to source parts. The places I see offering the Cirque hardware only seem to stock the larger sizes and the devkit.If you're serious about paying someone to do this, I wouldn't worry too much about the budget up front... offer something and see if you get takers, if not you can always offer more. Especially on the freelancer sites that tend to attract lots of bids from LCOL places, I suspect that $300 figure is at least a reasonable place to start. One thing I would suggest, though, is just write out your requirements and specificationsonlyand don't go off suggesting half-way solutions and open source projects that might be modified. In my experience doing consulting work, a client that came to me with half of a solution that they wanted me to fix was almost always more work and more hassle than one that had a good requirements specification alone.Also, not sure how attached you are to the Cirque touchpad... but if you're open to other solutions with a small touchpad: Have you looked at the Blackberry Q20 keyboard assemblies? They have both a keyboard and tiny touchpad pointing device in one unit, seem to have a number of suppliers still offering them, and there is an open source board design already for a usb interface to it.

author: ziomario
author_rank: Contributor
timestamp: July 04, 2025, 08:36:58 pm
content: ---> They have both a keyboard and tiny touchpad pointing device in one unit, seem to have a number of suppliers still offering them, and there is an open source board design already for a usb interface to it.I like the Blackberry Q20 keyboard,but I haven't found any supplier that ship it for a reasonable price. Can u suggest one ? It is always out of stock.I asked to a pcb company to build one of that from scratch,but I saw that the price is higher that the solution that I've found at the moment (it's about using the cardKB + the circle touchpad + the svlinky).

author: abeyer
author_rank: Frequent Contributor
timestamp: July 04, 2025, 09:21:21 pm
content: Not sure where you're at for shipping/availability, but right now the first two listings I see on ebay in USA are about $20-$30 USD each delivered.Honestly, though, if you aren't looking for large quantities, it might even make sense to just buy up cheap blackberries and pull the keyboards... they're obsolete and dirt cheap, I've seen the whole device sold for similar prices.

author: ziomario
author_rank: Contributor
timestamp: July 04, 2025, 09:31:41 pm
content: I want to be sure that you are talking about this :https://lectronz.com/products/blackberry-bbq20-bleusb-keyboard

author: abeyer
author_rank: Frequent Contributor
timestamp: July 04, 2025, 10:08:25 pm
content: Quote from: ziomario on July 04, 2025, 09:31:41 pmThat's one of them using that same keyboard module, yeah. Being open source there have been a number of similar variants/designs. I don't know of anyone actively selling assembled products right now (though it looks like that one plans to soon), but the bare keyboard modules are available to build your own.

author: ziomario
author_rank: Contributor
timestamp: July 04, 2025, 10:16:00 pm
content: ---> but the bare keyboard modules are available to build your own.unfortunately not. The bare keyboard will not work as is. It needs to be connected to a special cable,to a board that should be created from scratch. This costs money and it needs competences that I don't have. Only the preassembled product can be interesting.

author: abeyer
author_rank: Frequent Contributor
timestamp: July 04, 2025, 11:10:46 pm
content: Quote from: ziomario on July 04, 2025, 10:16:00 pmSo if I've got the score board correct, looks like:cirqueq20needs a special cable:✅✅needs a board created:✅ (don't know if the existing one would work, and needs changes for connector)✅ (known good design ready to build)needs money/skills:✅✅includes keyboard:❌✅

author: ziomario
author_rank: Contributor
timestamp: July 04, 2025, 11:45:53 pm
content: What is this ? Your scheme is wrong.The FPC 12 pin cable used by the circle touchpad 23mm works out of the box with the svlinky controller because is VIK compatible.This is the costs scheme :a) circle touchpad 23mm = 10 EURb) svlinky = 20 EURc) FPC 12 pin cable = 2 EURd) shipping costs = 20 EURTotal = 50 EURBB Q20 USB Keyboard created from scratch by a PCB company = 150 EUR. Already asked a quote from 2 different PCB companies.

author: abeyer
author_rank: Frequent Contributor
timestamp: July 05, 2025, 12:26:45 am
content: Maybe I'm confused, but I thought you said you needed the 6 pin connector, didn't know of a board that had it, and didn't know if the firmware supported it?

author: ziomario
author_rank: Contributor
timestamp: July 05, 2025, 12:41:31 am
content: --> didn't know of a board that had it, and didn't know if the firmware supported it ?exactly. Too many unknowns. That option is excluded ; it does not make sense to put in the equation an excluded option. And also the option to ask to a pcb company to create the BB Q20 USB keyboard is excluded because the high costs,ANYWAY,this option is more interesting than the previous one,so it worths to talk about it a little bit. I found interesting compare it with the option that I have chosen.PS :The costs scheme previously showed is wrong. This is the correct one :a) circle touchpad 23mm = 10 EURb) svlinky = 20 EURc) FPC 12 pin cable = 2 EURd) cardKB = 20 EURd) shipping costs = 20 EURTotal = 70 EUR