Capacitive Touch Keyboard Business Card

Description

The project aims to combine a business card with a functional USB-C capacitive touch keyboard on a PCB. The initial idea focused on using microcontrollers like the RP2040, Atmega32u, and STM32F103, but these lacked native capacitive touch functionality. After further research, the CH32V303 was selected due to its built-in USB 2.0 and 16 capacitive touch channels, capable of supporting up to 48 keys through multiplexing. However, to reduce costs, the project later switched to the CH582 (CH582M), which also has capacitive touch capabilities, USB support, and even includes Bluetooth functionality, potentially allowing wireless communication.

The goal is to keep the design as affordable as possible while ensuring it remains a unique, functional business card. The final device would serve as a 40% keyboard and be a demonstration of both electronic engineering skills and the practical use of capacitive touch technology.

Components

1 × CH582M Microcontroller

1 × ME6211C Voltage Regulator

1 × 32MHz Crystal

1 × 10uH Inductor 0806

1 × Some SMD resistors & capacitors

Project Logs

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Costs
Ricardo Daniel de Paula • 10/07/2024 at 18:56 • 1 comment
- CH582M - 0.87$ USD
- SMD Inductor 0806 - 0.22$ USD
- 32MHz Crystal - 0.22$ USD
- LDO - 0.09$ USD
- capacitors and resistors - 0.10$ USD
TOTAL: 1.50$ USD in Components
Finishing touches, Wireless and more.
Ricardo Daniel de Paula • 09/26/2024 at 22:02 • 3 comments

Here's the finished schematic. I added a programming header and a wireless antenna.Here's a close look at the antenna and main electronics:

And here's (probably) the finished result::
Changing to CH582M
Ricardo Daniel de Paula • 09/18/2024 at 21:52 • 0 comments

Well, last week after a lot of time spend in research i decide to use the CH32V303 microcontroller from the chinese manufacture WCH, mostly because it's price. but after read after read the documentation and start some PCB routing i discovered that CH32V303 has 4 versions [1}, 3 with 16 TouchKey pins and only one with 10:

And for the surprise of no one the version that i initially choose for this project was the one with only 10 touch capable pins, util there everything was "ok" i only had to pick the version with more pins... but checking the price it turns out the CH32V303RBT6 is at least 50% more expansive than CH32V303CBT6 in quantity:

I really wanna this project been cheaper as possible. So i had no other option than start to search for microcontrollers again. So i spend some hours looking for Silver.. than a i found Gold; The CH582M:

The chip not only have 14 touchKeys and USB support, but also have Bluetooth Low Energy module AND are in the same price of the CH32V303, so it is the perfect choice, and maybe it can add a feature that wasn't in my plans; wireless.

Here's the actual drawing:
A dream
Ricardo Daniel de Paula • 09/12/2024 at 20:54 • 0 comments

For now all i have is the ideia, a dream and some initial draws.

I initially started to thinking which microcontroller i will use for this project, and some easy ideias come to my mind, like the; RP2040, Atmega32u and STM32F103, all with USB interface Build-in and a vast community examples of how to use them like a keyboard, but after some research i found none of them has capacitive touch functionality, which is not exactly a problem, cause this functionality can be easily implemented by software, but with little bit of more research i discover the CH32V303, which accordingly to his datasheet have built-in USB2.0 and 16 channels of capacitive touch; with this i could multiplexing 12x4 touch pins and get a 48 keys, which is more than enough to consider this a 40% keyboard. The chip is very cheap (:D) and just need a few passive components to work well. So the CH32V303 was the first choice for this project, i hope the software development doesn't make me regret.

Other thing that i wanna for this project is a PCB usb-c connector where i get the ideia from here, this make the project cheaper and more easy to give away it to someone else, which is the propose of a business card, but i will talk more about costs later.

Here's the first drawings: