Capacitive Touch Screen

Project Summary

A friend of mine is working on developing a device that can display any MTG card and perform several touch screen operations to interact with the card in various ways. He asked to me help with the hardware design. Below is a summary of the project concept along with work to date. This project covers concent from several weeks and will continue to evolve.

Concept

Are you tired of not having the exact obscure token you need to obliterate your feeble opponents! Well look no further. I present.... The Shapeshifter! I built this card sized (it is slightly taller than a magic card by about 2cm) token finder to search up any token that Wizards of the Coast has ever printed!

The post below shows an early protype using this dev board

Here is a prototype demo made for the internet community to assess interest link This inital Redit post recieve over 1.2K likes and more than 90 comments.

Design

The objective of the hardware design is to turn the basic prototype shown above into a fully functional stand allone device. Major changes from the inital prototype include:

1. Designing a board that contains only the required components and functionality (unlike the dec board shown above)

2. Add a battery and charging system including:

   a. Functionality to charge while the device is in use

   b. Voltage reulation so the device functions normally regardless of battery level.

   c. Additon of an on/off switch

3. Select and integrate a slightly larger screen that can be easily seen at fairly extreem viewing angles

Based on these requirements I created the simple schematic sketch shown below. This helped me to identify the components I would need and start to narrow the part selections.

BOM

Part selection required a lot of background research. ChatGPT was a useful resource to help me understand the subtle differences between different components and part numbers. Eventually I settled on the following parts and place an order for the parts that our lab does not have on hand. There are several components (such as the USBC port) that I will need to use a breakout board for the first version the prototype because the final componenets are too small to work with given the tools we have available.

Status	Component	Part Number	Description	Notes	Links	Price (€)
On Order	DLS30035B1 Display	DLS30035B1	3.5” IPS TFT SPI	SPI bus, same touch controller family	Datasheet
On Order	DLS31040B1 Display	DLS31040B1	4.0” IPS TFT SPI		Datasheet
Have	ESP32 Module	ESP32-S3-WROOM-1-N16R8	MCU		Specs · Buy	5.62
Have	USB-C Connector	USB4085-GF-A	USB-C (USB 2.0)	Too small → use breakout for testing	Datasheet · Buy	0.76
Have	CC Resistors	5.1kΩ 1%	USB-C config resistors		Specs · Buy	0.01
Have	USB ESD Protection	TPD2EUSB30	USB ESD diode	One per required voltage line	Datasheet · Buy	0.70
Need	Charger + Power Path	BQ24074RGTR	LiPo charger + power mgmt		Datasheet · Buy	2.14
Need	Buck-Boost Regulator	TPS63070RNMR	3.3V regulator	Stable voltage as battery drops	Datasheet · Buy	2.57
Have	microSD Socket	DM3AT-SF-PEJM5	microSD push-push		Datasheet · Buy	2.23
Have	Li-Ion Battery	1S 3.7V 2000–3000mAh	Rechargeable battery	Verify compatibility with components	Specs · Buy	2.10
Need	Slide Switch (SPDT)	JS102011SAQN	Surface-mount switch		Datasheet · Buy	0.67
Total						16.80

Preliminary Schematic design

In order to create the first version of a custom board I needed to first find all of the required components. Some of the components were not available in the KiCAD library that I had already downloaded.

Adding additional components to KiCAD library I used SnapEDA to find scematic sketchs and footprints for the outstanding compenents. After creating an account this site let me download the component and add it to my KiCAD library following instructions listed here

Once I had all the required components I started tagging the pins and adding supporting componets such as resistors and capacitors.

Current version of schematic Check regarding IP before adding

To Do and Next Steps

Task	Person	#	Subtask	Status
Get prototype of board	Yara
Hardware verification prototype		1	Schematic sketch	Done
		2	Build initial BOM	Done
		3	Confirm JLCPCB	In Progress
		4	Order parts	Done
		5	CAD schematic	In Progress
		6	Board design
		7	Mill board
		8	Solder components
		9	Testing, troubleshooting
		10	Repeat 3–8 as needed
Manufacturer Prototype		11	Update schematics after initial test
		12	Generate finalized BOM
		13	Create manufacturing design
		14	Place order
		15	Test and verify
		16	Repeat
Test and select new screen