How to Build a SmartWatch?

Wearable technologies are becoming more and more ubiquitous in our daily life. This tutorial presents how to build a smartwatch. It involves electronics to program a liquid crystal display and 3-D printing to make the watch case. This project is a hands-on introduction to wearable technologies conception.

BioWatch/smartwatch at main · VivienP/BioWatch

Contribute to VivienP/BioWatch development by creating an account on GitHub.

github.com

BioWatch/smartwatch at main · VivienP/BioWatch

Context

The first liquid crystal display (LCD) was built in 1967 by Lechner B. et al. [1]. The LCD technology allows designing low-power flat panel displays [2]. The first LCD screen watch was created in 1968 by Zanoniet al. [3]. Moore G., the co-founder of Intel Corporation, has highly contributed to developing this technology [4]. LCDs are now used in most screens, including smartwatch (SW) displays.

The Pulsar NL C01 was designed in 1982. This device, known as the first SW, is a user-programmable watch [5]. Since then, the number of SW features has increased sharply. SWs features have been multiplied with recent technological progress. SWs have a broad application scope, including connectivity, sports, and health areas [6]. The great personalization of these devices has thus boosted their popularity [7]. Intelligent wearables' shipment volume stood at 270 million units in 2020. It is projected to reach 770 million units by 2026 [8].

Technological tools are becoming more and more accessible to individuals. Electronic objects are easily programmable thanks to prototyping platforms. 3-D printing technology allows the creation of tailor-made objects. This accessibility now allows non-professionals to create complex devices such as a smartwatch.

Skills & Opportunities

The first skill learned through the tutorial is programming LCD screens. Programming such devices allow printing images, videos, GIFs, and various data. The second skill is slicing 3-D modelized objects. It is a preliminary step to use a 3-D printer. Knowing how to slice a piece allows printing any 3-D object like a watch case. Building this smartwatch is a first approach to wearable technologies.

Requirements

This project involves several prerequisites.

A 3-D printer and its printing software associated,
A 1.28" round LCD display module from WaveShare (orderable here)
An electronic board compatible with the LCD screen,
A wristband from an old watch,
8 Electronic wires,
A USB key,
4 small screws of 2 millimeters diameter (optional).

Tutorial

This project is divided into three steps:

1. LCD programming

2. Case 3-D printing

3. Smartwatch assembly.

1. LCD programming

1.28" round LCD module from WaveShare is a module with an embedded GC9A01 driver . The module supports Raspberry Pi, Arduino, and STM32 controller boards. It uses Serial Peripheral Interface bus (SPI). A bus is a means for transmitting data between several digital system components. SPI is a synchronous serial communication interface specification. Short-distance communication involves SPI, primarily in embedded systems. The GC9A01 driver datasheet is available here.

1.1. Hardware Connexion

• Realize the hardware connection depending on electronic board:

LCD	GC9A01	Arduino	STM32	Raspberry Pi	Raspberry Pi
PIN	Description	UNO	STM32	BCM2835	Board
VCC	3.3V/5V Power input	5V/3.3V	3.3V/5V	3.3V	3.3V
GND	Ground	GND	GND	GND	GND
DIN	SPI data input	D11	PA7	MOSI	19
CLK	SPI clock input	D13	PA5	SCLK	23
CS	Chip selection, low active	D10	PB6	CE0	24
DC	Data/Command control	D7	PA8	25	22
RST	Reset	D8	PA9	27	13
BL	Backlight	D9	PC7	18	12

1.2. Software configuration

Install the GFX librairy. For Arduino, download the ZIP folder from github. Click on the green button called "Code". Then click on "Download ZIP". Open the Arduino IDE. Click on "Sketch" in the menu, select "Include Library", and "Add .ZIP Library...". Select the ZIP folder downloaded before.

💡

A library is a set of functions that simplify the programming of specific devices. #include Libraryname.h allows to use a library. GFX is a full-featured library for standard IoT drawing.

Load the clock example from the library. For this, open Arduino IDE. Select "File", "Examples", "GFX Library for Arduino" and click on "Clock".

💡

Examples are pre-written codes coming with the library. The clock example prints a watch dial on the screen.

Print line numbers. For this, click on "File", and "Preferences". On the setting tab, select "Display class numbers".

💡

Line numbers help identify the lines to be modified in the following steps. They are not necessary for the proper operation of the code.

• Recover the data bus class below. Copy and past it below line 30. Comment line 30 by writing "/* " at the line beginning. /* cancels the line of code.

Arduino_DataBus *bus = new Arduino_SWSPI(7 /* DC */, 10 /* CS */, 13 /* SCK */, 11 /* MOSI */, -1 /* MISO */);

💡

A data bus is a computer subsystem. It allows data transfer between two electronic components. It must be defined for the communication between the board and the GC9A01 driver.

Recover the display class below. Copy and past it below line 33. Comment the line 33.

Arduino_GFX *gfx = new Arduino_GC9A01(bus, 7 /* RST */, 0 /* rotation */, true /* IPS */);

💡

A display class defined the features of a display (Size, Colors, resolution...). GFX library supports several display classes. GC9A01 LCD is one of them.

Upload the code.

💡

The screen is supposed to print a watch dial. If not, change the voltage supply from 3.3V to 5V. Upload the code again.

2. Case 3-D printing

Download the STL file.

💡

An STL file format (for STereo-Lithography) describes the surface geometry of a 3-dimensional object. It is used for rapid prototyping and computer-aided manufacturing. The STL file has been realized from a 3-D modelization of the watch case.

Upload the STL file in 3-D slicer software.

💡

A slicer software allows slicing a 3-D modelization file in several slices.

Define the layer height equal to or below 0.10 millimeters.

💡

The thinner the layer thickness, the higher the piece's quality. The lighter the layers, the longer the print time.

Define the filament type used and the printer used.

Here polylactic acid plastic and Original Prusa MINI.

Choose supports everywhere.

💡

Supports are necessary depending on the piece's geometry. They allow maintaining certain parts of the piece during printing.

Slice the piece.

💡

The slicer software creates one slice for each layer.

Generate the G-code.

💡

G-code is a programming language. It is used for Computer Numerical Control (CNC). A g-code program defines the movements that a CNC machine will perform.

Download the g-code on a flash drive.

💡

Some printers read USB keys, others SD cards.

Plug the USB stick into the printer and print the case

💡

Navigate in the printer human-machine interface to find the piece. Refer to a 3-D printing tutorial if necessary.

Remove the supports cautiously from the piece.

3. Smartwatch assembly

Insert the LCD screen inside the enclosure.
Plug the electronic cables into the LCD screen.

💡

Push the connector with a screwdriver if necessary.

Four screws of 2 millimeters diameters can be used to fix the case and the screen together.
Recover the wristbands from an old watch. Recover the two small iron rods as well.

💡

A thin blade can be used to fold down the ends of the rods.

Insert a rod on the case holes provided for this purpose.

Reproducibility

An evaluation has been led to evaluate the reproducibility of this tutorial . A group of 5 people has realized this tutorial. They all used an Arduino Uno and the Arduino IDE to program the driver. They all resort to a Prusa Mini 3-D printer and the PrusaSlicer software to print the case. Four individuals were familiar with electronics, and three were familiar with 3-D printing.

They all achieved this tutorial. The five people individually judge the difficulty of the tutorial steps (straightforward, minor difficulties, major difficulties but still enjoyable, major difficulties and not enjoyable, not succeeded). On average, they realized the LCD screen programming part with minor difficulties. On average, they found the case 3-D printing and the smartwatch assembly parts straightforward.

Participants unanimously found the didactic content educational. They all feel like their electronic or 3D slicing skills have increased. One person wants to make another tutorial on DIY wearable technologies.

Conclusion

This tutorial proposes to make a first smartwatch from scratch as easily as possible. It makes the design of a smartwatch widely accessible. This DIY project is a first experience of wearable technologies for beginners and confirmed makers. However, it has some limitations. First, the watch is not on time. Secondly, the device is not wearable. The Open Smartwatch Project overcomes these limitations. It consists of hardware modules (including the GC9A01), 3-D printable cases, and a custom operating system. It requires good knowledge of electronics and programming.

References

Lechner B., Marlowe F., Nester E. & Tults J., "Liquid crystal matrix displays", In: IEEE International Solid-State Circuits Conference, 1969, pp. 52-53, doi: 10.1109/ISSCC.1969.1154684
Cristaldi D., Pennisi S., Pulvirenti F., Liquid Crystal Display Drivers: Techniques and Circuits, 2009
Castellano J., The History of LCD Development, 2005
Sethi A.K., “Chips” and Displays. In: The Business of Electronics. In: Palgrave Macmillan, 2013, doi: 10.1057/9781137323385_9
Dehghani M., Exploring the motivational factors on continuous usage intention of smartwatches among actual users, Behaviour & Information Technology, 2018, 145-158, doi: 10.1080/0144929X.2018.1424246
Romanski, B., Sherman, D.E., Rosenthal, J., Alassaf, D., Nayame, J., & Daim, T.U., Roadmapping Future: Technologies, Products and Services, 2021, Technology Roadmap: Smartwatches, pp209-223, doi: 10.1007/978-3-030-50502-8
Chen X., Chen W., Liu K., Chen C., & Li L., A comparative study of smartphone and smartwatch apps, In: Proceedings of the 36th Annual ACM Symposium on Applied Computing, Association for Computing Machinery, 2021, 1484-1493, doi: 10.1145/3412841.3442023
Mordor Intelligence, Smart Wearable Market - Growth, Trends, Covid-19 Impact, and Forecasts (2022 - 2027), 2021