Mayavi

Description

I've been neck deep in consulting projects, missing the days where I could fool around with my personal projects. When my daughter asked me to make a watch for her as a birthday gift recently, it seemed like the perfect opportunity to get back to some tinkering. I hope I can finish this project on time, and hope to record my progress here.

This is an Open Source Hardware Project, and you can find the files here:

https://github.com/electronut/ElectronutLabs-mayavi

Details

Specifications

Nordic nRF52832 Raytac MDBT42v module
0.96" OLED display breakout
ST Micro LIS2D12 accelerometer
2 x Side mounted buttons
40 mAh LiPo battery
Buzzer SMD 5 mm x 5 mm

PCB Design

This is a two-PCB design, with the 0.96 inch OLED PCB soldered on to the botton PCB which has all the components, including the LiPo battery (glued) on to it. That leaves the bottom surface of the PCB free and flat for wearing.

Project Logs

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Started on PCB...
Mahesh Venkitachalam • 07/07/2018 at 05:01 • 0 comments
etch a sketch
Mahesh Venkitachalam • 07/05/2018 at 09:17 • 0 comments

Watch will feature an "etch a sketch " mode...
Can set time over BLE now...
Mahesh Venkitachalam • 07/02/2018 at 09:03 • 0 comments

With Nordic UART Service and a simple text command, can now set time...
Etch A Sketch
Mahesh Venkitachalam • 06/21/2018 at 11:19 • 0 comments

Since we have two buttons, I think Mayavi will have a drawing mode - like an Etch A Sketch. Double taps can clear the screen thanks to accelerometer...
Schematic...
Mahesh Venkitachalam • 06/14/2018 at 12:09 • 0 comments

Almost done with schematic...
No module, switching to SoC
Mahesh Venkitachalam • 06/11/2018 at 06:02 • 0 comments

This will do, and I can skip the 32 kHz Xtal...
State Diagram...
Mahesh Venkitachalam • 06/11/2018 at 00:52 • 0 comments

This should help me with coding. Made with draw.io...
Accelerometer Driver, buttons...
Mahesh Venkitachalam • 06/10/2018 at 05:22 • 0 comments

Moved to nRF5 15.0 SDK. Added LIS2DH12 accelerometer driver and GPIOTE support for button presses. Code pushed...
Prototyping with the nRF52-DK...
Mahesh Venkitachalam • 06/09/2018 at 07:02 • 0 comments

Started prototyping the project with nRF52-DK. I had previously ported the Adaruit GFX and SSD1306 libraries to nRF52, so getting a counter up and running wasn't too hard...
To a man with a hammer...
Mahesh Venkitachalam • 06/08/2018 at 07:46 • 0 comments

...everything looks like a nail.

I put some thought into what controller I should use for the watch, and what it should display.

My initial idea was to use an AtTiny chip. Then, I though that an AVR might give me a bit more flexibility, Arduino bootloader, etc. Well, then why not an ARM? SAMD21 will do nicely. Finally I thought - I'll just use an nRF52832 - ARM Cortex M4, gives me BLE to fool around with, and that's the platform I am most familiar with anyway.

Also, after thinking about LEDs, bubble displays and tiny 7-segment displays, I decided on an OLED since that gives the possibility for some fun graphics.