Electronics
V1 Design files
- Block diagram
- Schematics PDF version
- Layout PDF version
- PCB production files ZIP file
You can find these files in the Files
section of the
Freewatch project.
You can also find them in the Repository (hw/ folder).
This design is Copyright Julian Lewis 2014.
This documentation describes Open Hardware and is licensed under the
CERN OHL v.1.2.
You may redistribute and modify this documentation under the terms of
the
CERN OHL v.1.2.
(https://www.ohwr.org/cernohl). This
documentation is distributed
WITHOUT ANY EXPRESS OR IMPLIED WARRANTY, INCLUDING OF MERCHANTABILITY,
SATISFACTORY QUALITY AND FITNESS FOR A PARTICULAR PURPOSE
Design tools
This electronics design has been made with the KiCad EDA Software
Suite.
KiCad is a Free/Libre Open Source Software Tool which runs on GNU/Linux,
Windows and Apple OS X. It is licensed under the
GPL license.
Component selection
Design notes
GPS passive antenna
GPS RF design guidelines
Low power design
Backlight
Use 0.5 or 1mm plexiglas sheet behind the LCD with four white LEDs.
Here is a cheap plexiglas sheet
supplier:
http://www.plexiglas-shop.com/CH/fr/plexiglas-folie-5m9m5apyxic/plexiglas-folie-blanc-99532-gt-1-0-mm-iqq6a1wurpd~p.html
> Note: After some preliminary tests, it turn out that the plexiglas idea doesn't work well.
Learn more on backlight:
As optical films are hard to get for private customers, using backlight from a broken cellphone display might be an alternative.
Battery life calculation
- http://www.oregonembedded.com/batterycalc.htm
- http://www.csgnetwork.com/batterylifecalc.html
- http://www.ajdesigner.com/phpbatterylife/battery_life_peukert_number_time.php\#ajscroll
Bootloader
To enter the bootloader, DBG_SWCLK (PF0) must be pulled high and the
EFM32 must be reset.
See application note
AN0042
> Note: We should find a way to run the bootloader from the main application (without having to open the case!).
The original bootloader has been modified to allow entering it from the application (reset menu + watch button pressed).
Power profiling
Foresee sensors, test points on the PCB in next revision?