After much negative experience with Android GPS tracking (battery usage, bad reception) I decided to build my own dedicated GPS tracker despite the fact that multiple similar devices are readily available on the market.
- Quectel L70B GPS receiver module with low power tracking function. They claim 1.4mA tracking current draw under static conditions. We will see.
- STM32F401 microcontroller in a QFN48 package, low power run mode
- EA DOGS 102x64px graphic LCD module with low power consumption (0.25mA)
- USB connections for charging and downloading data
- SPI serial flash for data storage (8Mbit/16Mbt)
- 600mAh 3.7V LiPo cell
The goal is 5mA current draw which should be enough to provide nearly 4 days of continuous logging using the mentioned 600mAh LiPo cell. Such cells are available in local stores or on eBay.
The following items will be saved:
- 32 bits for the actual time
- 32 bits for latitude
- 32 bits for longitude
- 16 bits for height
- 16 bits reserved for header and other data
Which gives 16 bytes for a single point or 65536 points in a 1MB flash memory. Considering 5 second logging interval (should be enough fir hiking), the flash memory should suffice for 91 hours of logging, which is nearly 4 days.
As of 2016-02-06, basic requirements are determined and the schematic is ready. Board layout is WIP.
TODO
TODO
You can access the schematic/layout files and firmware at https://github.com/iqyx/lcd-gps-tracker