Making a DIY GPS to replace the Edge 810

The GPS main tasks would be:

• Show ride ral time info (bike computer) like speed, cadence, temperature, grade, ascet/descent, altitude, HR, power
• Save all info to internal flash every X seconds
• Sync with strava, endomondo, ridewithgps, garmin connect etc

Hardware requirements:

• e-paper LCD (B&W) to have the best under sunlight experience (no touchscreen)
• Variable intensity backlight
• 4 buttons (3 on one side + 1 on the other)
• Speaker

• GPS + GLONASS + Galileo receiver
• Precision temperature sensor +/-0.5 Celsius or better
• Barometer
• Accelerometer
• Giroscope
• Ambient light sensor
• Fuel gauge for accurate battery measurement
• 8 channel ANT+ tranceiver
• BTLE tranceiver

• Microusb connector
• 500mA limited usb charging
• LION battery managemente ic onboard
• Battery large enough to allow 24h operation

• ARM MCU
• Real time clock (RTC) updated via GPS and/or NTP
• Hardware Watchdog
• USB 2.0 
• Internal flash large enough to save 48h of ride data every 1/2 second
• RAM memory (for TBT nav handling)
• microSD reader
• Unique hardware serial number

• IPX7 water resistance (up to 1m/30minutes immersion)
• Garmin compatible bike mount
• Smaller than Garmin Edge 810 (5.2 x 9.3 x 2.5 mm)
• Lighter than Garmin Edge 810 (98g)

GPS software requirements:

• ANT+ sensors support
• BTLE sensors support
• Transparent realtime translation ANT <-> BTLE (to allow using the mobile phone with ANT sensors)
• Compressed propietary internal flash saving
• Dumping data to pc is done as XML files (realtime conversion)
• Date, hour, temperature, latitude, longitude, altitude, HR, power, cadence, speed, g-forces saved
• Saving frequency user defined 0.5s -> 1minute
• "Smart" saving frequency mode where data is saved only if a significant change is detected in one of the sensors
• Manual backlight with user defined timeout + auto mode based on ambient light
• Day/night display mode user defined or automatically changed based on ambient light
• User selection. The unit allows for 3 users, each of one with its own "partition" and web sync accounts
• Bike selection (up to 10 bikes)
• Automatic bike selector. If activity is detected in a sensor thats unique to a given bike then bike profile is changed automatically
• Automatic wheel size calculation from gps data
• Dynamic switching between gps data and wheel rotation sensor based on best detected conditions
• Ascent/descent grade calculation done by distance/altitude averaging + gyro data for improved accuracy
• auto pause, auto start, auto stop, power off automático
• Watering alert
• Ranges alerts (speed, cadence,HR,power)
• Movement detected while not saving alert
• Low phone batt alert
• If gps has low batt then everything is disabled but ANT/BT sensors and saving to maximize the recorded data
• CLI shown upon receiving a call. A button is provided to reject the call and another one to reject the call and send a predefined text message to the caller 
• TBT navigation without map showing...just arrows n intersections
• Livetrack . updates every 30 secs
• Livetrack init/reinit/stop from the gps function

PC software requeriments:

• Windows/osx/linux versions 
• Create/Edit/delete gps screens and all the data shown in them
• Create/edit/delete users and related data (age/weight/size/gender)
• Edit general gps settings like saving rate, backlight, alerts etc
• BT phone pairing
• WEB sync accounts configuration (Strava ridewithgps etc)
• Create/Edit/delete bike profiles
• Activity saving in GPX/FIT/TCX formats
• Automatic sync with web sites
• GPS data backup/restore
• WEB site data backup

Mobile app requeriments:

• IOS and Android
• livetrack
• dataplan costs using user provided rates
• Auto sync activity upon finishing
• Mobile dataplan sync usage enable/disable flag
• Activity summary view (distance/time etc) ... no maps no graphs as we have the more comfortable pc to do it