Delivery Day
Alright, brain parts came in, and I began messing around and getting familiar with components this week. Pictured below you see the:
Arduino
BT chip
Ultrasonic distance sensor
Gyroscope + Accelerometer
Speaker
MicroSD board
16p port expander
Buttons and LEDs
Wireless charging components (a late additon)
The first thing I wanted to get a handle on was estimating the distance between two Bluetooth devices, as the entirety of the system relies on it pretty heavily. A number of parameters are involved when calculating the distance between two devices, including Received Signal Strength Indicator (RSSI), Measured Power (a value that indicates the expected RSSI value from 1-meter, calibrated by the factory), and an environmental constant.
Attached a screenshot below. I've got some simple code that scans for nearby BT devices, grabs the RSSI, and calculates the estimated distance. This is the output for the BT chip tracking my headphones. I'm now running into some of the issues described in the article above, the unstable signal strength just results in inconsistent distance values, and I'm not sure dropping outliers would help. The ESP32 board also includes Wi-Fi functionality, so I'll look into estimating distance using that as well, but it's beginning to look like we may need a GPS chip to get the location accuracy down to ~a foot. (Ha, I’ve since learned US Congress has some aversions to this.)
Regardless, getting the chip to begin broadcasting over Bluetooth and estimate distance between itself and other devices is a huge development milestone for the project. In the next chapter we’ll get a rough draft of a mobile app so that we can estimate distance between two specific devices. Thanks as always for reading if you’ve made it this far!
