This project is focused on being a discrete addition to your glasses arm, providing a subtle haptic “nudge” toward Magnetic North based on where you are gazing.

While optimized for eyewear, the “Corvid Compass” is a versatile charm. It can be tucked behind the ear, hidden under a beard, or even worn as a pendant * Though as a pendant or cuff/pocket clip, it only shows North relative to your chest's orientation.

Wherever it sits, it gives you that migratory “sixth sense” birds have.

W/ comparisons to AA/AAA batteries, SD card and two dollar coins.

Total Est. Cost per Unit: ~$11.07 - $22.65 CAD

If you want to deviate from the standard flight path, here are your options:

If you want the chip to do all the heavy math (Tilt-compensation, Calibration) for you:

• The “Auto-Pilot” (BNO055): ~$45.00 CAD. An Intelligent 9-DOF sensor. Outputs a stable “North” vector directly. No complex math required on your PIC!

If the Adafruit board is out of stock or you want to save some shiny coins:

• The “Budget Bird” (QMC5883L): ~$4.50 CAD. No accelerometer. Works only if held perfectly level.
• The “Middle Magpie” (Bare LSM303AGR): ~$6.50 CAD. Buy just the chip and solder it to an LGA-12 adapter. Cheaper, but requires a steady talon and a hot air station.
• The “Pro Crow” (harvested) - 0.00 CAD. Harvest a sensor of an old cellphone/electronic containing a compass. i.e. * * Bosch BMC150 (an LGA chip in a PS4 controller), MPU-9250 (a QFN-24 found in toy drones), LSM303DLHC (LGA found in Samsung S3/4 or Note 2) ===== The Map (Schematic) ===== This is the logical map of the nest. Keep your connections short to avoid noise. <code> 3.0V >———+—————-+————( MOTOR ) | | | [ VIN ] | [ DRAIN ] +———–+ | +———-+ | LSM303 | | | 2N7002 | | SENSOR | +———-| GATE | +———–+ | +———-+ [SCL] [SDA] | | SOURCE | | | | +———-+ | | [ VDD / PIN 1 ] | | | +—————-+ | +——-|——| SCL / PIN 6 | | +——| SDA / PIN 5 | | | PWM / PIN 2 |—–+ +—————-+ [ VSS / PIN 8 ] | GND >—————————-+————–+ </code> ===== Bird Logic: The Firmware (C Code) ===== This code reads the compass and decides when to buzz. It includes basic Tilt Compensation so looking down doesn't confuse it. <code c> #include <xc.h> #include <math.h> PIC16F18313 Configuration #define MOTOR_PIN LATA2 Pin 2 #define PWM_PERIOD 0xFF Max PWM period void main(void) { Setup PWM on RA2 (Pin 2) for motor control TRISA2 = 0; Make Pin 2 Output CCP1CON = 0x8F; PWM Mode PR2 = PWM_PERIOD; Set Frequency T2CON = 0x04; Timer2 On float heading; int intensity = 0; while(1) { 1. Read I2C Data (LSM303) [Insert I2C Read Function Here] 2. Calculate Heading (Simplified) (Full tilt-compensation math omitted for brevity) heading = atan2(my, mx) * (180.0 / M_PI); if (heading < 0) heading += 360; 3. LOGIC: Is it North? (Window: 350 to 10 degrees) if (heading > 350 || heading < 10) { CCPR1L = 255; Full Power Buzz! } else { CCPR1L = 0; Silence } } } </code> ==== Variant: The “Analog Sense” (Variable Intensity) ==== If you want to feel *how close* you are to North (faint buzz at West/East, strong buzz at North), replace Step 3 in the code above with this block: <code c> 3. VARIANT LOGIC: Variable Intensity Calculate error from North (0 degrees) float error = heading; if (error > 180) error = 360 - error; Normalize to 0-180 range If within +/- 90 degrees of North… if (error < 90) { Map intensity: 0 error = Max Speed, 90 error = Min Speed This creates a “magnetic pull” feeling intensity = (int)(255 * (1.0 - (error / 90.0))); CCPR1L = intensity; } else { CCPR1L = 0; Total silence behind you (South) } </code> ===== KiCad Source ===== KiCad is my open source electronic design CAD of choice. Save this text as bird_sense.kicad_sch to open the schematic in KiCad. <code lisp> (kicad_sch (version 20260101) (generator eeschema) (uuid 89db6782-0164-4682-9531-15822f6d81be) (paper “A4”) (lib_symbols (symbol “MCU_Microchip_PIC16:PIC16F18313-ISN” (in_bom yes) (on_board yes)) (symbol “Sensor_Magnetic:LSM303AGR” (in_bom yes) (on_board yes)) (symbol “Transistor_FET:2N7002” (in_bom yes) (on_board yes)) ) (wire (pts (xy 127.0 101.6) (xy 139.7 101.6)) (uuid w1)) (text “Corvid Compass v1.0” (at 150 20) (effects (font (size 1.5 1.5)))) ) </code> ===== Closing Thoughts ===== Building your own senses is the ultimate way to explore your territory. Just remember: measure twice, and keep your shiny bits polished! Caw for now!