Summary

This project is a write up of a gift from a friend for my birthday.

Using a hardcoded set of latitude and longitude coordinates, if the device is further than 500 meters away a red light shows, if between 500 and 50 a yellow light, and less than 50 meters a green light shows.

Distance is calculated using the haversine formular to calculate a "crow-flies" distance, that takes into account the curvature of the earth, just in case you try and go hundreds of miles away :-)

Technology

It uses an Atmega88-20pu and 16mhz crystal resulting in what I understand to be an Arduino on a breadboard with a few minor differences due to the difference in chip specifications.

The key differences between the Atmega88 and atmega328 found on typical Arduino devices are;

• Lower Flash: 8192 vs 32768 bytes
• Less SRAM: 1024 vs 2048 bytes
• Smaller EEPROM: 512 vs 1024 bytes
• No temp or pico power options

Consult the respective datasheets for more detailed comparisons.

Bill of Materials

For this project you will require the following components, however you should be able to easily replicate the design using a typical Arduino device without too much hassle.

• AtMega88-20PU DIP
• 1x 10uf Capacitor
• 2x 27pf Capacitors
• 1x 16mhz crystal
• 3x coloured LED's (Red, Yellow, Green)
• 3x 470ohm resistors
• 1x 10k ohm resitor
• 1x gy-gps6mv2 GPS module
• 2x AA batteries
• 1x 30x12 breadboard with power lines (Give or take)

Build Instructions

Flash the chip

To push the code onto the Atmega88 its easiest to use an Arduino in ISP (In System Programmer) mode.

Specific instructions are not provided as I haven't tried it yet - my mate did the initial programming.

Conditional Flags

Due to the reduced footprint of the AtMega88 chip, the low-power and serial debugging options are enabled using some compile time flags, (DEBUG/LOW_POWER_MODE), to reduce consumption to < 8k - Normal arduino chips shouldn't require these flags to be disabled

Schematic

Until I find something that helps me show proper layouts, heres a photo. Ignore the brown wire at the bottom left; this was left over from some experiments that didn't go anywhere.

Wire up the Atmega88

1. Place the atmega88 in the middle of your breadboard
2. Place the 16mhz crystal across XTL1 and XTL2
3. Place the 27pf capacitors from each leg of the crystal to ground
4. Place jumpers between each of the chips ground pins and the ground plane
5. Place the 10k resistor between the positive plane and the reset pin of the atmega88
6. Place the 10uf capacitor between the positive and ground planes - ensure you check the polarity
7. Place jumpers between vcc, vRef and AVcc
8. Place jumps from the positive plane to the vcc pin

This should leave your breadboard with an Arduino-ish clone with nothing really wired up to do anything apart from start if you apply 3v to the power lines.

Add the GPS and LED's

1. Add a 470ohm resitor and the green led between Digital output 5 and the ground pin
2. Add another 470ohm resitor and the yellow led between Digital output 6 and the ground pin
3. Add the last 470ohm resitor and the red led between Digital output 7 and the ground pin
4. Attach the GPS module to the breadboard and connect:
   1. GND to the ground plane
   2. The TX from the module to the RXD input on the Atmega88
   3. VCC to the power plane