The Morse-Cache

Description:

Make your geocache more interesting with the Morse-Cache!. When triggered, it outputs a sequence of numbers in morse code. The Morse-Cache also indicates via an adjustable battery warning when his batteries should be replaced. Besides this, the Morse-Cache is low power and fits even in small cases. Perfect for multicaches!

Features:

• Output a morse code sequence

  • Sequence consists of a maximum of 61 numbers

  • Preservation through firmware updates

• Triggered by magnets (through a reed switch)

• Configurable battery warning (See Usage)

• Automatic self-test after reset and poweron (See Usage)

• Low space and power consumption

• Runs with 2x AA or 2x AAA batteries (recommended)

Usage:

Trigger the Morse-Cache:

1. Hold the magnet over the magnetic switch (reed contact).

2. When the Morse sequence is displayed, remove magnet.

3. After the Morse sequence has finished, the device can be triggered again.

• Color of the LED (should be noted in the listing of the geocache):

  • Green: Normal color of the LED

  • Red: Battery low, should be replaced

Adjust the battery warning:

1. Connect the circuit to a stable voltage source between 1.9V and 5V whose voltage sets the new limit from which the battery is considered empty.

2. Holding the calibration button while triggering the magnetic switch.

If the morse code sequence is displayed, repeat step 2 after the end of the sequence (first hold the button, then trigger the magnetic switch)

3. Release the calibration button when both LEDs light up briefly.

   • If both LEDs remain dark, check voltage source and repeat step 2.
   • If only the red LED lights up, increase battery warning voltage limit.

Releasing the magnetic switch after the LED goes off will display the morse code sequence

4. Device is ready for use.

Issuing the self-test:

1. Press the reset button.

The Morse-Cache must not be in the calibration process

2. If the LED lights up briefly, the self-test was successful, else the internal EEPROM memory of the Morse-Cache may be corrupted.

A defective Morse-Cache should be repaired before used again!

Building the device firmware:

1. Clone the Git Repository.

2. Type cd source.

3. Building the firmware with avr-gcc using make all (Use make hex to generate a Ihex-file).

4. Use make size to check the size of the binary (max 1024 on ATtiny13/A).

5. Use make fuse to check the fuse values (usually 2afd).

6. Use make program to flash the firmware with avrdude (you may need to adjust AVR_PROGRAMMER and PORT).

7. Use make clean to clean up.

Updating the device firmware:

Only possible with programming adapter

1. Check for new version.

2. Downloading the newest version (.elf file).

3. Flash the .elf file with a programming adapter (USBasp, ...).

Changing the Morse sequence:

Only possible with programming adapter

1. Use the eeptool.py for creating the desired morse code sequence.

2. Burn the resulting binary file in the EEPROM of the Morse-Cache.

You may readjust the baterry warning

Additional notes:

Supported Devices:

• ATtiny13

• ATtiny13A (recommended)

Fuses (ATiny13/A):

• hfuse: 0xFD

• lfuse: 0x2A

Morse code characteristics:

EEPROM address range:

• Start: 0x00

• End (maximum): 0x3D

Characteristics:

• The string must be terminated (at adress 0x3D at the latest) with 0x00.
• Only numbers between 0x30 and 0x39 (0-9) are accepted data values.

Invaild data will be ignored!

Battery warning mechanism:

• The current ADC output is compared with the value inside the EEPROM.

EEPROM adress range:

• high byte: 0x3F
• low byte: 0x3E

Built with:

• avr-gcc - compiler
• avr-libc - runtime libary
• avrdude - programming software

License:

This project is licensed under the GPLv3 License - see the LICENSE file for details

Authors:

• Armin W. Wer-Wolf

Acknowledgments:

• The idea how to store the morse code was discovered in the Mikrocontroller.net Forum.