The heart of the logic of this kit is based on a small AVR microprocessor. The selection for a chip in the AVR range is only based on previous experiences with AVRs, and therefore the availablity of software, programmers, and knowledge. A PIC microprocessor should probably also be able to do the job.
The AVR selection was based on the following criteria:
Low voltage, minimum 1.8 Volt was preferred over 2.7 Volt, as we thought of using two AAA batteries
Maximum memory taken the criteria above into account
By using the AVR Compare Devices page (Well done!) we selected the ATtiny85V, which has only 8-pins in a DIL housing, a suuply voltage down to 1.8 Volt, and the maximum memory in this range.
The ATtiny85V has two 8-bit timers, where one is used for the morse audio tone and the other as a random number generator to randomly select new 'secrets words'.
Speaker Selection
We looked for a small speaker, being a speaker and not a piezo buzzer. With a real speaker you are able to change the tone frequency, which is not possible with a piezo.
The speaker selection was based on the following criteria:
Low price
Easy to mount on a PCB by just soldering
Availability on the semi long run (in case more kits have to be produced)
Reasonable sound production, both in volume and in tone clearness.
It is hard to find small PCB mounted speakers that are not piezos. We found one at Baco in IJmuiden, and one at Farnell. Because of the slightly better tone and the availablility of 16000, we select a small PCB mounted speaker from Farnell.
PCB
To be added here.
Software
The AVR software was developed with Atmel Studio, and therefore written in the C programming language.
Morse tone using PWM
To be added here :-).
Encoding the morse words and program into 512 kB
To be added here :-).
Pictures and movies
All electronic components.
The batch of 30 PCBs arrived from China.
Movie of a ready badge with a small explanation in Dutch (original video on YouTube).
Improvised movie (in Dutch) of the prototype, taken during a JOTA preparation meeting.
"Share Your Morse" badge prototype: Software testing.
A project by PA1IVO and PA0LEZ.
The heart of the logic of this kit is based on a small AVR microprocessor. The selection for a chip in the AVR range is only based on previous experiences with AVRs, and therefore the availablity of software, programmers, and knowledge. A PIC microprocessor should probably also be able to do the job.
