Vermes
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Presented device is a WAV audio files player. It was realized based on Atmega32 microcontroller, despite the charge size is about 8-9kB. Program was written in C. The player supports any memory cards MMC/SD (including MicroSD, which can be inserted in adapter, as showed in the pictures). Two cards are used here: one with a capacity of 32MB and MicroSD 2GB placed in the blue adapter.
The player supports alphanumerical LCD display 2x16, on which there are current information displayed, such as: operation mode (play/stop), volume (adjusted in the range of 1-4), the exact duration of the track minutes and seconds as well as the name of played WAV file).
The whole is powered by +3,3V. The system additionally supports 3 keys and 8 LEDs which are simply control indicator.
Schema:
The system has two keys to change the volume in four simple ranges from 1 to 4. Additionally, there is also one NEXT key, that is used to switch to another track.
Speed of sampling in this player is maximum 22,050kHz. But the device plays WAV files with any smaller sampling, both STEREO and MONO.
Hardware SPI is used to communicate with SD card. The processor is clocked by 16MHz quartz. Playing stereo is supported by two PWM outputs of Timer1 (OC1A and OC1B). There are capacitors 100nF connected to the pins outputs.
Program works based on PetitFAT.
