Finding the limit and power saving

Well I’m definitely going to make a 20MHz ATmega328p version just to discover where the limit lies with FLAC. Scratch that… apparently Atmel is working with ‘speed grades’ these days, or in other words “Maximum frequency is dependent on Vcc”. Reaching 20MHz requires at least 4.5V and this poses a bit of a problem since all other components require 3.3V or less. Guess this also explains why the 3.3V Arduino Pro Mini board only comes at 8MHz.

In the mean time I’ve been working on getting some basic functionality to work. Currently working are play, pause and stop playback, play next song, continues playback (instead of just 1 song for testing purposes which got a little repetitive after a while ;)), volume control (up, down and mute) and a debug function outputting decode time, samplerate, bitrate and type of file.

Atm I’m trying to get sleep modes working. Also new is card detection. When no card is inserted the AVR goes into the 0.1 uA power down mode. Insert a card and it starts playing. Not fully working yet , but it’s getting there. Also when playback is stopped it should go into idle mode until the play command is received (saving 4 mA).

A command I haven’t got a clue yet on how to implement is shuffle. If anyone has a suggestion,  feel free to add a comment.

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