Playing wave files using arduino, SD card and speaker

What are you doing to make the Digital To Analogue Converter (DAC) - if you have an 8 bit .wav file you've got 8 digital connections to make but you only mention 1.

(There are ways it can be done with only 1 pin but I don't think you are doing this from your description.)

MK

That's a very good question. I don't know. The idea that it can be done was based on numerous examples on the Web and on YouTube showing it done exactly like that using not only the atmega328 but also using an attiny85.

So,I'm missing a DAC? any way it can be done without it, or at least improvised? I'll get a DAC if that's the way to go, but have a deadline I can't really push (birthday :-)

If you want decent sound quality you need a proper DAC. If you are good at software you can make PWM DAC using a digital output pin and  a low pass filter  - you will need some kind of amplifier to drive  speaker.

If there are projects on the web and you are in a hurry why not just copy one.

I don't think you'll be able to decode mp3 in real time using an Arduino (but you can buy chips that will and can be controlled by an Arduino).

MK

A. not trying to decode mp3. Trying to play WAV files.

B. The library I mentioned (and several others)  do exactly that - use pwm in software. It works, but the volume is low and choppy. So the low pass filter and amplifier that's missing was exactly my question.

Problem is: values to use for resistor/capacitor of low pass filter and what type of amplifier exactly.

I can't see any reference to the software in your earlier posts but never mind -  the important thing is the PWM frequency being used - if the code has any documentation a link would help.  Did the project you're modifying have come with a schematic - is so could you link to it or post yours.

If you are trying to drive a speaker you need an audio power amplifier, something like an LM386 or LM380 should do.

You do need a filter between the processor pin and the amplifier.

I see that you tried an LM386 but it didn't work  - should have at least made more noise so the next question:

Do you have any test gear ?

MK

Wow, sorry about that. The library in use is the tmrpcm library . https://github.com/TMRh20/TMRpcm. My bad.

Yes, I've tried using an LM386 but it didn't work. It made no sound at all. Tried without a filter.

I wanted to know if it were the course to go before trying to arrange a test.

My intention is to try and use the LM386 to amplify simple audio from a headphone jack to make sure I got it right.

I'll give that a try, and get back to you.

It was important to me to get a preliminary approval for the general course of action -  processor pin pwm - to low pass filter - to opamp - to speaker

Long story short got it working. And in time to give the birthday present, well, on the birthday.

A. Used a SparkFun mono amp breakout board. Turns out I asked for LM386 at the store and got LM358N,which are no good for audio amplification, and I didn't have the necessary parts to try and build one anyways.

B. First I thought using a 9v battery and one 5V regulator for the atmega328 plus one 3v regulator for the logic level shifter and the SD. BUT, the 7805 uses the battery even when the arduino is put to sleep (power down, reset connected to button for wake up), so I went with 2 1.5 AA batteries. The volume is lower, but I've built a small enclosure for the speaker from cardboard, and it's good enough for one listener in a quite room, which was the purpose.

Thanks a lot for your help. Turns out it was quite simple.

Glad you got it going - there's nothing (well not much) worse than buying in some special part and getting the wrong thing. I think it happens about 1 part in 100. I have 50 TL082 chips here (dual op amp) in a packet with a label saying MC74BLX4052 - luckily I didn't have the board to solder them to and they were replaced quickly.

MK

Hi, I know this thread is from some time ago, but would you be willing to share the code, if you still have it.

I would like to do something similar to your project.

Thank you.