Friday, November 15, 2013

Sparkfun vs1063 DSP breakout

The Sparkfun vs1063 breakout gives you a vs1063 chip with a little bit of supporting circuit. You have to bring your own microcontroller, sdcard or data source, and level shifting.

One thing which to my limited knowledge seems unfortunate is that the VCC on the breakout has to be 5v. There are voltage regulators on the vs1063 breakout which give it 3.3v, 2.8v and 1.8v. Since all vregs are connected to VCC and it wants to make its own 3v3 then I think you have to give 5v as VCC on the breakout board.

With the microsd needing to run on 3.3v I downshifted the outbound SPI ports, the sdcard chip select, and the few input pins to the vs1063 board. Those are the two little red boards on the breadboard. The sdcard is simply on a breakout which does no level shifting itself. The MISO pin is good to go without shifting because a 3.3v will trip as high on a 5v line. Likewise the interrupt pin DREQ which goes to pin 2 on the Uno doesn't have any upshifting.

I had a few issues getting the XDCS, XCS, and DREQ to all play well from the microcontroller. A quick and nasty hack was to attach that green LED in the middle of the photo to the interrupt line so I could see when it was tripped. During playback it gives a PWM effect as 32byte blocks of data are shuffled to the vs1063 as it keeps playing. The DREQ is fired when the vs1063 can take at least another 32 bytes of data from the SPI bus to it's internal buffer. Handy to have the arduino doing other things and also servicing that interrupt as needed.

I'm hoping to use a head to tail 3v3 design for making a mobile version of the circuit. I would have loved to use 2xAA batteries, but might have to go another way for power. Unfortunately the OLED screen I have is 5v but there are 3v3 onces of those floating around so I can get a nice modern low power display on there.

The next step is likely to prototype UI control for this. Which I'll probably use the 5v OLED in the meantime to get a feel for how things will work. I get the feeling that an attiny might sit between the main arduino and the parallel OLED screen so it can be addressed on the SPI bus too. Hmm, attiny going into major power save mode until chip selected back into life.

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