The Teensy Audio board has space for an 8 pin SPI flash memory chip; this is much faster than playing directly from the SD card, and thus allows for more concurrent samples to be played at once. (From testing, playing from the SD card allows for about 2 sample polyphony, whereas the SPI chip is around 12+). The only problem is that the 8 pin footprint limits the capacity of the chip; the largest that I have seen is the 16MB Winbond W25Q128FVSIG chip.

Since 16MB is too small for a complete set of samples, I had designed support for a larger Spansion S25FL512SAGMFI011 chip onto the Drum Master board; this gives me 64MB, which should be more than enough for a complete set of samples. (You can then switch between samples by loading samples off the SD card onto the SPI chip).

I had not tried to use the new chip until today; I was having too many problems with the analog part of the circuit. However, today I figured that I should verify the other parts, prior to ordering new parts for the analog bits (if I need to buy other components, I would rather do it at the same time and not pay shipping twice).

However, for the life of me I couldn't get the large SPI chip to work. The logic analyser showed what looked like a floating line on the CS pin; I was getting all sorts of noise.

(This is my testing setup... wires, wires, everywhere!)

Finally I thought to pull up a schematic of the Teensy Audio board.

Turns out that the pin I was using for the large SPI flash memory CS was pin 15, which was allocated for the audio board's volume control pot. I had not soldered a pot on, so I figured it was fine. However I had missed the 0.1uF capacitor which was included on the board.

In case anyone is following along at home, the capacitor you need to remove is this one:

A quick desolder job and the 64MB SPI flash chip is now working perfectly.