Lookup table and volume

Hello Jack,

The difficulty appears to be not in the lookup table itself, but with the integer index which drives it. The rotary encoder conditioning block converts the quadrature encoder output to "up" and "down" pulses, so it was logical to try the circuit described at https://ez.analog.com/message/145882#145882 to generate an index from these pulses. However, that circuit needs some modification to work here. It was intended to operate with straight push-button inputs, where holding a button down would slowly increase or decrease the index. This is done with an integrator scheme (the summation block with feedback adding to itself) which changes the index over time. The encoder conditioning block, however, outputs very narrow "up" and "down" pulses. These pulses are too short to move the integrator output very much, so you get little or no volume change as you rotate the encoder.

The best implementation would involve a digital up-down counter block, however I could not find any in the toolbox other than the GPIO button block, which I could not get to work. Thus I went back to the integrator, while modifying it to work with the one-sample wide pulses from the rotary encoder conditioning block. The resulting arrangement is pictured below:

The integrator now counts in increments of 0.25 in standard analog 5.23 format (which is 1's in 7.21 format). This is converted to integer (28.0 format) to drive the lookup table. You can use your original table with 33 values, or a larger one up to a max index of 63. I tested this project on a ADAU1701MINIZ eval board. Since this board uses I2C instead of SPI and has different MP pin usage, I did not attach the modified project here.

Best regards,

Bob

Bob,

It works great.

Thanks a lot!

Regards,

Jack