In the last video I demonstrated a Universal Active Filter that I could adjust with a dual-gang potentiometer, here I replace the potentiometer with a processor controlled solid-state potentiometer. For those that are too young to remember, we used to say “solid-state” to differentiate between that and something that used vacuum tubes… mostly we meant you could drop it without it breakage.
The most common way to control the everyday peripheral chips available is through use of one of the common Serial Protocols such as I2C and SPI. In the before-time back when we had only 8 bits and were lucky if 7 of them worked, we used to have to memory map a peripheral or Input/Output (I/O) controller which means we had to take many control and data lines from the microprocessor such as Data, Address, Read/Write, system clocks and several other signals just to write to a couple of control registers buried in a chip.
Nowadays there is a proliferation of microcontrollers that tend to have built-in serial interface capability it is pretty straightforward to control a full range of peripheral functions; digital and analog alike. Rather than map each peripheral using said data and address lines,which is a very parallel approach, the controller communicates with peripherals serially using but a handful of signal lines such as serial data and clock. A major task of old system design, mapping of I/O and peripherals, is no longer needed.
Continue reading “We Assume Control: SPI And A Digital Potentiometer”
Before using the TI though, [Inderpreet] wanted to test with the Bus Pirate first. This would allow him to verify the hardware, and to make sure he was correctly using the I2C bus. The Bus Pirate can operate at 3.3V or 5V logic levels, and has on-board programming specific to the I2C bus. Controlling the Bus Pirate is as easy as hooking up a serial terminal program and plugging in a USB cable.
