An Introduction to Microcontrollers, Part Ⅶ: I2C Interface Links Math Chip and MCU

摘要

This article continues the Micromega uM-FPU V3.1 floating-point math-IC discussion, explains how to connect the FPU IC to an MCU (microcontroller) and use it, and provides testing and troubleshooting tips. When you need math that involves trigonometric functions, logarithms, multiplication, and division of large and small numbers, the add-on FPU V3.1 IC can seem like a miracle. That goes double if you need matrix or fast Fourier transform (FFT) operations. The uM-FPU V3.1 math IC, which I'll call the "FPU IC," allows connection to an MCU via a Serial-Peripheral Interface (SPI) or an Inter-lntegrated-Circuit bus (I2C). I chose the I2C bus created and standardized by Philips Semiconductors, now part of NXP. You can find many microcontrollers, sensors, analog-to-digital converters, memories, and clocks that operate with I2C interfaces. Unlike SPI connections, the I2C bus lets software easily address individual ICs and their registers. The FPU IC, for example, has a fixed address of 1100100X_2. A 0 in the X-bit identifies a write to a slave device from an MCU, and a 1 in that position requests data from a slave.