TSL2550 with Microcontroller

The TSL2550 Ambient Light Sensor simplifies the acquisition of ambient light intensity and spectral content information through the use of on-board analog-to-digital conversion and SMBus interface. Targeted at laptop PCs and other portable computing devices, the TSL2550 measures ambient light for the purpose of adjusting display backlighting for minimum power consumption. Intended for use with standard SMBus controller chips, the TSL2550 may also be interfaced with standard microcontrollers without dedicated SMBus ports. This application note provides a detailed overview of how to implement SMBus communication using standard I/O ports on a microcontroller.

Engineers and programmers beginning an SMBus project - such as for the TAOS TSL2550 - will immediately recognize the similarities between the SMBus specs and those of I²C. Those fortunate enough to be programming microcontrollers with built-in I²C functions need do little more than heed the SMBus' additional timing restrictions. They may then go their merry way exchanging data with an 8-bit peripheral port, blissfully unaware of each transaction's details. But the rest of us, programming low-end PICs (www.microchip.com) and SXes (www.ubicom.com) for example, need to be aware of every nuance of every SMBus read or write. We're bit-bangers. This is our story.