By: Peter Stonard, Technical Marketing Manager, NXP Semiconductors
Regardless of the application or size, all industrial systems that incorporate electronic controls or monitoring face a similar problem – how do signals flow between sections, under harsh factory conditions? One established solution is also the most simple: a two-wire slow speed digital bus, called I2C.
Perhaps the heart of your system is a metal enclosure, rugged, and ready for the factory floor? Or, the pieces of your system are spread out, and interconnected with electrical cables? Perhaps you need to know about the real world, with limit switches or temp sensors? Or, a human operator is reading your data on displays, and pressing buttons manually.
In all of these cases the major components must be interconnected in a reliable and simple way, to keep down costs and improve reliability. The I2C bus, and the vast array of available direct connect I2C bus components, is a sure solution to your interconnect needs.
Although the I2C bus has been around for a long time (back to the 1980s), it remains a popular answer to today’s slow speed (up to 1MHz) digital data interconnections, and uses only two wires (clock and data). There are LCD and LED controllers, temp sensors, and GPIO (General Purpose Input/Output to read many single switches or LEDs), plus when the bus must go further than the originally intended single or small cluster of PCBs there are bus buffers to boost the signal.
An important hurdle in system design, which is often built around a specific core (CPU, MPU), is the fear of running out of IO ‘pins’ or channels. GPIO is a handy solution, offering the designer many new pins by extending the existing I2C bus with one or more GPIO devices. Better yet, the latest offering of GPIOs operate directly from low voltage IO pins on today’s CPUs and MPUs.
An often overlooked but important feature of industrial systems is time keeping, important because as data moves around, the timestamp has to remain valid and accurate. With an accurate and stable Real-Time Clock (RTC) that consumes little power, uses minimal board space and has a local battery backup, savvy designers will save the day in the event of utility power loss.
Over the life of the I2C specification, many electronic components have been introduced with much lower supply and signal voltage requirements; in particular, more powerful CPUs and MCUs operate from one to two volts instead of the five volts in vogue when I2C was invented. The NXP I2C catalog includes many voltage level translators to bridge these disparate needs.
For those harsh industrial systems there is something new, a more robust interconnection using the same protocol combined with the known reliable addition of differential signaling – called dI2C. Take a look at PCA9614, the easy way to upgrade I2C in an electrically noisy application.
Popular I2C devices for industrial systems are below:
|Application||NXP Part Number|
|DIFFERENTIAL BUS DRIVER||PCA9614DP, 118|
|LCD DISPLAY DRIVER||PCF8553DTT/AJ|
|I2C BUS BUFFER||PCA9617ADPJ|
|LEVEL TRANSLATOR||GTL2002DP, 118|