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Understanding the NXP i.MX6UL Pin Mux

(note, the article is also applicable to the i.MX6ULL as these processors are very similar)

The NXP i.MX6UL application processor has a very flexible pin multiplexer, that is somewhat difficult to understand at first glance.  Most times when we’re configuring the pin mux in Linux, we modify Device Tree files, so perhaps that is the place to start.  The pin mux options for the i.MX6UL are defined in the arch/arm/boot/dts/imx6ul-pinfunc.h file.  The arguments to the macros in this file are defined as:

/*
 * The pin function ID is a tuple of
 * <mux_reg conf_reg input_reg mux_mode input_val>
 */
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IOT Protocols: MQTT vs CoAP vs HTTP

With the explosion of IOT (Internet of things), there are now more technologies we can use to build systems.  In reality, we’ve been doing IOT for years.  We’ve been networking devices for a long time.  We’ve been collecting data from remote nodes.  This is nothing new, but what the IOT movement brings to the table is technologies that are much lower cost, and more standardized.  Two of these technologies are MQTT and CoAP.  Both very interesting, and very useful.  Recently, I helped a system manufacturer think through the architecture of a system with the following requirements: