Self-healing mesh networks on the 8-bit Industrial Internet

April 13, 2017 Brandon Lewis, Technology Editor

One of the most interesting stories in the embedded processing market over the past decade has been not just the survival, but in many ways the triumph, of 8-bit microcontrollers (MCUs). Indeed, market data from iSuppli (now part of IHS) shows not only has the 8-bit MCU market continued to grow through this year, but it has nearly kept pace with the 32-bit market and done so in spite of tapering 16-bit sales.

[Figure 1 | The 8-bit MCU market continues to flourish despite long-held beliefs to the contrary.]

Now, however, the technology industry is fully enveloped by the Internet of Things (IoT), which carries with it the prerequisite of connectivity, and in many cases security as well. The memory requirements alone for these functions often prove substantial for many modern 32-bit MCUs, much less legacy 8-bit products that often max out at 256 KB flash memory and 8 KB RAM.

Surprisingly, though, these factors have not limited the deployment of 8-bit MCUs in IoT applications for multiple reasons. On one hand, the IoT has enabled electronics in devices where one would never find them before (such as pens and shoes), while on the other, many IoT systems still just don’t require more than what an 8-bit MCU has to offer.

“There are a ton of applications that you can run on an 8-bit and have it be ‘enough’,” says Steve Kennelly, Senior Product Marketing Manager for the MCU08 Division at Microchip Technology, Inc. “There are a lot more MCUs in ‘things’ today, so while 8-bit MCUs are holding on longer than anyone expected, that’s going to continue.”

While cost and power consumption remain the key drivers of 8-bit processors in IoT applications, features like core independent peripherals (CIPs) and code optimization have enabled MCUs like the 8-bit PIC18F46J50 (Figure 2) to continue operating as the brains of IoT systems. For example, the MRF24J40MA module (Figure 3) at the heart of a Microchip MiWi Self-Healing Mesh Network is based on the PIC18F46J50, which includes only 64 KB of flash memory and less than 4 KB RAM.


[Figure 2 | The PIC18F46J50 is an 8-bit Microchip PIC MCU that contains 64 KB of flash and less than 4 KB of RAM, but is still viable in mesh networked IoT applications.]


[Figure 3 | The MRF24J40MA module is an 802.15.4-compatible radio transceiver module that supports PIC MCUs.]

The MiWi Self-Healing Mesh utilizes a lightweight 802.15.4-based protocol that consumes less than 30 KB of memory, leaving enough code space for savvy engineers to develop simple but effective applications for the industrial, commercial, building automation, and other sectors that stand to benefit from mesh networking.

In the below video, Stephen Porter, Software Manager, Wireless Solutions Group at Microchip, explains.

[youtube=https://www.youtube.com/watch?v=Hdyqju91CtI]

Perhaps more than anything else, the MiWi Self-Healing Mesh demo illustrates that the IoT is based more on cost, power, and ease of use than the speeds and feeds that have consumed the electronics industry in the past. This is a good indicator that 8-bit MCUs will keep filling a market need for the foreseeable future.

All of Microchip’s 8-bit PIC MCUs that support the MiWi Self Healing Mesh are listed below.

PIC16F18857 PIC18F27J53 PIC18F87J93 PIC18F8527
PIC16F18877 PIC18F66J94 PIC18F96J94 PIC18F6622
PIC18F26K20 PIC18F86J16 PIC18F66J65 PIC18F8622
PIC18F66J11 PIC18F66K22 PIC18F87J94 PIC18F6627
PIC16F19197 PIC18F66J55 PIC18F87K22 PIC18F8627
PIC18F46K20 PIC18F67J90 PIC18F67J60 PIC18F6525
PIC18F66J16 PIC18F46J53 PIC18F86J60 PIC18F6722
PIC18F26K22 PIC18F86J90 PIC18F87K90 PIC18F6628
PIC18F67J11 PIC18F47J13 PIC18F97J94 PIC18F8525
PIC18F26J11 PIC18F67J50 PIC18F2515 PIC18F6621
PIC18F46K22 PIC18F87J11 PIC18F86J65 PIC18F8722
PIC18F66J15 PIC18F66K90 PIC18F96J60 PIC18F8621
PIC18F26J13 PIC18F67J93 PIC18F87J60 PIC18F8628
PIC18F26J50 PIC18F86J50 PIC18F4515 PIC18F6723
PIC18F67J10 PIC18F86J93 PIC18F2525 PIC18F8723
PIC18F46J11 PIC18F67J94 PIC18F96J65 PIC18F6620
PIC18F26J53 PIC18F67K22 PIC18F97J60 PIC18F8620
PIC18F86J15 PIC18F86J94 PIC18F4525 PIC18F6720
PIC18F27J13 PIC18F47J53 PIC18F2610 PIC18F8720
PIC18F66J90 PIC18F86K22 PIC18F4610 PIC18F26K42
PIC18F46J13 PIC18F86J55 PIC18F2620 PIC18F27K42
PIC18F87J10 PIC18F87J90 PIC18F86J72 PIC18F46K42
PIC18F46J50 PIC18F66J60 PIC18F4620 PIC18F47K42
PIC18F66J50 PIC18F67K90 PIC18F87J72 PIC18F56K42
PIC18F86J11 PIC18F87J50 PIC18F6527 PIC18F57K42
PIC18F66J93 PIC18F86K90

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