Sunday, July 13, 2014

Ultra-Low-Power Microcontroller With A Supercapacitor

This post is a follow-up to this blog's FRAM (ferroelectric random-access memory) post in June, and takes a look at a recently-introduced Texas Instruments (TI) FRAM LaunchPad development platform, as well as how to use FRAM effectively in a particular use case.

First the FRAM development platform. It appears from a post on that the MSP430 ULP (ultra low power) FRAM board, MSP-EXP430FR5969, was soft-launched in February 2014, then rolled out with more fanfare and distributor partners in June 2014, per the Australian post, "element14 offers ultra-low power with Texas Instruments LaunchPad dev kit," and a number of other similar 'new product' posts. The Australian post above says,
"Embedded FRAM, a non-volatile memory known for high endurance and high speed write access, together with ultra low power makes the MSP430 development platform suited for a wide variety of applications ranging from metering, wearable electronics, consumer electronics and the Internet of Things (IoT) to industrial and remote sensors, home automation and energy harvesting. The new development kit includes TI's new EnergyTrace++ technology, the world's first debug system that enables developers to analyse power consumption down to 5nA resolution in real-time for each peripheral...Key features include MSP430 ULP FRAM technology-based 16-bit MSP430FR5969 MCU; 64KB FRAM/ 2KB SRAM; 16-Bit RISC architecture up to 8-MHz FRAM access/ 16MHz system clock speed; 5x Timer Blocks; Analogue: 16Ch 12-Bit differential ADC, 16Ch Comparator; Digital: AES256, CRC, DMA, HW MPY32; 20 pin LaunchPad standard leveraging the BoosterPack ecosystem. Various components including on-board eZ-FET emulation for programming, debugging and energy measurements have been provided in the evaluation kit for a fast start; on-board buttons and LEDs on the board enable quick integration of a simple user interface in addition to a SuperCap allowing standalone applications without an external power supply."
MSP430FR5969 LaunchPad Power Domain Block Diagram
The part that especially interests me is the SuperCap that enables a minimal level of operation without an external power supply (and without a battery?). Enabling MCUs to operate without external power sources was the topic of an earlier post on this blog, "Microcontrollers: Batteries Not Included. Or Needed." That post discussed getting the MCU's power from small energy harvesting devices. It would be nice if a supercapacitor turns out to be another no-batteries-needed option for MCUs. The board's User's Guide shows the power domain block diagram to the left and says, "The board is designed to support five different power scenarios. The board can be powered by eZ-FET or JTAG debugger, external power, BoosterPack power, or standalone super cap power." A bit of online research is needed, it appears, for me to totally understand just how much the MSP-EXP430FR5969 board can do using just the 100 mF capacitor and no external power. If Google and I can't figure that out, I'll check with Ed Smith to get my answer!

If you're interested in the MSP430FR5969 microcontroller (MCU) that powers the above development platform, consider reading the Electronics Weekly article, "Exploring FRAM microcontroller-based design – Texas Instruments." The graphic at the right from that article shows how flexible the memory configurations are in that MCU. Here are a few more resources to help you learn more about the MCU and its platform:
  1. MSP430FRxx MCU overview page on TI's site.
  2. MSP-EXP430FR5969 LaunchPad Evaluation Kit page on TI's site.
  3. Overview of MSP430 Ultra-Low-Power MCUs PDF on TI's site.
  4. MSP-EXP430FR5969 LaunchPad Development Kit User's Guide PDF on TI's site.
  5. 6-part video tutorial on YouTube for the MSP-EXP430FR5969.
If you want to buy the MSP-EXP430FR5969 kit, I'd suggest you consider either direct from TI ($24.00) or from Newark ($24.05). Octopart gives a good look at the price spread and availability of the kit, with costs ranging from TI's $24 up to more than $39 from Arrow. The 43oh post above shows one way manufacturers entice hardware developers to buy newly released components. For $5 extra ($29 for the kit instead of $24), when you ordered the MSP-EXP430FR5969 kit from TI when it first came out, you got both the kit and a "LS013B4DN04
SHARP Memory LCD display...1.35″...96×96 pixels wide...booster PCB has touch capability, with touch strips on either side of the LCD" which retailed for $18. I don't know if $5 for that LCD is a better deal than the small LCD Ed Smith had at the Humboldt Microcontrollers Group meeting last week, but the touch strips would have made it an interesting component with which to experiment. Element14 also has a road kit for the board which includes the same LCD.

The other part of this post was going to be on an ideal use case for the MSP430FR5969 MCU's FRAM. However, I wrote more about the TI development kit than I planned on, and I'm being mindful of feedback I got that said (at least some of) my posts were too long. So for people interested in reading about that use case right away, here's a link to the article about the FRAM-MCU application I mentioned at the start of this post. I'll discuss that use case in tomorrow's post, and maybe have a couple other examples of good applications for an MCU that doesn't pull much amperage and has FRAM. If you read the FRAM-MCU application article, send me your comments and questions regarding that article -- arcatabob (at) gmail {dott}com. Thanks!


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