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MSP430 vs Silicon Labs efm32

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Hi,

 

Sorry if it's a repeated question, but I am in the middle of a meeting and I am looking for pros and cons of MSP430 vs EFM32. For low-end, low activity, low cost, ulp devices, it appears to me that EFM32 beats MSP430 hands down; but that may be impulse buying. What's the catch?

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I think it'd depend on duty cycle and requirements, and how much effort gets put into the software design. My impression is MSP430 will be cheaper and EFM32 has more capability and is faster. The Wolverine (e.g. MSP430FR5969) has really low power, comparable to Zero Gecko; I'm seeing 250 nA for LPM3.5 with an EXP430FR5969 application that wakes periodically on RTC alarms. I expect to have numbers from an apples-to-apples comparison between the two in the next week or two.

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I think it'd depend on duty cycle and requirements, and how much effort gets put into the software design. My impression is MSP430 will be cheaper and EFM32 has more capability and is faster. The Wolverine (e.g. MSP430FR5969) has really low power, comparable to Zero Gecko; I'm seeing 250 nA for LPM3.5 with an EXP430FR5969 application that wakes periodically on RTC alarms. I expect to have numbers from an apples-to-apples comparison between the two in the next week or two.

@@pabigot Can you take notes, if possible with pictures. It will be nice to see a comparison.

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Do you mean c8051 by TI? That's an interesting trend to know, but not sure what you mean by that.

I just put in '8051' and that's the curve it gave.  The dropoff is quite a bit sharper than it is for msp430.  Just for kicks, go there and put in 'Arduino' and 'Raspberry Pi', and you'll understand how rapid and popular RPI has become.  Interesting stuff.....

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EFM32 has historically been quite expensive, which has prevented most designers I know from using them.

 

Anyway, EFM32 definitely has great features for using with a low power RTOS.  If you are simply throwing code onto asynchronous interrupts, MSP430 might work better for you.  I should also add that FRAM doesn't really have the same advantage when any sort of timer-based wakeups are used as a critical part of the system (e.g. an RTOS scheduler timer), due to the way the timing and clocking system is architected with the FRAM MSP430s.  If you have a system with line interrupts, FRAM can be pretty great, albeit expensive.

 

EFM32 is also more efficient than MSP430 during code execution by a landslide.  So if you are doing 1/1000 duty cycle or more on your MSP430, you will get a decent energy saving by switching to the EFM32, even if you are comparing against Wolverine parts.  I guess it goes back to the same point in the last paragraph: if you are stuffing code onto asynchronous interrupts, that's where MSP430 is technically becomes a good option.

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How so?

The rest of the post should explain that.

 

To clarify: MSP430 doesn't run code as efficiently as CM3 does.  The more code that runs, the more advantage a low-power CM3 has.  If I run a scheduler or whatnot, that has a tangible impact on power usage.  Moreover, running a timer tends to require the ACLK domain is on, which IIRC doesn't allow lower than LPM3.  If you have a pure asynchronous app, you can use LPM3.5 and maybe even LPM4.

 

If you are trying to build a sophisticated app with low power, it's like spinning plates to an extreme degree, but for networking "IoT" kinds of things I've had better results using STM32L than I have had with any MSP430.  EFM32 is technically superior to STM32L, so I have to imagine it would work nicely.

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How so?

The lowest power modes disable clocks but still allow the CPU to be woken up by pin interrupts. So the MSP430 still has an edge in cases where it sleeps for seconds, hours or even days before being woken up due to an external event.

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The EFM32 has something they call a "peripheral reflex system", which as I understand it allows completion of one peripheral action to cue another without MCU involvement. Something like DMA, but generalized.

 

Hand waving; I haven't gotten to that point in my experiments yet. But in concept I believe this is supposed to be more efficient than the MSP430 interrupt-driven approach, or less limited that MSP430's trigger mechanism.

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