Opinions on Silabs EFM32ZG?

[madshaman]

Hi, anyone ever messed with these?

Honestly, I just want to see what kind of fun doohicky I can make which takes almost no power; was thinking of ordering an eval board.

I don't have any experience with ultra-low-power uCs and every vendor seems to have the most energy efficient one in the world.  uAs/MHz specs not-withstanding.

[ColinB]

EFM32 are great low power design, but Freescale Kinetis L KL25Z is possibly cheaper for about same power consumption and has good compatibility among all Kinetis chips.

[madshaman]

Thanks!  I'll take a look at the Kinetis too.

[dannyf]

I can make which takes almost no power

Then MSP430.

Other ARM chips would include the STM32L from ST.

[ColinB]

I also have compared Kinetis L with MSP430 and STM32(L).

I love the design of the MSP430 and it is a great chip, but (1) you will pay more to get 8KB+ RAM than on ARMs and (2) there is little pin compatibility between low end MSP430 chips and higher end ones, so you can't start out with a $1.00 value line chip in PDIP and then upgrade RAM beyond 512 bytes.

The STM32L is good, but until just recently when they announced the STM32L100 value line variant it was much more expensive than the Kinetis L options. Now it may be more competitive. I think Kinetis still has better package size choice, up to 80 LQFP than the STM32L100 but I will need to review my notes to check that.

[madshaman]

Thanks again for the pointers guys, I might dive in with two low power mcus.

[andyturk]

On the low power topic, the STM32L15x datasheet says the parts consume 214uA/MHz. I guess that passed for "ultra low power" a while back. But the new STM32F401 is way better at 137uA/MHz (if you can believe datasheets). That's in the realm of MSP430 power consumption.

[Andlier]

On the low power topic, the STM32L15x datasheet says the parts consume 214uA/MHz. I guess that passed for "ultra low power" a while back. But the new STM32F401 is way better at 137uA/MHz (if you can believe datasheets). That's in the realm of MSP430 power consumption.

As far as I can see in the datasheet, that number is achieved when running code from SRAM. Running from flash with prefetch enabled, consumes around 250uA/MHz, still ok for an M4. In full retention sleep mode it leaks like sieve though (10-100uA), and wake up takes ages (10-100us)...

[tjaeger]

The EFM32ZG looks really cool.  You can pick these up for a little over $1 at mouser right now.  Power consumption is going to be lower than the Kinetis (of course you can argue how much of a difference 3 µA vs 0.5/0.9 µA really makes) and seems to be on par with the MSP430 (while being of course much more powerful).  It has some interesting peripherals too: a 5-bit current DAC and what they call Peripheral Reflex System, which can respond to certain events without waking up the CPU.  It also comes with a UART bootloader. They have good application notes, which come with source code (through Simplicity Studio) including Makefiles for gcc-arm-embedded that almost work out-of-the box. I was really impressed by that.  I can't wait to play with mine once I figure out how to solder the pain-in-the-ass QFN package.

[dannyf]

Those were Energy micro's products, known for low power consumption (aka msp430 type of niches).

[madshaman]

The EFM32ZG looks really cool.  You can pick these up for a little over $1 at mouser right now.  Power consumption is going to be lower than the Kinetis (of course you can argue how much of a difference 3 µA vs 0.5/0.9 µA really makes) and seems to be on par with the MSP430 (while being of course much more powerful).  It has some interesting peripherals too: a 5-bit current DAC and what they call Peripheral Reflex System, which can respond to certain events without waking up the CPU.  It also comes with a UART bootloader. They have good application notes, which come with source code (through Simplicity Studio) including Makefiles for gcc-arm-embedded that almost work out-of-the box. I was really impressed by that.  I can't wait to play with mine once I figure out how to solder the pain-in-the-ass QFN package.

Yeah, I'm going with the EFM32ZG to poke my nose into this realm, it looked pretty awesome to me and based on others' opinions it'd definitely not a *bad* choice.

[tjaeger]

There are some annoying limitations you should be aware of, especially in the way signals are routed out (the good news is that it's easy to spot these problems with energyAware Designer):
* There are at most 4 ADC channels (the smallest parts only have two).  And to add insult to injury, if you want to use both a LF crystal and SPI, you lose two of those channels. 
* There is no low-frequency timer.  You can still get interrupts from the RTC when in low-energy mode, but no capture/compare.  I think it is technically possible to run the peripherals on a low-frequency clock, but that will force the core to run on the same clock.