MCU Selection for BLE and battery device - Page 1
Forum section: electronics / general

author: joeyjoejoe
author_rank: Frequent Contributor
timestamp: December 05, 2024, 09:36:36 pm
content: I'm looking to make a simple BLE button that will run off a single coin-cell or two AA's.I've done a lot of work with the ESP32, but the low-power modes are still pretty "bad". I suppose I could put in a self-latching circuit.nRF and STM come to mind - is there anything else I should be looking at?Thanks in advance!

author: SiliconWizard
author_rank: Super Contributor
timestamp: December 05, 2024, 10:27:03 pm
content: If your device only has a low duty cycle (like, it wakes up every few minutes), the ESP32 (at least C3 and C6, probably S3 as well) can still be used. Just use their standby mode, they draw as little as 5 µA in standby.Granted they're not as good as others in that the standby mode requires a full boot to wake up (which can last as long as about 500 ms), but if again it wakes up infrequently, that's still fine. If you were considering using an external power switch to power it down, then clearly you'd be in the same boat anyway. So no need for that. Just put them in standby. They can even retain some RAM in standby.If you want something that wakes up much faster and don't require a reboot, then yes, forget about them. There are tons of candidates these days. If you want something with integrated RF supporting BLE, then one of the lowest power of all is the Ambiq Apollo 3 Blue. It's not even expensive at all. You can also consider the nRF52 series as well, very good. OnSemi RSL10/15. The STM32L4/L5/U5 are very low power too and pretty good but don't come with integrated RF. There is the STM32WB series, with integrated RF, but I have no experience with those. They're probably a good fit too.

author: joeyjoejoe
author_rank: Frequent Contributor
timestamp: December 05, 2024, 10:55:50 pm
content: Thanks!Yeah the STM32WB looks cheap and good enough, and 8nA in shutdown, 1uA in "deepstop" mode. Has a nucleo board as well so I could play with it first before making a design.

author: SiliconWizard
author_rank: Super Contributor
timestamp: December 05, 2024, 10:59:29 pm
content: One benefit of the STM32 compared to the others I listed is indeed the availability of very cheap dev boards.

author: joeyjoejoe
author_rank: Frequent Contributor
timestamp: December 05, 2024, 10:59:59 pm
content: Figuring out their product lines is another thing

author: tszaboo
author_rank: Super Contributor
timestamp: December 06, 2024, 11:43:15 am
content: Quote from: YYIC on December 06, 2024, 10:21:26 amThank you totallynotchatgpt. Can you tell me how to make a cupcake ?

author: pcprogrammer
author_rank: Super Contributor
timestamp: December 06, 2024, 11:53:19 am
content: Quote from: tszaboo on December 06, 2024, 11:43:15 amMaybe a recipe for an egg roll. Not sure if cupcake's are common in China.Somebody is trying to sell their goods via this forum. At least they provided a long list with possible options for the OP to choose from.

author: tellurium
author_rank: Frequent Contributor
timestamp: December 06, 2024, 04:26:03 pm
content: Love ST's dev boards!Though their Nucleo boards have those long buttonsThose buttons always break, however ST is very consistent with using them all the time

author: joeyjoejoe
author_rank: Frequent Contributor
timestamp: December 06, 2024, 10:27:38 pm
content: Can I ignore the 32kHz crystal on STM32WB05xZ ? Data sheet says 32Mhz is a must, it uses the words "can" for 32kHz. I assume this is maybe for RTC or some sort of low power wakeup, but if I am just going to trigger my wakeup from a physical switch, perhaps I can skip?This will be my first STM design so a fun learning exercise.

author: tszaboo
author_rank: Super Contributor
timestamp: December 06, 2024, 11:45:24 pm
content: Design it in build the prototype with it. I you can write the code without it then leave it off the production boards.

author: SiliconWizard
author_rank: Super Contributor
timestamp: December 06, 2024, 11:57:32 pm
content: Quote from: joeyjoejoe on December 06, 2024, 10:27:38 pmA 32.768 kHz crystal for the LSE oscillator is always optional on all STM32's.But I thought you were going to buy a dev board? I really suggest testing what needs tested on it first and designing your own board afterwards.

author: Smokey
author_rank: Super Contributor
timestamp: December 07, 2024, 01:01:39 am
content: How many do you plan on making? If it's a volume product then you might want to make different choices than if you are making a couple widgets for yourself.

author: amyk
author_rank: Super Contributor
timestamp: December 07, 2024, 03:33:57 am
content: Take a look at JieLi's SoCs, if you can figure out how to use them they're ridiculously cheap and found in a ton of other BLE products.

author: joeyjoejoe
author_rank: Frequent Contributor
timestamp: December 07, 2024, 02:34:09 pm
content: Quote from: amyk on December 07, 2024, 03:33:57 amI had thought about trying to get into that game. But I'm unsure if it will be worth the hassle?Nucleo is in the shopping cart for sure to play around, the design happens in parallelDamn, the BOM count for the STM32WB is tiny if you want bare bones! Are all the STM's like this? It looks like VDD, some decoupling caps and a crystal and you're done! The SMPS is optional.

author: SiliconWizard
author_rank: Super Contributor
timestamp: December 07, 2024, 10:33:03 pm
content: Quote from: joeyjoejoe on December 07, 2024, 02:34:09 pmUnless you want to design something ultra tiny, just place the footprint for a 32k crystal and if it's of no use, just don't populate it.Yes, all STM32 only require a few bypass caps (number depending on the package) and even the crystal is often not required unless you have critical timings. (If it include a RF front-end, a crystal will almost always be required, but otherwise, not necessarily.) But that's the case for most other vendors as well?

author: betocool
author_rank: Regular Contributor
timestamp: December 09, 2024, 10:39:41 am
content: Hey, I've been using an NRF52 for a project lately, it works very well. Didn't get it into the lowest power modes, but that's beside the point, I didn't really try!Documentation and examples are pretty good, and the NRF forum is very supportive, unlike the STM32 one. Support tools for Android devices and bootloader are also pretty good.Downsides, the IDE is a bit hit and miss sometimes, and it uses Zephyr as its OS. I got used to it, but I try to avoid it. Too Linux-y for a microcontroller IMHO.Cheers,Alberto

author: joeyjoejoe
author_rank: Frequent Contributor
timestamp: December 09, 2024, 01:16:56 pm
content: Quote from: betocool on December 09, 2024, 10:39:41 amThat is too bad, but it does look like PlatformIO supports the NRF series to some degree at least so I could avoid that.

author: glenenglish
author_rank: Frequent Contributor
timestamp: December 26, 2024, 05:00:55 am
content: Suggest Rowley Associates IDE /debugger tools for STM32 if you want something decent and pro.https://www.rowley.co.uk/arm/index.htm

author: __george__
author_rank: Contributor
timestamp: December 26, 2024, 09:09:15 pm
content: Quote from: SiliconWizard on December 05, 2024, 10:27:03 pmThe dev board for the Ampiq Apollo 3 blue costs around 150 euros! I checked their SDK page and it ends up in their contact page. Do you need an NDA to use their SDK?

author: SiliconWizard
author_rank: Super Contributor
timestamp: December 26, 2024, 09:36:52 pm
content: Quote from: __george__ on December 26, 2024, 09:09:15 pmYou just need to create an account on their web site, at least that's what I did.https://contentportal.ambiq.com/loginDownload the AmbiqSuite SDK.Yes their dev boards are not cheap, but their MCUs themselves are pretty cheap OTOH. You can consider third-party boards - Sparkfun has a dev board that is pretty cheap:https://www.sparkfun.com/products/16828

author: __george__
author_rank: Contributor
timestamp: December 26, 2024, 10:27:18 pm
content: Glad to know that you don't need an NDA and for the suggestion, the sparkfun seems pretty good indeed

author: nimish
author_rank: Regular Contributor
timestamp: December 28, 2024, 12:17:59 am
content: RSl15 is decent for this. Exceptionally low sleep current. Has a module from murata too.