NRF52840 Connect Kit – Rapid prototyping kit for your next connected projects
github.com
github.com
Personally I've found that for casual experimenting and software development, the official nRF52840 DK board is your best bet. Here in the US it only costs around $50, and all of the samples in the nRF Connect SDK support it natively. It's also pre-wired for power measurement.
My first board was the nRF52840 MDK from makerdiary. I ordered it from Amazon because it was cheap and it had one-day delivery. Most of the NCS samples do not support the makerdiary boards as-is. You can usually add a dts .overlay file to the sample to get it working, but it will take a bit of extra effort. Having to tweak device trees right off the bat adds another step to the learning curve and makes it harder to try out random sample apps.
Over time I migrated to using the DK for development (the integrated debugger + serial interfaces are super handy) and then using the USD $10 nRF52840 Dongle boards for deployment. I program the dongle boards using a knockoff J-Link probe from Aliexpress and run them off battery power. I eventually stopped using the makerdiary MDK since it didn't really fill a niche for me. But YMMV.
One nice thing about the board in this article is that it has an external SPI flash, which could be useful if the nRF52840's 1MB onchip flash isn't large enough for your application. I use A/B partitions to support OTA updates and it's pretty easy to run over 512kB per image if your use case is moderately complex.
One of the main factors driving me back to the DK board was the fact that many NCS samples take advantage of the 4 switches + 4 LEDs on the DK board. Even the light_switch sample uses all 4 buttons to trigger different functionality.
The smaller boards don't have room for these switches and LEDs, so you'd have to tweak the program to work around the hardware differences. And that's a big investment if you just wanted to play around with the stock sample code for a few minutes.
A more general critique of the NCS samples is that many of them require a great deal of "polishing" before you can use them in a real project. It would actually be helpful if NCS shipped ready-made overlays that allowed them to run on smaller boards like the MDK and Dongle, in a configuration that's closer to what a shippable product would look like. As it stands, a company that wants to ship a Zigbee bulb or switch has to do a lot of work to convert the samples into something usable.
Maybe this is worth filing some PRs on the sdk-nrf github.
Is there an advantage of using the NRF boards over ESP ones for home automation?
NRF52840 is specified to use 1.5uA when deep sleeping with RTC wake-up, while esp32-c3 is 5uA, which sounds ok, but is not the whole story.
If you try to build something low-power with ESP32 you'll find that it takes a lot of time and energy to go from deep sleep to being able to transmit, while the NRF SDK is designed with that in mind.
The NRF current consumption also includes the built-in voltage regulators -- this works from 1.7v to 5.5v, with a regulated output for peripherals, so all it needs is a battery and some passives.
On the other hand the ESP32 is much more awkward -- it needs 3-3.6v, so you're going to need an external regulator, and a LDO with the required 500mA output current is going to have a significant quiescent current, and even then the voltages are awkward for lithium batteries once you consider the drop-out voltage.
The tl;dr is that it's easy to get multiple years out of a coin cell with an NRF-based sensor, and that's just not happening with any ESP32.
Cheap Chargers are hard wired to deliver up to 2A.
As long as CP2102 can handle it, it's fine, but you can get a 500mA charger.
The non-RISCV ESP's are a very wonky architecture, and while there is lots of ESP code out there, finding stuff that just works is harder than one may think. Meanwhile, pretty much all NRF52840 stuff you will run into just works, and works reliably.
The toolchains and underlying pieces are also basically only supported by EspressIf (yes some work is upstream, but unlike ARM Cortex, you won't find a lot of help from others on Xtensa).
Real debugging of NRF52840 stuff is also easier to do because of this - lots and lots of debug tools work.
You will also get much better documentation out of Nordic.
Now, this is mostly about Xtensa, and almost certainly one of the reasons that they are moving the ESP's toward RISC-V.
I don't have enough experience with the newer RISC-V ones to give you a view there.
I thought the ESP3-S3 with USB integrated serial+soft JTAG adapter would be a big step forward
well turns out the situation with openocd/gdb/flaky USB stack/resetting issues after upload is IMO untenable
if you have a lot of time on your hands, every now and then debugging might work
Some of the newer ESP32 boards do support Zigbee but I don't think they were available yet when I started my project. Might be worth looking into ESP32-C6 now.
As others have mentioned, power consumption is also a consideration. My battery powered devices consume about 25uA and should theoretically last 5+ years on two lithium AAA cells.
"only"
One could buy at least like a dozen ESP32 boards for that price and probably get better support as well.
I think the greater hardware community is sleeping on Nordic right now, tbh. I know innovation does not happen super fast but when you compare this to a similarly priced STM32 that does objectively less, it’s no contest for me.
I tinker with embedded on Rust, and I spend more time on ESP32s than on the various nRF52s that I have. I only saw MakerDiary's boards recently, I hope that this can change.
As an aside, hobbyist programming in a language/platform that isn't well supported has the side effect that you end up spending more time growing trees instead of chopping them for wood.
There is more there in theory. But it's definitely treading on fresh snow in most places.
In that sense, using embassy with the NRF52840 was much easier to keep working vs either bare metal ESP32 rust or ESP-IDF based ESP32 rust. It's also debuggable. Good luck on the esp32, which is hard to debug even in C++.
Also, rust 52840 bluetooth is rock solid because it's soft-device based.
IC Mhz Coremark CM/Mhz
ESP8266 80 191 2.375
ESP32 (2 cores) 160 665.9 4.16
240 999.2 4.16
nRF52840 64 212 3.3
https://infocenter.nordicsemi.com/index.jsp?topic=%2Fps_nrf5...
Simply having ESP32 radio stack powered, not even transmitting, means a continuous additional (on top of everything else) power draw of 40~50mA. That is A LOT.
Which is 514 coremark for the application CPU (4CM/mhz) and 244 coremark for the network core (4CM/mhz).
Also, if you do it on a CM/milliamp basis, the NRF blows the ESP out of the water.
The network core is like 101CM per milliamp.
Turning on anything related to networking on the ESP32 adds 40-50ma vs 4ma on the NRF5340.
The NRF also has a real FPU, and accelerates more crypto than the ESP32 (and in a more standard way).
It is highly unlikely you will need more than the 5340 for home automation.
On a 5340, you would mostly run stuff on the lower power network core, and use the high power app core for "real" work. That works really well, and is easy to make work.
On the ESP32, trying to clock the cores differently is hard, and trying to use dual core at all on anything other than ESP-IDF is ... an exercise in frustration. So you spend a lot of time trying to make it sleep, which is ... also hard to get right (IE in a way that actually reduces power meaningfully)
Don't get me wrong - i do recommend ESP32's to people who just want to mess around with arduino libraries and don't care much about power or longevity.
But if you are trying to something serious, i'd pick the 52840 or the 5340 every day of the week.
https://en.wikipedia.org/wiki/Thread_(network_protocol)
Here's Thread vs Zigbee:
https://www.rfwireless-world.com/Terminology/Difference-betw...
Zigbee suffers from some of this but the protocol is much lighter and payloads smaller, which means the MCU can spend more CPU time and energy decoding messages. If we can get a chip that combines cellular with Bluetooth and LoRa, that would be a killer IoT platform.
The mesh network stuff was cool but suffered from a strange internal product decisions that made it useless for most applications.
First off, it was not created with a specific customer in mind. Most customers using IoT platforms want cellular connectivity, to allow for zero-setup on the customer or installer-side, and the ability to push OTA firmware updates. Mesh also used a Thread which was not super useful at the time. The vision was that you would be able to have a local network with one or more redundant gateways that ingress and egress of data through a few links.
This created another problem: monetization. In the gen 2 era of Particle where most customers with significant spend connected via cell network, Particle were able to charge a high margin rate and get considerable revenue as a result of their mvno business. This promise of a mesh network, where you could potentially reduce the number of internet connected devices to 10% of your original allocation, required rethinking of pricing as to capitalize on the devices that were connected to the mesh network but not acting as a gateway. What they did next destroyed any chance at widespread adoption. They created the most convoluted pricing systems where they were directly charging fees for a mesh connected device to be connected at all, as well as per network. Particle, whose OTA product famously worked extremely well coupled with a generous free tier (for device management) and that was easy to understand, decided to go generally available with a crippled mesh product, no customers for it, and extremely hard-to-understand pricing. Developers originally flocked to them because they could be certain of the service and features of each tier and that it just worked very well, but they destroyed trust with developers who were the genesis of most of their inbound leads.
What they should have done was to launch the products with a mesh communication library and charged for the gateways, using one pricing model if it was a stand-alone device and an upgraded one that would allow it to route mesh traffic through the internet. Oh, they also should have fucking gone with LoRa just like everyone was asking because 2.4Ghz at its tiny power is just outside of range of anything actually useful for the customers who actually wanted mesh networks
There is space another mesh product that is sanely designed and priced reasonably. I can’t see it coming from Particle, however. If anyone wants to start this, hit me up - my contact info is in my profile.
Wifi in particularly is a huge power hog and isn't really usable in low-power situations.
Surprised to see another nRF52840 product with a whole new repo for it. What parts of that repo can I also use on their MDK and what not, and why?
To give you an impression about how much trouble that was: I also bought a few dedicated general purpose programmer boards (cheap maker stuff), but in the end the arduino approach felt more accessible. Iirc the difference was that the purpose-built boards had more assumptions about what exactly they'd be used for baked into their documentation and I don't know enough about all that stuff to see through them