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How this is better than ESP8266?
This one is Bluetooth low-energy, ESP8266 is WiFi. Also the ESP8266 uses an obscure core (Xtensa LX106) whereas this one uses a Cortex M0. So most likely this one is much more energy efficient.
Yes, the Cortex M0 chip from Nordic can last years in a low-intensity Bluetooth connection. It can spend almost all it's time in the deep sleep modes and only read some sensor and connect to the phone to keep the connection alive every second or so.

It's a very different use-case than that of the ESP8266.

ESP8266 can the same, but Wifi.
WiFi needs way more power, so you can't run it long-term on batteries.
You most certainly can spurt WiFi for days and days .. and don't need to stay up.

I say this, because I have devices doing it in front of me. Maybe not for 'years and years', but certainly efficiently enough for long-term sensor usage.

"spurt"? (sorry, not a native speaker, can't make sense of the word in this context)

I guess it really depends on how often you have to transmit - if you have hourly checkins the world looks better than if you have to update something every minute or so.

I regularly open and close Wifi, send a 'spurt' of data, and shut down the Wifi. This is on a system with a 400mAH battery, it stays on for days and days without much fuss .. certainly BLTE and co. (where is ANT+ these days?) are lower-energy, but even if its only 'just close' in terms of energy efficiency, all the advantages of using Wifi instead of Bluetooth are huge.
Spurt: a short, sudden burst. A short spray of water from a garden hose could be a "spurt". We use the phrase "growth spurt" to describe when a child grows taller in a short time.

They're using it to describe a short, relatively large transfer of accumulated data collected while the wifi connection is deactivated, and transferred in a sudden stream when it's turned on.

How is a banana better than an apple? :) They are two different beasts, with two different stacks, and two different means of communication - all with completely different tradeoffs.

A Cortex-M0 + BLE setup would easily outlast an ESP8266 battery-wise, it would also make more sense on the go (BLE devices can communicate directly with a phone app, without much setup). While an ESP8266 is more general - can connect directly to wifi (more work, and more "stationary").

Do you know how both compare performance wise?
It's more how is a banana better than a chicken. Sure they're both food, but you're unlikely to have a situation where they're direct substitutes.
Apart from the fact that this is BLE and that is Wifi?

* Good English documentation * Radio is fully documented - you can make your own wireless protocols * Supported by mBed

This is nice, but aside from the breadboard-friendly package I'm not sure if it offers any advantage over all of the other nRF51822 modules that are available. Seeed offer one with the same SoC for $7.50, and it's not that hard to solder the package.

http://www.seeedstudio.com/depot/MDBT40P%C2%A0%C2%A0nRF51822...

Yes, in addition to that there is also:

* RFduino - has the advantage of being available on RS. Downsides: 16 kB version, no 32 kHz crystal, very few IO pins exposed.

* BMD-200 - 32 kB version, cheap if you're in the US, well made, 15 GPIOs exposed, no 32 kHz crystal

* Simblee (by same guys as RFduino) - 32 kB version, 32 kHz crystal, more GPIOs, tiny, quite expensive though

Nordic maintains a list of modules:

https://www.nordicsemi.com/Products/3rd-Party-Bluetooth-Smar...

Not to mention the teensy line. Unless you *really need the slightly smaller size, these things are great:

https://www.pjrc.com/teensy/

Just to be explicit, while this competes in the "tiny but breadboard-friendly microcontroller" market, it's not a nRF51 board (it's actually a more powerful chip, CPU-wise) and it does not have any sort of radio, bluetooth or otherwise.

The support from PJRC is great, though. And if you want to use the Arduino environment, I don't think anyone puts more work into making it work flawlessly on a non-AVR platform than Paul does, not even the Arduino guys themselves with their own ARM boards.

Yea this board in no way should cost $25, and is really late to the game with a nordic BLE board. Their website is really disingenuous about things that the Nordic BLE chip just has inside. http://oshchip.org/ Things like: "OSHChip_V1.0 is a unique combination of" (insert list of things inside the nrf51 series). How is it a unique combination of those things?? "You get to be a chip designer." Um, what how exactly do you get to be a chip designer?? You mean, you get to choose whether or not to use the I2C port that is built-in? Anyway, obviously they are marketing this toward students with that type of language. Which is great, good on them, but if it hits hacker news I think it deserves a bit of criticism if they list "professionals" as one of the people this applies to--especially with the price compared to other modules that have been around for some time.
And in the least elegant, but cheapest, form factor WaveShare make a module they call the Core51822[1] that is cloned by tons of folks and is basically the generic nrf51822 module you'll find for ~$5 on ebay. It's the most awkward compromise of 2mm pins (and in double rows too) that make it wholly incompatible with a breadboard yet it's also bigger than any other "embedded" module. But there's also a BLE400[2] "motherboard" which breaks the module's pins out to 2.54mm-spaced connectors, along with a few LEDs and buttons and a USB serial chip (all of which can be disconnected via jumpers), and one of those old, giant, 20-pin JTAG connectors.

It's not able to plug straight into a breadboard, but it does allow full access to every possible IO pin on the chip, and it's probably the cheapest setup you can find. A combination of a Core51822 and BLE400 seem to be easily available for ~$15-$20 shipped, there's even stock available through an Amazon Prime seller for $22.

If you do go for cheaper options, keep the chip differences in mind. The nRF51822 is currently available in three variants, and the differences are big. AA has 16K RAM and 128K Flash, AB has 16K RAM and 256K Flash, and the AC has 32K RAM and 256K Flash. The AC variant was only introduced recently, so some options might still have the older/cheaper variants. But some examples and tools (such as Nordic's BLE sniffer firmware and tools) are starting to require the latest chip with the 32K of RAM, so make sure whatever you're buying explicitly promises you'll get the 32K RAM chip (the AC variant), like this OSHChip does.

[1]: http://www.waveshare.com/wiki/Core51822

[2]: http://www.waveshare.com/wiki/BLE400

(related) OT: is there anything similar to this/ESP8266 with wired Ethernet (PoE would be awesome, but not necessary)?

There are a bunch of boards based on the WS5100, but that isn't that powerful and doesn't have great tooling, and then you quickly end up with "full" ARM boards like the raspberry, with size and price to match.

Full-sized boards and/or more expensive. The only one that looks really compact is 60-70 bucks.
It looks like the smallest of those WizNET W7500 boards is only $30[1], and includes a magjack on a carrier board (not shown in the mbed pictures) which is still fairly compact overall. The W7500 seems to include a Cortex-M0 that you can run your own code on, so it could be more interesting than the W5100 chips. I doubt it will end up being available in a $2 module, though.

[1]: http://www.shopwiznet.com/wizwiki-w7500econet

missed that one, thanks!
You may have a hard time finding great tooling AND a price lower than the Raspberry Pi. The MBED boards are very easy to use but are a little pricey. This board is an OpenWRT router chip (Ethernet and WiFi) for 15 Euros but you will have to rely on generic OpenWRT documentation:

https://www.olimex.com/Products/OLinuXino/RT5350F/

"Shipping to United Kingdom starts at $36.00 (£25.67 GBP)"

More than the product!

$8 to the US; I get books and CDs from the UK for $4 including S&H thought Amazon.com, granted, those outfits do it in bulk, but I wonder why it's so much more.

Tron-Club, which ships kits, packets of electronics and a manual once a month from Canada, will ship to the U.K. for £3.99, or £14.99 total vs. $19.99 to the US (http://tronclub.com/subscribe).

Tron club looks awesome, I just subscribed. Thanks for sharing this
You're very welcome. They make a few mistakes which they correct (on the forum and then ship with a subsequent kit), but they're otherwise totally awesome, just got my 7th kit.

Here's a prior HN discussion: https://news.ycombinator.com/item?id=9889777 and per my comment, they do indeed do a moderate amount of analog.

Can't even bother to localize to the US for shipping. someone isn't telling the whole story eh ?

call me when it's 0.49 to ship.

jrjr

That shipping rate also applies to Canada, so something is really messed up on their end. That's inexcusably high.
They're probably sending by DHL or something. They could send something that small by USPS for under $5.
Maybe 20 years ago. USPS isn't sending anything in a box to the UK for less than $20 (delivered in 2-3 weeks.. unless you want to pay double for priority).
This is a tiny module. It'll go in an envelope.
Well if that envelope is more than 3/4inch thick or has more than 1/4in variation or more than 2 inches of movement inside the envelope or cannot bend at least 1 in (because it contains a rigid object for example)

Then guess what? It qualifies as a package and not an envelope and you must pay the same price as a box

So again.. $20

If they're sending lots of these it can easily be worked-around. But yes, US postage is ridiculous. I've fulfilled packages that weren't time-sensitive directly from Hong Kong to the US as amazingly it was cheaper than sending domestically from a US warehouse.

I can send a 100g "large letter" from the UK to US for about £3 (about $5), and the only size restriction is that it must fit through a 2.5cm by 25cm slot, and can't be longer than 35cm. No bending or shape restrictions. For an extra £1 I can send a small parcel, which has even looser restrictions. The main problem is that over 2kg the prices jump massively.

These costs are all for 5-7 day delivery.

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