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Comment by janjongboom | Hacker News Reader

Why are we even using a Raspberry Pi for battery powered projects... 30 mA draw is so high you'll be changing batteries every 2 days, and that is without doing anything. Compare that to f.e. a normal phone chipset with deep sleep, which draws about 9 mA with a cellular connection, or .1-.2 mA in flight mode.

Or, if you just use the Pi for sensor readings, get a proper microcontroller, where current is measured in micro (or even nano-)amps...

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For someone like me who has only just started playing with microcontrollers thanks to the Arduino and RasPi and has never touched/played with anything else.. could you give any suggestions/links on what I should consider using for sensors?

I have a bunch of "nodes" I need to make, each one has a single sensor (temperature, moisture, light, or distance using a sonic sensor) that will send back to a Raspberry Pi base station. I was going to use RasPi's for all of them since it's all I know. Each will be battery powered with a solar panel. Open to any/all suggestions people can give me on how best to attack this!

Esp8266 wifi/micro module. You can program it in lua!

Yeah, ESP8266 is a good choice for IoT projects. It supports quite a few different languages, I think the most recent addition was BASIC. It's very cheap as well (have seen people talking about prices as low as $3).

http://www.esp8266.com

Also worth knowing that the successor to the ESP8266, the ESP32, is currently in beta testing:

https://hackaday.com/2015/11/06/the-latest-best-wifi-module-...

https://twitter.com/hashtag/esp32

You can order them for about US$3 per unit, or $2.85 if you order 10 from BangGood.[1]

You can get them for even cheaper directly from Chinese distributors.

Banggood, DealExtreme and AlieExpress are convenient and ship worldwide, but they are not the cheapest, although they are usually already quite cheap compared to most.

[1]:http://www.banggood.com/ESP8266-ESP-12E-Remote-Serial-Port-W...

Depends on how they communicate between each other. I'm doing some stuff around LoRa [1] for long range communication, and my base station is a Rpi, the end nodes can be any type of microcontroller. E.g. [2] which comes with ARM's mbed, which even allows me to program them from the browser. For Bluetooth pick anything based on nrf58122, e.g. [3]. For WiFi pick ESP 8266 [4].

[1] http://www.link-labs.com/what-is-lora/ [2] http://www.multitech.com/brands/multiconnect-mdot [3] https://www.nordicsemi.com/eng/Products/Bluetooth-Smart-Blue... [4] http://www.espruino.com/ESP8266

In general the mbed has the better options for low power , but if you prefer the arduino, this would be a good starting point:

http://jeelabs.org/tag/lowpower/

And if you want a long-range, low-power wireless connection - use LoRa , There's a driver here:

http://www.airspayce.com/mikem/arduino/RadioHead/classRH__RF...

How have you found the mbed OS tools/community/documentation to be? I've played around a bit with Arduino but I'm interested in checking mbed out.

In general Arduino definitely leads in documentation. The mbed community is smaller , but on the other hand more professional - so stuff would be of higher quality , less bugs , etc - but somewhat more complicated. Same goes for the tools - more complicated but more capable. If you're aiming towards something professional/startup/etc - mbed is the way .

Teensy is awesome, cheaper than Arduino and many times more powerful

http://pjrc.com/teensy/index.html

If you need something that has clock speed in the hundreds of MHz and RAM in the hundreds of MBs then the Arietta G25 is maybe a good option - http://www.acmesystems.it/arietta.

Until this current wave of boards (CHIP, RPi zero) it was pretty much on its own in the land of dev boards - substantially beefier than Arduino, ESP8266 and Teensy 3.2 but way leaner than the RPi and BBB et al.

I still think it's a nice piece of kit even in the context of these new ARM boards.

Update: found some numbers on current draw - looks like out of the box it sits around 40mA idle, so slightly more than they tweaked the RPi Zero down to. http://www.robertoasquini.com/?p=148

Looks really nice. How do you find the low-level peripheral stuff? Past experiences have taught me to trust Atmel's data sheets and examples way more than the ST or NXP ones, but that's been on simpler chips/projects, so I don't know if it carries over to here.

Also, is there an easy way to have an isolated realtime component, eg closed loop controller for motor drive? Could you just set up a hardware timer interrupt that preempts the kernel?

The MSP430 is renowned for low power and will idle (i.e. suspended waiting for interrupts) at microamps.

Architecturally it's a 16 bit Von Neumann architecture at up to 16MHz with a remarkably elegant ISA and extensions to let it address more memory. Most interestingly, some devices have 64kB or 128kB of FRAM --- non-volatile RAM which operates at SRAM speeds! And because it's a Von Neumann architecture you can load programs off disk into it, which lets you do some cool stuff. (I ported Alan Cox's Fuzix to one.) Of course, an SD card will use loads more RAM than the CPU itself.

I believe you can run one with no external components whatsoever. Hook it up to 0V and 3.3V and it'll run at 8MHzish on its internal oscillator.

Another argument for MSP430 as a replacement for arduino and such is that even the smallest devices support reasonable debugger.

As for external devices: at least G-series need external components to generate reset pulse to reliably boot (it mostly works with reset left floating, but whether it reliably works is function of how quickly the power ramps up, I got burned by this on last project).

Regarding debugging: I don't know what additional hardware you need to debug MSP430, but there's Atmel's AVR "debugWire" which works ok with gdb.

http://www.larsen-b.com/Article/315.html

I used it with a AVR Dragon (a rather full-featured, but still relatively inexpensive AVR programmer). You can use it with Arduino boards, of course, when you solder in the 6-pin ISP socket. (e.g. the pin header on the right of https://www.arduino.cc/en/Main/ArduinoBoardUno )

http://www.atmel.com/tools/AVRDRAGON.aspx

There are good answers already, here is my suggestion : once you are confortable with Arduino, look into using just the microcontroller (for example the ATMega328p of the Uno), and solder it on a protoboard with your sensors. You use the exact same code, you can easily load it via an Arduino (beware, you need an Arduino with a DIP microcontroller you can remove). Look up "Bareduino", that's the spirit.

Then you can have a look to smaller microcontroller (if your project allows it), for example the ATTiny family. You can get to ~10/20uA consumption when using deep sleep and only reading sensors once a while.

The most useful thing to have when working with embedded electronics is to have in-circuit programmers. Please don't get into the habit of swapping parts between, e.g., the Arduino board and your own... It's getting very tedious, very fast.

The simplest programmers (ISP: In System Programmer) are only a few dollars, and they allow you to burn your creations in blank off-the-factory chips without bootloader. I think there's even an Arduino project that turns your arduino into a (very limited) STK500 compatible programmer...

[a quick web search turns up https://www.arduino.cc/en/Tutorial/ArduinoISP ]

The Pi (and Arduino) is a gateway drug, imo. As a software guy, I don't think I'd have ever gotten into circuit design or hardware hacking of any sort until I brought a Pi B and Arduino Uno.

For fun, first-time projects, it's a lot easier to have someone write a Python script and go, rather than breadboard a circuit and write in a more obscure, less-abstracted language.

check out http://wipy.io/ . Best of both worlds and draws 850uA in suspend mode.

Cool! I did not realize there was a board with built-in wifi that ran https://micropython.org/

Very cool; unfortunately it's a bit pricey... and won't be available for a while. I'd like to pick one up when it is, though!

At this rate it's not far off what you would get with an ATtiny while active, which consumes around 10mA[0], the difference is that those and other micro controllers have sleep modes which reduce the consumption into the uA range - hopefully details on something like that for the Pi will be released too.

[0] https://learn.sparkfun.com/tutorials/h2ohno/low-power-attiny

But are these phone chip application-class or domain specific ones ? meaning you can leverage linux ecosystem or do you have to program on their ~OS ?

I was looking for the most power efficient thing that could run a minimal desktop on battery and fit into my palm.

Kinda unrelated to the whole Rpi discussion, but the SOC of any phone that runs Android would do. If that is Linux'y enough for you then it could be a solution. The problem is sourcing the SOCs. Spreadtrum makes some nice chips that include app processor, cellular, WiFi, Bluetooth, etc. for ~7$ but they're not for sale if you're not an ODM.

This is a great article [1] about how Chinese SOC manufacturers and Chinese IP works. I ended up just ripping out the mainboard of phones to get access to the SOC [2].

[1] http://www.bunniestudios.com/blog/?p=4297 [2] http://janos.io/

I thougth you were thinking of ~dumbphones, but sure enough any smartphone these days is exceptional in most features. Just today I saw a chinese dual core smartphone phone for 34$... The thing is that unless you're already in the know you can't repurpose the board.

ps: funny, just an hour ago I was trying to flash an old nexus s with CM*.

> "The thing is that unless you're already in the know you can't repurpose the board."

That's why projects like Fernvale are potentially very useful, as they would make it easier to repurpose the cheap hardware used for feature phones:

https://www.youtube.com/watch?v=hpEqDPYtf9s

https://github.com/xobs/fernly

I heard Bunnie was a master but the FPGA cpu MITM had me sitting down. Fantasy level impressive.

On the higher end you have last gen quad core Intel Atom Tablets with Windows 10, 2gb ram, USB, bluetooth, wifi and 8'' touch screen for 80$ [1].

The price of hardware in China is beyond amazing - honestly I could run a laptop off those specs with a slightly larger better screen (assuming I don't need to compile C++ :D)

[1] http://www.banggood.com/Cube-iWork8-Ultimate-32GB-Intel-Cher...

And even compiling C++... synthetically this thing is 50% faster than my current laptop. In 2008 this would have been a great machine to program in C++.

First and foremost, the Raspi boards are for teaching. That's the goal of the foundation. I would guess the vast majority of people who buy a raspi are dipping their toes in to the world of hardware - not building semi/permanent applications.

Yes there are absolutely better suited platforms.

That's what people who don't own smartphones say about smartphones.

Smartphones last as long as dumb phones if you turn off background data transfers.

So it spends part of the time being highly capable, and part of the time sleeping with no downsides.

The Pi is just not cut out to be a passive battery-powered device.

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