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The Raspberry Pi Zero

Pi Zero overview
As of 1 March 2017, the 'Zero W' launched. For the extra WiFi and Bluetooth functionality, you pay exactly twice as much == and guess what ??? no-one has the basic £4.80 Zero 'in stock' anymore, only the £9.60 Zero-W (in both cases, you have to add 2.50 P&P, and no, you can't combine both a Zero and a Zero-W into one order). So, does this mark the death knell of the '$5 game changer' ??? If so, it will be a real shame ...

The $5 (£4) Pi Zero, a DIY Project 'game changer'

The Pi Zero launched 25th November 2015 at a 'headline' retail price of £4 (which included VAT = since increased to £4.80) = about the same price as the recommended power supply. The first batch of 20,000 instantly sold out. For the next 6 months, any Pi Zero's reaching the distributors continued to sell out within minutes, even when some distributors took to selling 'bundle kits' of over-priced SDHC cards (pre-programmed with the NOOBS system) and exorbitantly priced 'cables sets'.

A few months after the launch the Pi Foundation released 'version 1.3' (with a micro-camera port socket, which, of course, allowed the distributors to sell yet another adaptor cable (needed to adapt the standard Pi Camera to the Pi Zero micro-port) at the same price as the Zero - and this was well before most people managed to obtain 'v 1.0' !

It was not until end of July 2016, well over 6 months since initial launch, that stock finally stopped selling out within 24 hrs of reaching the distributors. Although both UK distributors were still restricting orders to 'one per customer' (which meant the ACTUAL price was £6.50 i.e. £4 + £2.50 postage) by August 2016 it was possible to buy a Zero more or less whenever you wanted.

However with the launch of the Zero-W (end Feb 2017) at double the price of the original - all that changed yet again. Yes, the 'old' (v1.3) Pi Zero was back to being an almost instant sell-out. No doubt this was because, like me, the average hobbyist suspected that the now rather 'too cheap' Zero was about to be dropped in favour of the twice as expensive Zero-W.

On the other hand, by April 2017 you could get the Pi Zero to Pi-Camera cable for as little as £1.28 (post-free, eBay China = look for "Camera FFC Cable for Raspberry Pi Zero V1.3"), although the UK distributors are still charging £4 (and UK sellers on eBay charging even more).

As is normal with todays 'Chinese copy', the eBay version is actually a better design  than the 'official version' (which is a wide cable to the narrow Pi Zero connector, whilst the 'Chinese copy' is a narrow cable to the wide Pi-Camera connector = which means it uses up a lot less space)

Even at £6.50 the Pi Zero is still about 1/3rd the price of the A+, or (after adding a USB/Ethernet hub) about 1/3rd the price of the B+, making both '+' versions very poor value compared to the Zero (in fact, the only reason to pay 3x the price is if you really need the touch-screen Display connector). With the Pi B2 no longer manufactured, it's only the £32 quad-core B3 that can beat the Zero on performance (but not on price-performance, since for that price you can get almost 5 Pi Zeros :-) )

Nothing better illustrates the abysmal state of the UK Manufacturing industry than the Pi Zero shortages - whilst the Pi foundation continues to twiddle their thumbs (despite the obvious 'million plus' market demand staring them in the face) and with Pi Zero's being restricted to 'one per customer', you could purchase 'unlimited' quantities (actually, only just over 6,000 were on offer when I checked) of the 'Chinese copy' Pi - the 'Orange Pi One' - from Aliexpress at $10 each (postage included). Further, the 'Orange' Pi is claimed to be 'equivalent' to a Pi B2 but costs only slightly more than the 'one per customer postage extra' Pi Zero

Note that whilst the 'Chinese copy' Orange Pi line might have processing capability on par with the Pi 2/3, you need to watch out for connection differences - specifically the GPIO pins and display/camera header sockets - which are NOT 'Pi compatible' and (of course) every software package that uses the GPU in any way (it has a totally different GPU) - even getting audio out can be an exercise in futility, let alone getting any graphics to run (and that includes any 'windows' style GUI)
However, for projects where you don't need a fancy GUI, audio or either the Pi Camera or Pi Display - and are prepared to delve into I/O access differences, then, when you can't get hold of a Zero anyway, the Orange Pi may be a cheap alternative

The Pi Zero is a 'game changer' for the DIY project builder. It's small size and low cost makes it even better than the Pi A+, so demand is going to remain astronomical for some time. In the meantime, the BBC micro:bit ('competition' to the Pi Zero = or perhaps not) has finally started to be delivered. With a basic price of £13 (or upward of £30 with the usual rip-off cable 'kit') it's almost in the same price bracket as the Pi A+, but now looks totally overpriced (whilst being ludicrously 'under powered') compared to the Pi Zero.

The BBC at least have enough faith in their product to 'launch with a million' (apparently shipping to 'more than a million kids' started end of Mar 2016, after being twice delayed). However it's so underpowered (a joke 16 MHz ARM Cortex-M0 micro-controller, 256 KB Flash, 16 KB RAM), with no Operating System (just a 'bootstrap' that lets you download MicroPython 'scripts') that it's almost irrelevant to the serious hobbyist. In fact, the micro:Bit is rather reminiscent of the 20 year old 'Basic Stamp' PIC :-)

The price (and power) of the Pi Zero would also make it a 'game changer' for the DIY programmable controller chip application Project == but if only we could get hold of them !

The Pi Zero is about the same cost as a 32bit ATMEGA (the chip on the Arduino board) or Microchip 32bit series PIC processor, but delivers orders of magnitude more processing power (Pi Zero 1GHz CPU + 24 GFLOPS GPU v's about 100MHz for the ATmega / PIC).
Further, all Programmable chips lack RAM (about the max. RAM you can get 'on board' a PIC is 64kb, whilst the Pi Zero has 512Mb RAM (i.e. some 8,000x more) and program space (again, the PIC max is about 64kb, whilst the Pi has effectively no program space limit at all = you can even use a 128Gb SDHC card if you wish).
This means Project design compromises imposed by the ATmega or PIC CPU will no longer be a problem with the Pi Zero. In short, the PI Zero (if it ever becomes generally available in more than '1 per order' quantities) 'wipes out' the 'high end programmable chip' market at a stroke by some orders of magnitude.
The lower priced (sub-50p) programmable (PIC type) chips still have one main 'advantage' over the Pi (other than price) and that's their ability to run from 3v to about 6v with a very low power consumption i.e straight off batteries. So the low-end PIC 16Fxxx and 18Fxxx chips can still 'wipe the Pi' in many low-end niche application areas.

Finally it's hard to see why anyone would waste their money on the A+ or B+, as the Pi Zero with an micro-USB Ethernet + 3 port hub comes in at less than 1/2 the price of the A+ (and 1/3rd that of the B+)

It's to be noted that many distributors will try to sell you 'adapter kits', however you are always better off purchasing peripherals with the 'correct' plug (an adapter just reduces reliability by adding an extra connection to go wrong)
So, for example, instead of buying an "Ethernet + 3 USB" hub for your Pi Zero (which has the 'wrong' plug and is overpriced at £10) from a UK distributor, I suggest you go find the same thing with a micro-USB plug (for about 1/3rd the price) on eBay (ideally get one based on the Realtek RTL8152 chip set, which is known to work fine with the Pi).
The same applies to the HDMI connector. Rather than use a 'mini-HDMI to HDMI adapter' with a standard full-sized HDMI-HDMI cable get a 'mini-HDMI to standard HDMI cable' (or 'mini-HDMI to VGA converter') on eBay for half the UK price and aviod the space wasting and reliability reducing mini-full HDMI adapter.
Of course there are some things you can't get elsewhere (such as the pHAT DAC (£12) for audio out and (initialy) the Pi Zero camera cable (for a rip-off £4) - although these can now be found on ebay for £1.28 ea.)

Pi Zero system software

You need Raspbian 'Jessie' or 'NOOBS zero' - both are available as a 'zip' download from the Pi Foundation (be aware that even the 'basic' Jessie Lite 300Mb zip expands to about 1Gb) as Raspbian 'Wheezy' does not support the Zero.

NOOBS is a popular build that offers the user the choice of multiple 'Operating System builds' on first 'power up'. The drawback is that only Raspbian Jessie is actually included in the NOOBS package - if you choose one of the other 'builds' on offer (such as the Multimedia Player focused option), the Pi has to connect to the Internet to download up to a GigaByte of additional components.
This means you have to provide a 'path' to the Internet (unless you stick to Raspbian) = and that more or less means a USB Ethernet adapter wired to your LAN
In theory, once you have the Pi Zero emulating a 'USB device' you can plug it straight into your PC (using an OTG cable = see my Using the Pi Zero as a USB device page) and then use Windows ICS (Internet Connection Sharing) to provide a path for the Zero to the Internet. On the other hand, 'wget' has never worked for me across ICS
NB. At the time of writing (2016) even the 'full fat' Jessie system runs just fine on a basic 'class 4' 4Gb mini-SDHC card. These can be found for as little as £1 on eBay. Only users wanting to build a 'photo-frame' or a 'movie player' with 'on Pi' media files need use anything bigger (which makes the NOOBS pre-programmed 16Gb SDHC cards offered by UK Pi distributors an even bitter rip-off :-) )

Pi Zero connectors

Power (micro-USB) Like the others, the Pi Zero comes with the all but useless micro-USB socket for power connection, however (unlike the others) there are no 'reverse protection diodes' on either the 'power' or 'data' micro-USB connectors.

Further, the 40pin i/o header strip '5v pins' are also wired direct to the USB power pins - and the header strip is not 'populated', so you can solder direct to the holes !

This mean you are 'spoilt for choice' when it comes to powering the Pi Zero = you can use the 'power' micro-USB socket, 'back-drive' the Pi from the data-USB socket or just solder your power input wires direct to the 0.1" header holes (which you will have to do anyway, when, as usual, the power plug starts falling out of the micro-USB socket under the weight of it's own cable)

Note that the Pi Zero only actually needs 5v for the USB output socket (and 5v i/o header pins for external devices). If you don't heed to use the on-board USB, then IN THEORY you can run the entire Pi Zero on 3v3 !
You will need to bypass the 5v to 3v3 reg (RG2, NCP1117-3v3), lift pin 3 (the 3v3 output) and wire the Pi circuit board pad to your own 3v3 supply

(micro)-USB data Like the A/A+, the Zero has a single USB data connection, but on the Pi Zero this is a second micro-USB socket (and yes, that is a 'newbie confusion trap' = see later).

Some distributors are selling 'cable kits' with a 'micro to full USB converter/adapter' which risks damage to the micro-USB socket due to it's weight alone.
You should avoid all such 'cable kits' like the over-priced rip-offs they are. Instead, if you can't find a micro-USB version of the USB 'dongle' (or want to use the Zero with standard USB memory sticks), I recommend using an 'OTG extender cable' (which consists of a micro-USB plug to standard USB socket).
Of course many of your projects will require more than one USB socket, in which case a better choice is a micro-USB cabled powered hub (from which you can 'back drive' the Pi)
Note that the Zero can be used as a 'USB device' (by loading new USB pin 'definitions' - the USB pins are wired direct to the SoC so can be reprogrammed to operate in USB device mode) and powered from whatever it's plugged into !
As there are no 'reverse protection diodes' on either micro-USB connector, you can power the Zero from either socket. Whilst that makes 'back driving' easy, this is going to really confuse the 'newbie' (if you mix up the two sockets, the Zero will power up from the USB socket just fine, but no USB device plugged into the power socket will ever be 'recognised' :-) )

(mini)-HDMI Oddly, the Pi Zero is equipped with a mini-HDMI socket rather than the micro-HDMI version found on many Tablets (although it is very easy to confuse a micro-HDMI with the micro-USB socket - and trying to force a cable into the wrong socket will destroy them all too easily - so perhaps the Pi guys actually thought about this possibility and (finally) got something right).

Again, you should avoid the distributors rip-off 'cable kit' with it's mini-to-full to HDMI 'converter' which then means using a 'standard' HDMI cable = for sure the combined weight of a 'converter' plus HDMI cable will damage the mini-HDMI socket.
Instead I recommend you go for a 'mini-HDMI to standard HDMI' cable (or, if your application uses an old SVGA display, a 'mini-HDMI to VGA converter').

On the subject of mini-HDMI-VGA converter, if there is sufficient space around your displays VGA socket to 'mount' the converter, the 'best' way to connect the converter to the display is with a '15pin VGA gender changer' (pins to pins), rather that with a (cheap) 1m VGA cable (or expensive 0.5m cable). At £1 or less, the 'gender changer' is about the same cost as a 1m VGA cable but it uses a lot less space (and provides a neater solution)

If you must have a standard HDMI socket at the Pi Zero (for example, so you can 'develop' using a B series Pi and then 'swap out' for the Zero later) you need to 'box' the Zero in a way that allows the mini-HDMI to standard HDMI adapter to be supported by the box (and not the Pi Zero socket)

(micro)-SDHC Like the A/B+ and B2, the Pi Zero is equipped with a micro-SDHC socket for it's 'program' store. A cheap 4Gb micro-SDHC can be had for £1, however you will need a PC to download one of the Pi operating systems and 'burn' it to the chip

The Pi foundation has taken to 'bundling' about 1Gb of extra 'stuff' (LibreOffice and Wolfram) into the NOOBS distro. as part of Raspbian (the only 'full' Operating System included in the 'NOOBS' package - if you choose one of the other O/S's at NOOBS launch, the Pi has to go off and start downloading Mb's of stuff).
This means you really need a 8Gb SDHC chip (still only about £2 from China, or a lot more when 'bundled' with a Pi).
It's easy enough to remove the unwanted stuffing to make space later (sudo apt-get remove --purge libreoffice-*, sudo apt-get remove --purge wolfram-engine). You can even cut down Raspbian itself = see here

The 40pin 0.1" i/o header Rather than the bare 0.1" pins, the Pi zero just has holes in the PCB == so at last you can fit a 0.1" header SOCKET (and protect the GPU i/o pins from accidental shorting or from blowing the GPU (by brushing against the pins causing a static discharge)

Pi Zero box
The Pi Zero 40pin header (left)
(for more details, see here)

Fitting a socket makes it a LOT SIMPLER to use the Pi Zero when 'prototyping'. Specifically, a socket means you can use standard 'bread boarding' pin-to-pin jumper wires (rather than having to buy special pin-to-socket jumpers at the usual Pi distributor rip-off prices)

Most project builders will solder direct to the holes - after all, why add yet another connector that can only add to the chances of your system failing ?
If you must use pins, strips of 20-50 pins can be had for pennies from eBay (rather than pennies per pin from the UK distributors). To avoid lots of soldering, you can 'break off' just those few pins you actually need. 

What can't the Pi Zero do ?

It can't be run (directly) from batteries. Like any other Pi, you can't just plug the Zero into a '6v' battery pack and expect it to work.

All Pi's require 5.0v (+/- about 0.25v) - anything under that and it won't work, and anything much over that and it will burn out.
However there are many '5v' adapters designed to run from batteries available for less than £2. For example, 1.49p will get you a 5.0v 1A from 12v-24v 'car adapter', or even cheaper at 49p you can purchase a small PCB based DC-DC 'buck step-down converter' that will get you 5.25v from 7v-36v (which would also be suitable for PoE)

Remember the date and time. This is an 'annoyance'. The Pi gets it's time/date from the Internet (when connected) and even 'keeps count' so long as it's powered on, even if the Internet is no longer available, HOWEVER when it's 'powered off' the count is 'suspended' (when next powered on, it continues from where it left off until it can get an Internet update).

A RTC (Real Time Clock) plug-in circuit board can be had for less than £4 (eBay), however whilst they 'remember' the time (i.e. keep counting when the Pi is off) they don't 'find' the time (i.e. they have to be 'set', either by the Pi connecting to the Internet or by you setting them manually). Of course you can start with them plugged into a Pi B+/B2 with Internet access which will them 'set' the time, and then un-plug the board and move it to your 'unconnected' Pi Zero (or other non-Internet connected Pi).

The 'best' date & time solution, which 'sets itself', is a GPS plug-in circuit board (available for less than £10), although that does mean finding space for the aerial.

Deliver (5.1 surround) sound. The Pi Zero has no stereo output socket (in fact, the GPIO pins aren't even 'tracked' to the GPIO header). Like the other Pi's you CAN get audio (even 5.1 ac3) via the HDMI, but it's then up to the display to drive the sound system.

Since the Pi Zero lacks the 'stereo' socket, at first sight this makes the Pi Zero a rather poor choice for any 'audio' project (Internet radio, game / movie player), unless (of course) you happen to have a 'spare' HDMI display with built in surround sound drive capability = for example your main lounge TV :-) = in which case see how to set up the OpenELEC Kodi multi-media system).
It is, in fact, possible to 'build' your own 'stereo out' circuit for the Pi Zero by instructing the GPU to 'route' the audio outputs (PWM0_OUT and PWM1_OUT) to 'alternate' GPIO pins on the 40pin header (PWM0 to GPIO #18 (ALT5) plus PWM1 or GPIO #13 (ALT0) or GPIO #19 (ALT5)). For more details, visit here

However to get decent quality stereo output from any Pi, and especially the Zero, I recommend checking out the 'pHAT DAC' (cost about £12). The pHAT DAC was designed for the Zero but should be compatible with any Pi with a 40 pin header

Since Internet Radio is only stereo and most 'broadcasts' are .mp3 at 128mbs (which at least sounds better than the obsolete mp2 based terrestrial 'DAB radio' garbage), the Pi Zero should have no trouble keeping up (in fact, even the original A/B Pi could cope with 128mbps mp3 (just)).

Play anything other than decrypted HD (h264) movies 'out of the box'. If you want to play (unencrypted, i.e. pre-ripped) 'DVD standard' movies you will need the 'mpeg-2 licence' (£2.40 from the Pi foundation). The Microsoft HD (VC-1) Licence is another £1.20 (same source). In both cases, the Licence code is 'tied' to a single specific Pi serial number (and can't be 'transferred'). The Pi doesn't support any sort of decryption, so you will have to 'crack' any DRM on your PC first

Since standard DVD's are mpeg-2 and most 'Internet streaming' HD requires the VC-1 Licence, many kids (and their parents) are going to be introduced to the wonderful world of Licencing and DRM. Expect to see a lot of 'how to recode my mpeg-2 DVD into h264' enquiries on Google :-).

Connect to the Pi Touch Screen (or, Zero v1.0, the Pi Camera). Neither Touch Screen or Camera ribbon connectors exist on the Pi Zero ver 1.0 (none of the required i/o pins are even tracked out from the GPU). However the v1.3 has a 'micro-Camera socket' fitted to one end. With a suitable cable (cost about the same as the Pi Zero itself, or £1.28 from eBay) the Pi Camera can be attached

The Pi has always supported basic cameras via USB, which do 'work' (just). You also have access to the I2C and UART pins on the i/o header (as well as the AV PAL/NTSC 'TV video' (old RCA socket) pins), so a simple serial display (eg 16x2 line LCD) can be connected.

Note that the 'TV out' is tracked to a pair of holes marked 'TV' near the end of the GPIO header (next to the 'reset' switch holes, marked 'run'). The TV out signal is on pin 1 (the 'square' hole nearest to the 'TV' label) - the round hole is Gnd. Note you will need a SOCKET (not a plug) if you want to use a standard RCA cable :-)

The pages in this topic are :-

  + Pi Zero system costs

  + Developing with the Pi Zero == Latest changes (modified 18th Jun 2020 18:15.)

  + Using the Pi Zero - (as a USB device)

  + Using QEMU - (Pi emulation on your PC)

Next page :- Pi Zero system costs