One of my long-standing favourite shops in Tokyo’s famous Akihabara district, Akizuki Denshi, has just started selling the WROOM-02 (that’s Espressif’s own version of the ESP-13, just in case you haven’t been paying attention) with an adapter PCB kit which brings out the pins to a breadboard-friendly connection. It’s quite novel.
The kit comes with the WROOM-02 already soldered onto the board, but the header pins (although included in the package) need to be soldered to the PCB by the purchaser. The kit (including the WROOM-02) is priced at a very reasonable 680-Yen (that’s about $5.70) plus shipping. Unfortunately, they don’t ship internationally.
As you can see from the photo of the bare PCB, all of the pins are broken out to the adapter (including the three, separate grounds). As far as I can tell from the photos and from the text, there are no pull-ups or pull-downs; just the pin connections and nothing else.
Akizuki have a long history of producing kits and PCBs for the hobby market in Japan and a look at the “kit wall” in their shop is a good, barometric indicator of what’s hot in the embedded community here (of course the challenge is actually managing to elbow your way in there to be able to see it).
The WROOM v2 (aka ESP-13, aka ESP8266MOD) is becoming readily available on most auction sites, although hard details regarding memory/flash sizes are not easily found (rumours abound).
This little beastie uses yet another different form-factor and yet another different pinout. The pitch of the castellated pins is 1.5mm, meaning it (along with its bretheren) doesn’t fit onto a normal breadboard and it won’t fit onto any pre-existing PCB designed for any of its predecessors, either (including the WROOM-01).
Currently, doing a search on eBay for “ESP8266” and sorting by lowest price, brings up the ESP-13 at the top of the list, with one vendor selling them at $2.89 (with free shipping). That’s a pretty good deal even if the memory/flash sizes are still the same as the previous models.
Update #1 – Pins – The ESP-13/WROOM-02 modules have 18 pins available, as opposed to the 16 pins on the normal ESP-12 modules (yes, I know the ESP-12E has more). However, two of the pins on the ESP-13/WROOM-02 are extra ground pins (duh!), so effectively it has the same number of pins as a standard ESP-12, but is more difficult to solder because of the reduced clearance between those pins. 😦
Update #2 – I noticed recently that these modules have started popping up from some of the Amazon vendors. This seemed like good news, especially as the prices weren’t too much above the eBay/Alibaba ones. The first vendor I tried had “In Stock” marked on the Amazon page and a very competitive price. With the normal Amazon turn-around on shipping it seemed like a good deal, so I ordered a couple. The order was mixed in with some other stuff and I got a normal, automated “We’ve received your order…” email immediately after submitting it. Unfortunately, the next email, from the ESP13 vendor, said “Shipping via CHINA post”. Duh! If it looks too good to be true, it -is- too good to be true.
Well, the next (Amazon) vendor I tried had a web-shop with the same name, based in the country where I live and stating (on their shop page) that the WROOM-02 modules were in stock. The price was a little higher (although not much) than the first vendor, but I thought I’d give them a try and see whether they shipped the ESP-13 or the WROOM-02. This time I got the modules (via normal post-office delivery, not Amazon’s normal delivery service) two days later. The modules were genuine WROOM-02’s. Yay! This vendor is here in Japan, so if you use amazon.co.jp I can recommend “Microtechnica” as a vendor (or you can go directly to their web shop at http://www.microtechnica-shop.jp/). If you’re not in Japan, it’s still worth checking your local variant of the Amazon store to see whether the ESP8266 has started showing up; just try to make sure that any vendors you find have local stock and aren’t just “fronts” for someone shipping (slowly!) from China.
Update #3 – As per the previous update, I now have a couple of different versions of this module to play with. The first thing that I noticed is that the ESP-13 and WROOM-02 are not identical. The WROOM-02 has a much cleaner overall finish. In particular, the metal RF shielding is much neater, with a brushed aluminium finish, sealed corners and a neatly trimmed and soldered bottom skirt. The ESP-13 on the other hand, has a fairly ragged RF cover, with the uneven bottom edge of the skirt getting very close to the pins in several places. If you’re hand-soldering these modules, the WROOM-02 is much easier to deal with. On the ESP-13 you might want to check with a multi-meter whether there are any shorts between the pins and the RF shield.
Update #4 – Continuing on with the soldering story… Hand soldering these modules (both the ESP-13 and the WROOM-02) onto strip-board using flying leads of thin wire is a pain in the proverbial. Because there are more (side) pins than on the ESP-12 and because they’re closer together (smaller pitch), you need to use longer flying leads (the thin wires between the strip-board and the module pins) and they need to be angled more acutely (the leads to the centre pins of the module are almost straight, but as you move out towards the ends of the modules, the distance between the strip-board hole and the corresponding module pin becomes greater and greater, requiring a longer lead with a more extreme “S” bend in it). It’s do-able, but I wouldn’t want to do very many of them.
However, help is at hand. Eldon R. Brown, over on his blog, has come up with a very neat adapter board design which overcomes the biggest bugbear of most of the other adapters out there, namely that the resulting module+adapter is so wide as to make it impossible to connect to on a normal solderless breadboard, as it covers all of the available holes. Eldon’s design uses surface-mount header pins to tuck the connections back in underneath the module, giving it the effective footprint of an 18-pin DIP chip. Nice one, Eldon!
Eldon has made his adapter available as a shared project on OSH-Park, so I’ve ordered up a few (and some of the SMD header pins, too). I’ll let you know how things turn out with them.
Update #5 – The data-sheet from Espressif for their WROOM-02 states that the external flash memory chip used on that module is 4MB (see comments, below).