First, the good news… Espressif have released an updated (as of June 1st 2015) documentation package on their web site:- http://bbs.espressif.com/viewtopic.php?f=21&t=412
My initial impressions (from the datasheet for the ESP8266EX chip and the hardware guide) is that the English language versions are very much improved from the early releases and definitely worth your time to download. The datasheet especially now has several very clear, easy to understand tables, showing the pins by function. This very much helps to reduce confusion as, for instance, if you want to use I2C you only have to scroll down to that section and deal with a table listing two pins (all you’re interested in).
The new revision of the datasheet certainly seems to have fewer instances of ambiguous wording and is generally much easier to read. There seems to be a lot more useful information in there, too (but that may be because I’ve failed to keep up with the earlier published revisions). The hardware guide has quite a bit of useful information on layouts and PCB design issues, as well as information on the ESP-WROOM-01 (that fabled beast with the normal-sized header pins).
And next, the not quite such good news… Espressif have released SDK 1.10 (and patches to it, already) and, as we are all now becoming increasingly and frustratingly used to, have broken just about everything in sight. Again.
Initial reports are that existing code fails to compile with errors referring to the PULLDWN register settings for GPIOs. These have apparently gone away completely. The Espressif posting on the change states that, “Note: There are no pull-down functions on GPIO pad now, so we should never use these registers. Add external resistance to pulldown the pin.“. It is unclear to me whether the wording refers to all GPIO pins, whether the pull-downs were there originally and have been removed in later versions, or whether they were there originally and have just decayed over time. The updated datasheet for the ESP8266EX chip says specifically, “Each GPIO can be configured with internal pull-up (except XPD_DCDC, which is configured with internal pull-down),…“, so there almost certainly is at least one pull-down, maybe, possibly, perhaps.
As usual, Pete Scargill is doing a great job of disseminating the latest information on what’s happening on the issues around this latest SDK (and his site is always worth a regular visit for ESP8266-related updates, anyway).