AI Thinker have obviously been listening …but the question is, to whom. They’ve just come up with something which they’re calling the “ESP8266 Black board T5” (their capitalization, not mine). It looks really interesting at first glance.
There’s a relay and a couple of screw-down connectors at one side of the board and what’s obviously one of the older (blue) DHT11 temperature/humidity sensors on another side, sitting next to an ESP13/WROOM-02 module. Between the relay and the DHT11 is a barrel-connector for DC input, but the unit also comes with a 3-cell (AA size) battery box attached via short flying leads (the board itself is just a little bigger than the battery box). There’s a beeper on the board and there are three LEDs arranged in a vaguely spoke (as in bicycle wheel) shape. In addition, there are two mini “tact” switches, a couple of jumpers, a slide-type on/off switch and, sitting like a spider in the middle of its web, a mysterious, 32-pin, QFP package chip. Etched along the edge of the board is “ESP822_IOT_DEMO” (sic) and also “AI-CLOUD INSIDE”.
As usual with the on-line auction site vendors, there’s b’grall useful information on any of the pages which I could find (and as the auction sites advertise it as an “ESP8266 Serial Development Board” it’s also next to impossible to find any useful information on the web, either). Anyway, just looking at the board I thought it had to be worth the $10 asking price, just in parts alone. With a bit of luck, the mystery chip might turn out to be an I2C expander or something equally useful. Throwing caution to the winds (poor old Caution!), I added a single unit (Caution must have crawled back home again while I was surfing dBay) to the next order I made for other odds n’ends.
Tum-de-dum-de-do. Wait for a couple of weeks. Odds n’ends arrive, along with da’ board.
Hmmm… Don’t recognize the number on the top of the mystery chip. Never mind, throw in some batteries and slide the switch to “On”. A red LED (which I hadn’t noticed in the pictures) lights up and, after a slight delay, the board starts to emit an annoying “Do something within the next few seconds, or I’ll explode” kinda’ beep. I press one of the buttons. It still beeps. I press the other button. It still beeps. I switch it off, hold down one of the buttons and switch it back on. It starts to beep again. Same procedure, but other button. Ahah! a single beep and then blessed silence …for about a second, then it starts to beep again. I rip the batteries out and throw the whole thing in a drawer (I was sorely tempted to throw it on the floor and stamp on it, but I thought I might damage the floor).
Back to the web (as there was b’grall documentation in the package, of course) and I resort to a Oogleg image search. Oogleg’s image processing may be wonderful, but it seems to think that this PCB is a dead-ringer for all sorts of weird and wonderful stuff on the web that just happens to have a black PCB. I finally find a link to AI Thinker’s forum and a thread which has some links to documents (Yay!), one of which seems to be an English PDF (double Yay!).
My yaying turns out to be a little premature. The English documentation is limited to the schematic and it’s a fairly useless one, at that. Many of the components evident on the board aren’t present on the schematic at all, labelling is haphazard, parts are wrongly identified (the 32-pin QFP is labelled as an STC15L2K16S on the schematic, but the part on the board is an STC15L2K32S2 [see below], the sensor is identified as a DH11, but the part on the board is definitely a DHT11) and plugs, sockets and jumper blocks are all depicted as unidentified rectangles. One thing that does stand out immediately though, is that most of the GPIO pins on the ESP8266 are unconnected. Uh-oh!
A P-Channel MOSFET (top R/H corner of the schematic) gives another clue to what’s going on here. The drive signal is labelled “WIFI_VCC”. It’s a supply-side switch for the ESP8266 power. The board is battery powered and it looks as though the ESP8266 is only powered up when a network connection is needed (and I recognized this simply because I’m doing the same thing with one of my ESP8266 projects, but using a DS3231 RTC module to drive the power switch).
So, it turns out that AI Thinker have produced a board which has a “master” microcontroller and is using the ESP8266 simply as a network interface.
Next to the on/off slide switch there’s a three-pin connector (barely visible in the photo above – it’s slightly above and to the left of the DHT11) with the silkscreen label “R-G-T”, which appears to be the serial port for the microcontroller (not for the ESP8266). I pulled the unit out of the drawer again just long enough to connect up the pins and go through the press-beep-disconnect routine a few more times at various baud rates. I didn’t ever get any indication of any output at all in the terminal window. Zilch! Nada! Nutt’n! At the same time I fired up a WiFi scan on one of my access points. I could quite easily see my neighbours’ access points going up and down, but no indication at all that the ESP-13 on the board was ever powered-up. Back in the drawer wi’thu useless burger!
I might possibly drag the thing out again and have a poke around with a multimeter, but not before I’ve de-soldered that bloody annoying beeper.
As far as I can tell from the scant information available for this microcontroller part number available on the web, the chip is an 8051 derivative, with 32K of onboard flash memory. I haven’t used an 8051 chip in twenty years and, although I’m sure there are some folks out there who will be positively salivating at the thought of an 8051 paired with an ESP8266, there will most certainly be many thousands more who will be scratching their heads and saying “WTF?”. I’m not (and probably never will be) an AVR/Atmel kinda’ guy, but why AI Thinker would AI Think it a good idea to produce a board for the hobby market with such an odd-ball chip is beyond me. If they’d dropped in an ATtiny85, a Propeller, an MPS430, a PIC18F/24F, or just about any low-end ARM chip they would have had the (ESP8266) world beating that proverbial path to their door. As it is, they’re destined to get a big, red “FAIL” stamp splattered across their collective foreheads. Anyway, if you’re at all interested, I finally found the data sheet for the chip on STC’s web site (no thanks to their total lack of indexing or search function and the quiet inclusion in one data-sheet — with a single processor ID as the only title — of 18 different chips). The highlights are, yes 8051 based, 32KB of flash, 2KB of SRAM, 29KB(Eh?!?) of EEPROM, 2 x UART, 3 x PWM, internal clock and 8-channel, 10-bit A-to-D. If all of that lights your fire, then this is the board for you (and I’ll sell it to you …cheap!).
Hold on just a second; I need to go and add a “Double Duh!” category for this one.
Update – In an effort to introduce some semblance of balance into this post (and especially to note that I’m not, generally “anti” AI-Thinker), I’d like to point you at a couple of articles on one of their other boards, which actually is something of a bargain! Just about the only thing it has in common with the “T5” is a long and overly complicated name, but you should definitely keep an eye open for the ESP12-based “Yellow Development Board”. Apart from anything else, it has lots of nice flashing LEDs and you don’t need to resolder anything to get them working.