Hi
a few weeks ago, me and a few of my colleagues have decided to buy ESP8266 based WiFi modules and test them, just being curious what they are capable of. Well, as we've learned today, they are capable of pissing not only one engineer really off.
We bought two models of the modules: that cheapest rubbish with the nonshielded board and onboard etched antenna, this:
http://www.aliexpress.com/item/1pcs-ESP8266-remote-serial-Port-WIFI-wireless-module-through-walls-best/32280714838.html and one looking much better:
http://www.aliexpress.com/item/ESP8266-serial-WIFI-model-ESP-07-Authenticity-Guaranteed/32226744057.htmlI'd like to share an experience with these modules and some subjective review based on short toying with these modules.
As an engineer, the firs think you will likely do is to search for documentation. We have found only some marketing rubbish pdf, which mostly doesn't help with anything. Search for a datasheet specific for the two modules gave us no result. Nothing's been found. Only some "OHSW arduino type" schematic plans using silly images of the components not standardized schematic symbols.
Connecting the module. Looked to be easy. 3V3 supply, ground, RX, TX and that CHPD (chipselect/powerdown) signal tied to VCC. Cause the "OSHW arduino schematics" even were much consistet with how to connect Rx and Tx pins (some "instructables" were to connect Rx to Rx and Tx to Tx), a simple resistor loading test were conducted. Of course, Rx is the input on the module, Tx the output respectively.
By the way, the chip on the unshielded module gets hot rather quickly - don't understand that at all. And also two decoupling caps were installed on the module - seemed none is there. (wtf?!)
Trying to send an AT command. Seemed easy, until... the fuck what speed does the bastard use? "OSHW inctructables" also weren't much clear about that, nor you will get that from the pdf immitation of datasheet. I mean this:
https://nurdspace.nl/images/e/e0/ESP8266_Specifications_English.pdfAfter some time labouring with the speed setings in the terminal, the colleague's unshielded module caugth somewhat working at 9600 8N1. But the web instructed mostly using speeds like 115200 or 57600. But the fun haven't ended there. My shielded module has been just sitting there doing nothing. Only lighting the red LED.
Troubleshooting the metal can module. I have noticed, that sometimes on power-up, my metal-can-shielded module produced some glitch in the terminal, puked there some random characters, regardless of the speed was set. I couldn't make tha sucker print anything normal at any speed from 600bps to 115200. Then I grabbed a DSO a look at the mess on the TX pin. Looked definitely like UART signal. I have decoded first two characters and got 0x0D 0x0A. (CR LF)... Then I calculated the speed. 13.2us per bit.
Roughly 75700. Wtf shit is that speed? Some chinese standard?
Trying to communicate with the metal-can module. After setting the terminal to 75700 it finally produced some readable text. Some module ID, two-number bootcode (dunno what that means but gave me I think 7,7). Nice. Then I tried typing AT. No response. Then tried AT+RST. Nothing again. Then I started messing with CR/LF line endings. Nothing doing anything. Only gettin that short infotext message after reset or powerup.
Another web search followed. I learned, that the modules comes with differnt firmwares. And you simply don't know, which one you have in, when you buy the module. So you must first flash it using some (as I read on the web) very buggy flasher tool, which even doesn't support COMs with higher number that 6.
I haven't tried to flash the gizmo with anything so far, so stay tuned for update. Quick sniff into the web raised some alarms, that the flashing procedure isn't just that simple.
To sum up the today's few hour mess-around with these modules, I'd say these are pretty crap and an example of BAD product design. Yes, they are cheap, OSHW, Arduino, anything, but more trouble than helpful. Pretty disappointed