[TriEmbed] ESP8266 Serial Connection

[Pete Soper]

This is nice information.

I looked at it a bit and one thing that jumped out and swatted me on the 
nose is the fact that the radio board 3.3v power supply current draw can 
greatly exceed the current an FTDI chip can put out. The "usual" FTDI 
chips (and it appears Sparkfun is using a vanilla FT232RL) can only 
source about 50ma at 3.3 volts from their internal regulators. The 
ESP8266 board has typical (i.e. possibly far from "worst case") current 
requirements looking like this (from the table on the web site linked to 
below):

802.11b, CCK 1Mbps, POUT=+19.5dBm 215mA
802.11b, CCK 11Mbps, POUT=+18.5dBm197mA
802.11g, OFDM 54Mbps, POUT=+16dBm145mA
802.11n, MCS7, POUT =+14dBm135mA
802.11b, packet size of 1024 bytes, -80dBm60mA
802.11b, packet size of 1024 bytes, -70dBm60mA
802.11b, packet size of 1024 bytes, -65dBm62mA
Standby0.9uA
Deep sleep10mA
Saving mode DTIM 1 1.2mA
Saving mode DTIM 3 0.86mA
Shutdown0.5uA

So a lot of the time you're basically trying to kill the FTDI chip. I 
personally let the smoke out of one of these by accidentally telling it 
to try to supply a motor controller (off by an inch with the wire in the 
breadboard and hit the wrong power rail). They will die if tortured enough.

So plan on the FTDI's 5v line driving an outboard 3.3v regulator with 
proper capacitors on both sides. An oscilloscope could confirm the radio 
is getting a proper supply and that it's not being yanked down by sudden 
changes in current demand.

-Pete


On 05/19/2015 11:00 AM, Christian Lilley via TriEmbed wrote:
> All of the information on the ESP8266 can be found here. 
> <https://nurdspace.nl/ESP8266>
>
> According to the wiki the baud rate should be 57600. Sparkfun does 
> mention that a level shifter should be used and that it should not be 
> connected directly to 5V sources.
>
> Here is an example 
> <http://allaboutee.com/2014/12/27/esp8266-arduino-code-and-circuit/>using 
> the Arduino's software serial to communicate with the ESP and the 
> normal serial lines to communicate with the FTDI board. This guy uses 
> a 9600 baud rate but I don't know if that is a custom setting he uses.
>
> Christian Lilley | Electrical Engineer
>
> *//*images <http://www.gomohu.com/>
>
> 919.794.8627 ext 129
>
> christian.lilley at gomohu.com <mailto:christian.lilley at gomohu.com>
>
>
> www.gomohu.com <http://www.gomohu.com/>
>
>
> On Tue, May 19, 2015 at 10:44 AM, Nathan Yinger via TriEmbed 
> <triembed at triembed.org <mailto:triembed at triembed.org>> wrote:
>
>     So, I have an ESP8266, a new serial adapter
>     (https://www.sparkfun.com/products/9873), and I'm trying to get
>     them to communicate.
>
>     When I power up the ESP8266, it creates a wifi network where I can
>     join and ping it, but as far as I can tell, reprogramming it
>     requires a serial connection.
>
>     When the ESP8266 is powered on, the 'tx' light on the serial
>     adapter flashes continuously, which I assume means the ESP8266 is
>     transmitting something. Nothing appears in my serial monitor
>     though, not even gibberish.
>
>     I'm using the serial monitor that comes with the Arduino IDE, with
>     various baud rates and line endings. I haven't found any
>     documentation about the byte length, parity, or character encoding
>     used by ESP8266. I get a TTYUSB device in /dev when I plug in the
>     serial adapter, so it appears to be doing something.
>
>     Does anyone know what's required to make the chips do something?
>     Or have a working setup they could bring to the next meeting?
>
>     Thanks,
>     ~Nathan
>
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