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  • Author Author: camuyano
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ESP8266 developing using an Arduino

camuyano

Currently I am playing with the ESP8266 WIFI module as many others are. Since I want to create some Arduino libraries for it, I am in the need to do some debugging. The Arduino only has one hardware UART. And if you wire anything to the atmega UART port you may run into problems when downloading new code to the Arduino. The Arduino programs the atmega via the hardware UART port and if something is connected it may cause trouble. For downloading you end up disconnecting and reconnecting the ESP module without mentioned that you loose the ability to use the Serial Console for debugging.

 

To solve this situation I now am using the SoftwareSerial library. Before all this I updated the ESP8266 firmware and the default baud rate is 9600 which is fine for the SoftwareSerial library.

My current setup is:

1. ESP8266 (ESP02) connected to a level shifter (to make 3.3V talks to the Arduino 5V). The level shifter I am using is a 74HC4050N hex non inverting buffer.

2. Wire pin 10, 11 via the level shifter to the ESP8266

3. Load a modified SoftwareSerial echo example to allow me to send serial commands from the Serial Monitor window to the ESP8266 via the arduino. Here is the link to the Arduino code for software echo.

I had it all wired without a level shifter but the SoftwareSerial library responded always like there were data available to receive when there were none. By using the level shifter all that "noise" went away and now I have a clean communication.image

 

What the code do is just wait for anything from the UART serial port and sends it via the SoftwareSerial port (pins 10,11) and back. This way I can upload new code to the Arduino, talk to the ESP8266 and get debug messages via the Serial console without having to rewire things.

I am just starting to use this module, but it looks very interesting. Just wanted to share my current setup in case anyone wants to code for the Arduino and ran into the same problem I did.

 

Sorry that my diagram do not have a pretty ESP8266 module drawing but you get the idea. Use the legend above the green connector to match your module.

 

Update:

With this same thinking I decided to try a more "permanent solution". So I am in the process of building an interface prototype board for this module. I decided to build a dedicated interface circuit board (no breadboard prototype, straight to production). I blogged about it here if you care.

 

This is how this setup looks in real life:

image

 

Note:

Verify your Arduino version maximun 3.3V supply current. The official Arduino Uno R3 can supply something like 150mA tops and that is not enough to make the ESP8266 work always. It may power up but not much more. Arduino compatible boards or clones may have different hardware with more power ratings. If not available then my recommendation is to get an external power source or to reduce the 5V power to 3.3V.

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  • Hi

    Some comments - using 9600 is fine - originally I thought that it might be a good idea to use 115k - but I was forced to use 9600 by the Lua firmware (and if you're not familiar with that, head over to my blog where you'll find lots on the subject) and actually it's not so bad - so - first things first - you absolutely MUST use level shifting, there is even a possibility of damaging the chip without it (unless of course you are using a 3v3 micro). You don't need it for the output from the ESP chip - but for input I took a 560r resistor from (in my case) the Arduino output to the ESP, then a 1k resistor from the ESP to ground, hence effectively limiting the input voltage - similarly with the reset - and at some point you will need the reset.

     

    As for serial itself, it is really worth considering unless you're on a REALLY tight budget, the MEGA boards, they have 2 UARTS so you don't have to worry about software UARTS and these boards from China are now as low as £8. Why is a software UART a bad idea? Well it depends on what you're doing but it uses interrupts and so again in the case of the simpler micros, if you're messing with anything else that uses interrupts you could end up with timing issues.  Personally I use `184-based boards a lot (own design) - 2 UARTs, 128K Flash and plenty of RAM.

     

    Anyway for anyone interested in the ESP8266 and the various boards such as the ESP-01, ESP-03 etc etc my blog has links to just about everything else and this morning I made some improvements to a serial terminal I put together specifically for messing with these boards.

     

    Great article, if only everyone would put in so much detail and a nice diagram.

  • in reply to scargill

    Level shifting is a must, I did a small breakout board for this matter (ESP8266 interface board on it's way (WifIco)) Still is a work in progress, I would do a revision of the board since it has a few errors. Also I plan on making a bigger independent board for a specific purpose. It is all just ideas and plans in my head, so I will post about them when they become reality.

  • in reply to scargill

    What are you doing with that module there Peter it looks like you put it at the focal point of a dish point out across the bay or was that just an accidental photo ?

  • in reply to Problemchild

    Not an accident John but a lot simpler than it looks. Last time I was in Spain (we have a house out in the wilds) I took the photo.. and it is the screen backdrop on my high-res PC screen. I stuck my hand in front of the screen with LED lighting lighting up my hand.. and took the photo :-)

     

    I agree it would have been more dynamic to actually be standing out in the country but this way was easier - and given that it's zero centigrade (freezing) in the UK right now, a lot more practical :-)

  • in reply to scargill

    I was up the Wrekin  reading this post this morning it was still -2 ish so was thinking of the balmy 0 degree weather you are having image

  • in reply to Former Member

    As Peter said, you only need level shifting when interfacing with 5v device. A level shifting circuit can be achieve by a lot of methods, from two simple resistors or zenner diodes, no inventing level shifter IC, some transistor, etc. Search for level shifting and choose the one you can make with the hardware you have.

    The official Arduino may not be capable to provice enough 3.3v to power the module but some of the Arduino clones can. Also there are Arduino compatible boards that runs on 3.3V and you will no need to do any kind of shifting.

  • in reply to camuyano

    I've tried with my mini pro 3v3 clone. Still no luck in talking with the ESP. I can send commands to the module, I can see the blue led light up when transmitting data, but the response I get to AT+RST command is always (int value) 255 255 255 255. RESET and CH_PD pin are connected to the VCC pin

    On other commands I get more or less same meaningless data.

    Maybe an upgrade of the firmware can solve the issue?

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  • in reply to camuyano

    I've tried with my mini pro 3v3 clone. Still no luck in talking with the ESP. I can send commands to the module, I can see the blue led light up when transmitting data, but the response I get to AT+RST command is always (int value) 255 255 255 255. RESET and CH_PD pin are connected to the VCC pin

    On other commands I get more or less same meaningless data.

    Maybe an upgrade of the firmware can solve the issue?

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