There are many types of optocoupler and you chose one based on the requirements of your circuit. My intention was to create a automatic shutter trigger for my Canon camera, so the circuit was a 5V Arduino and a Canon 40D which has about 3.2V on the shutter release connections. Due to the relatively low voltages there are many suitable optocouplers to pick from. I already had a Fairchild 4N26 so this is the one I used.
4N26
Optocouplers are digital switches. They work by using an LED emitter paired with a photo detector transistor. This means they can be used to allow one circuit to switch a separate circuit without having any electrical contact between the two. Basically, if you put a current through pins 1 and 2 and light the LED the photo detector transistor detects the light from the LED and allows a current to flow through pins 5 and 4. No current on pins 1 and 2 means current does not pass through pins 5 and 4.
Since I first posted about the HM-10 the firmware has been updated many times and some of the commands have changed. Therefore, I decided to redo the guide. For the main article I am using modules with firmware 5.49 (regular) except the one I am using for the firmware update guide which started with v5.40 and become 5.47.
There have been several firmware updates since this guide was written, as of March 2020 the latest is v707.
Updated 2019-08-25
I thought it was time for a minor update.
The latest zs-040 HC-06 modules have an updated firmware, hc01.comV2.0. This firmware has the following defaults:
– baud rate = 9600
– password = 1234
– nl/cr line endings not required.
– AT commands are required to be in upper case
– Firmware version = hc01.comV2.0
– Name = HC-06
– No parity
– SLAVE mode
Since the Bluetooth hardware is the same as the previous zs-040 HC-06s the Bluetooth specs are also the same. Bluetooth 2.0 EDR, SSP.
These use a slightly different BT module than the other zs-040 boards and there is a blue LED at the top left of the daughter board. Continue reading →
In the Connecting 2 Arduinos by Bluetooth using a HC-05 and a HC-06: Pair, Bind, and Link post I explained how to connect a HC-05 to a HC-06 so that when powered they automatically made a connection. Here we look at using that connection to get Arduinos talking over Bluetooth. Before continuing you need to have the Arduinos and BT modules set up as per the previous post. Here I am using 2 HC-05s. One in master mode the other in slave mode. The setup process for the slave mode HC-05 is the same as the HC-06 in the previous post.
Update 19.09.2015
The FC-114 boards I have have the Bolutek firmware. User DS has reported that he/she has FC-114 boards that have the linvorV1.8 firmware. So if the below does not work for you then check what firmware you have.
I may be missing something but I can not get the HC-05 FC-114 boards in to Master Mode and connect to other BT devices with just AT commands. The modules say they have accepted the commands, such as AT+ROLE1 but when I try to connect to other modules I get the error message “Can only be used in Lord Mode”.
The modules accept “AT+ROLE1” and report they have changed mode but they haven’t really.
In an earlier post I mentioned that it looks likes pin 27 or pin 28 has to be pulled HIGH to enter Master Mode and this does indeed seem to be the case. Everything I have tried without pulling the pin(s) HIGH has failed.
They reply with “OK” and if you interrogate with “AT+ROLE” they report “+ROLE=1” but they are actually still in Slave Mode.
Update 19.09.2015
The FC-114 boards I have have the Bolutek firmware. User DS has reported that he/she has FC-114 boards that have the linvorV1.8 firmware. So if the below does not work for you then check what firmware you have.
Since the HC-05 FC-114s and the HC-06 FC-11s share the same firmware the following should work on either module.
The default setting on start up is Slave Mode waiting for pairing or a connection and also accepting AT commands. This means it is fairly simply to start using AT commands.
I have just received some new HC-05 and HC-06 Bluetooth modules. These were sold as zs-040s which is the module I actually wanted but I received modules marked FC-114. They share the same breakout board as the zs-040 but have different pins soldered between the Bluetooth module and the breakout board and have a very different firmware.
The small push button switch still has traces to pin 34 and still pulls pin 34 HIGH, however, on the FC-114 boards, pin 34 is a regular IO pin and closing the button switch doesn’t do anything. On the zs-040 boards, closing the button switch and pulling pin 34 HIGH puts the modules in to AT mode. Since the FC-114 starts in AT mode this is no big loss.
The STATE pin on the HC-05 zs050 board is connected to the LED 2 pin on the small bluetooth module and the LED 2 pin is used to indicate when there is an active connection. This means the Arduino can connect to the STATE pin and determine when we have a connection. The STATE pin is LOW when the HC-05 is not connected and HIGH when the HC-05 is connected.
As a quick visual indicator you can put a LED + suitable resistor on the STATE pin. When the module is connected the LED will light.
You can also use the Arduino to read the value of the STATE pin.
The Arduino Mega has 4 hardware serial channels so we do not need to use software serial, we can use one of the extra hardware serials to talk to the Bluetooth module. In the below example I using serial1 to talk to the HC-05. Continue reading →
Controlling an Arduino over Bluetooth from Android using App Inventor 2
Here is an example of controlling the Arduino over Bluetooth using a HC-06 bluetooth module and an Android app. The example uses an Arduino Nano but other Arduinos will work just as well. A HC-05 module can be used stead of the HC-06.
The Android app was created in app inventor and the aia file can be downloaded at the bottom of the page.
Update:
This is a very old guide and things have moved on a lot since this was written. One of the main advances is the ESP8266 core for the Arduino IDE. This means the ESP8266 can now be programmed like an Arduino and this is how I use them now, no more messing around with AT commands. For a general overview and examples of using the ESP8266 with the Arduino core see ESP8266 and the Arduino IDE.
Here is my first attempt at a web server using the ESP8266. It includes a request count and also a text input field.
Following on from the FTDI + ESP8266 post, if you do not have a FTDI serial adaptor you can use an Arduino. Here is how to set up the Arduino to talk to the ESP8266.
Just started to play with the ESP8266-01 modules. Purchased from Taobao.
These, I believe, are version 2 and have the LEDs near the antenna. When first started they identify themselves as [Vendor:www.ai-thinker.com Version:0.9.2.4] and are version 018000902-AI03. This is a custom firmware from ai-thinker.
There seems to be quite a few different versions of similar modules. And the same module could have one of several firmwares.
In a previous post I showed how the HC-05 can auto connect to other Bluetooth devices by setting the HC-05 to pair with any device using CMODE=1. This is quick and easy but does not give any control over which other device the HC-05 connects to.
In this post I show how to set up the HC-05 to always connect to the same HC-06 (or HC-05 in Slave mode). For this we use PAIR, BIND, and LINK.
NOTE: There are now newer modules that use a 3.0-20170601 firmware. This guide does not work for these modules (AT+INQ gives an error). I do not have any of the new modules and cannot find a reliable supplier. I have ordered 3 sets of BT modules believing they were the newer ones only to receive old ones.
If you have not yet bought BT Classic modules. I recommend buying the original HC ones. These are slightly (just a little bit) more expensive but are well supported and full documentation is available. Original HC modules have the HC logo screen printed on the main BT board and the current boards have a blue LED top left.
I am using 2 separate Arduino IDEs; version 1.6.3 which is installed, and version 1.0.5 which I run from a folder (it is the non install version). This allows me to use 2 IDEs at the same time, each connected to a different Arduino. It also gives me 2 serial monitors, one for each Arduino.
The modules used are the zs-040 versions of the HC-05 and the HC-06. The HC-05 has the Wavesen/HC firmware 2.0-20100601 and any any module running the same firmware will be the same.
The HC-05 has 2 AT command modes which I refer to as “mini” AT mode and “full” AT mode and some commands only work when in “full” AT mode. To enter “full” AT mode pin 34 needs to be HIGH and kept HIGH. To accomplish this I have made a connection from pin 34 to +3.3v. See the diagram below (or after the jump).
Making a connection Between a HC-05 and a HC-06: Method 1
Using the CMODE command we have an easy way to connect the HC-05 and the HC-06 (or 2 HC05s). When the HC-O5 is configured to pair with any address (AT+CMODE=1) it should connect to a Slave module automatically. No binding etc is required.
I am using the zs-040 modules with firmware 2.0-20100601 and other modules with the same firmware will be the same. If you have issues check the data sheet for your module.
The Set Up
I am using 2 different Arduino IDEs; version 1.0.5 and version 1.6.3. This gives me 2 separate serial monitors. The Arduino connected to the HC-05 is on COM8 and the Arduino using the HC-06 is on COM17
