Arduino, HM-10 and App Inventor 2: Adding a slider

This post continues the Arduino, HM-10 and App Inventor 2 guide. A few people asked about adding a slider so here it is. Please beware; this is not a basic guide for using a slider in App Inventor 2. I am adding a slider to an existing app and have certain things (semi advanced) that I want to achieve.

Arduino_HM-10_AI2_Adding_Slider_33 - updateApp_04

In the previous guide we created a basic Android app to control 3 LEDs. The app was developed in such a way to make adapting it as easy as possible. So let’s see if that is true and add a slider to control the brightness of one of the LEDs. We start with extending the app and then update the Arduino sketch.

Using the same command method as before, we will create an ascii command and send it to the Arduino. The command will be in the form “[Snnn]”. Where S is used to denote slider and nnn is a value from 0 to 255, or more specifically “000” to “255”. The Arduino will read the command and set the LED brightness accordingly. Using ascii for this keeps things fairly simply but it is not the fastest way to do it. The slider value will be from 0 to 255, this is actually the same value range as an 8bit byte. Using the ascii command we need 6 characters (including the square brackets). To send the actual value only would require 1 character (2 with a label/marker character). If all you are using is a single slider then there is no reason to use ascii.

Continue reading

Create A Bluetooth Joypad With App Inventor 2

BluetoothJoyPad_draftLayout_01_800Here we create a basic Classic Bluetooth joypad for use on an Android device to control a microprocessor (Arduino) connected to a Bluetooth module. The app is fairly simply. There are 2 screens; the first is the main control panel and the second is a connection page.

When the CONNECT button on the main screen is clicked the second screen is opened to allow the user to connect to a Bluetooth device. The direction buttons, when clicked, transmit codes to the Arduino.

Continue reading

Arduino, HM-10 and App Inventor 2

Hopefully this guide will give you a good introduction to using the HM-10 with App Inventor 2. I also hope that this takes you beyond the usual starter guides that do not go past very basic information.

Although I am using an Arduino the principles will be the same for any other microprocessor or indeed for using the HM-10 on its own. Warning: This is going to be a very long post.


To use this guide you should be somewhat familiar with App Inventor, have a BLE enabled Android device, and of course have an Arduino and a HM-10.

Continue reading

Switching Things On And Off With An Arduino

One of the first projects many people new to the Arduino do is blinking an LED and there many many guides on line. Unfortunately, many of the guides never go beyond the very basic first sketch. In this guide, I hope to help new users take the next step.

Besides the obvious fact that blinking an LED is cool in its own right it is a good exercise because switching an LED on and off is the same process for switching any digital device on and off. Once you can create the code to blink an LED you can create code to turn anything on and off. Of course, you do not need to control an LED, you can use the same methods to do almost anything that is controlled in the same way. For example, I use similar techniques when setting up remote controls using Bluetooth and wifi connections and instead of setting a pin state I send control codes.


Polling vs interrupts
Connecting Arduino pins directly to vcc
Polling. Example 01: Very simply press for on, release for off
Polling. Example 02: Press for on, release for off. Slightly refined
Polling. Example 03: Toggle switch
Polling. Example 04: Multiple states from a single push button switch
Polling. Example 05: Start and stop an action
Interrupt. Example 01: Turning an LED on and off
Interrupt. Example 02: Turning an LED on and off with debounce

Continue reading

HC-05 with firmware 2.0-20100601

There are now many cheap and no brand HC-05 modules that use the 2.0-20100601 firmware and rather than keep making the same post for different modules I will have a single main post which, as I update and add to it, will become a single point of reference.

The 2.0-20100601 firmware is originally by HC/Wavesen and as the version number may suggest it is from 2010. I am not sure if other manufacturers use it under license or simply copy it since the genuine HC/Wavesen modules now use version 2.1 firmware.

HC-05 with 2.0-20100601: AT Command Mode
HC-05 with 2.0-20100601: Connecting to an Arduino
HC-05 with 2.0-20100601: Initial Communications Test
HC-05 with 2.0-20100601: Main AT Commands
HC-05 with 2.0-20100601: AT Commands Dealing With Connections
HC-05 with 2.0-20100601: Making A Connection

Continue reading

HC-05 (ZG-B23090W) Bluetooth 2.0 EDR modules

HC-05 - ZG1643 - B23090W_001_800The HC-05 (ZG-B23090W) uses a regular Bluetooth smd module based on the csr BC417 with a MX 29LV800CBXBI-70G flash memory chip. It appears to be using the HC/Wavesen 2010 firmware and a Google search for “HC-05 2.0-20100601″ should give you plenty to read, including some of my older posts.

I have received a few comments about HC-06 and HC-05 modules that use a new breakout board (new to me at least). When I received the first comment I hadn’t seen these modules, by the time I had received the 4th or 5th comment the modules were all over Taobao so I decided to order a few (2 x HC-06 and 2 x HC05). I have no real use for these except to see if they are different to previous versions.



HC-05s are Bluetooth 2.0/2.1 EDR devices that have a serial UART layer on top of the Bluetooth. The UART layer makes them easy to use but hides the Bluetooth functions from the user. This is good if all you want is to make 2 things talk to each other. The HC-05 has two modes of operation; AT command mode and transmission mode. When in AT command mode all data received over the serial UART connection is treated as a command, and when in transmission mode, all data received over the serial UART connection is treated as data.

When in communication mode, if there is an active connection the data is broadcast to the connected device. If not connected, the data, disappears in to some mysterious void.

The HC-05 can operate as either a slave or master device. Slave devices cannot initiate connections, they can only accept them. Master devices can initiate and (depending on the actual module) sometimes accept them. If you want to use the module with a mobile device such as an Android phone, the phone will be the master device and so the HC-05 will need to be the slave. If you want to link two HC-05s, one will need to be a master and the other one a slave.

Continue reading

HC-06 (ZG-B23090W) Bluetooth 2.0 EDR modules

HC-06 - ZG 1643 - B23090W_001_800The HC-06 (ZG-B23090W) uses a regular smd Bluetooth module based on the csr BC417 chip with a MX 29LV800CBXBI-70G flash memory chip. The firmware is well documented and a Google search for “HC-06 linvor V1.8″ should get you more than a few hits.

I have received a few comments about HC-06 and HC-05 modules that use a new breakout board (new to me at least). When I received the first comment I hadn’t seen these modules, by the time I had received the 4th or 5th comment the modules were all over Taobao so I decided to order a few (2 x HC-06 and 2 x HC05). I have no real use for these except to see if they are different to previous versions.

The HC-06 is a Bluetooth 2.0/2.1 EDR device that has a serial UART layer on top of the Bluetooth. The UART layer makes them extremely easy to use but hides the Bluetooth functions from the user. This is good if all you want is to make 2 things talk to each other.

The HC-06 has 2 modes of operation; AT mode and transmission mode. When the modules are first powered on they go in to AT mode. Here AT commands can be entered via the wired serial connection. After a connection has been made the modules go in to transmission mode. Here everything the modules receives via the wired serial connection is sent to the connected device. At commands cannot be entered again until the connection is broken.

HC-06s are slave only modules and require a master device to make a connection. Slave devices cannot initiate a connection which means you cannot link 2 HC-06s together. The master module is the HC-05 which can be either slave or master. Since the price for the HC-05 and the HC-06 is basically the same I would suggest buying HC-05s and not HC-06s.

Continue reading

ESP8266 and the Arduino IDE

Updated: 30.10.2017
The old guide was out of date and had become a little messy and I had been thinking about redoing it for a while. Also, how I use the ESP8266 has changed and since I am using one as part of a IOT Word Clock I am currently building I thought I would update the guide. So, here is the all new version 2.0. The post for the IOT Word Clock will come later, probably much later…

When the ESP8266 first came out there was a lot of excitement and buzz. Here was a new chip that was cheap and allowed internet connectivity. I got caught up in all the excitement and bought several different modules. I intended to use them in various projects where I wanted some kind of remote control. Things didn’t go as planned though, I found the AT command interface very clunky and the ESp8266’s not very reliable. I put the ESP8266s away in the bottom of a draw and moved to Bluetooth.

Things changed when the ESP8266 core for the Arduino IDE was released. This meant you could program them as if they were Arduinos, no more messing around with AT commands. Programming the ESP8266s via the Arduino IDE made things a lot easier and it meant that in many cases you no longer required an Arduino.

Continue reading

ESP8266 and the Arduino IDE Part 2: Control an LED from a web page using Access Point Mode (AP)

In the first part I explained how to set up the IDE and got the basic blink sketch working. Here I go through building a web page control panel to control the LED remotely. I will start with a basic web page and then slowly refine it so we end with a simple but elegant control panel.

For this example I will be using the ESP8266 as an access point (AP Mode). This means the ESP8266 will create its own little network which we can connect to. The ESP8266 will then serve a small web page which we can view on a mobile device or any web enabled device such as a laptop.

I still have the LED connected to pin D1 but now I want to turn it on and off from a web page viewed on a mobile device. The web page will need 2 buttons, one for on and one for off. It would be nice if it also showed the current LED status. Something like “LED is on” and “LED is off”. Since this is a first example of a web control the actual web page should be as simply as possible.

I won’t go in to detail about creating web pages, if you are new to this there are many other sites to help you.

Continue reading

ESP8266 and the Arduino IDE Part 3: Control an LED from a web page using Station Mode

In the previous part we used the ESP8266 in Access Point mode where the ESP8266 generated it’s own mini network. Here we get the ESP8266 to connect to an existing wifi network. To do this we use the ESP8266 in Station Mode (STA). Switching to Station Mode is done by the library automatically so we do not need to mess around.

When using the ESP8266 in Station Mode, the connecting device has to be connected to the same network as the ESP8266. In AP mode, since the ESP8266 creates its own network, other local networks don’t matter.


Continue reading

ESP8266-01 Programming Breakout Board

Here is my 5V ESP8266-01 programming breakout board.


I am now programming the ESP8266’s via the Arduino IDE and I found using bread boards and wires was annoying, especially because I have a habit of VCC and GND mix up. I have a small pile of dead ESP8266-01s, dead due to shorting them while moving wires around. They are next to the pile of Arduino Nanos I have killed for the same reason.

Since starting to use the ESP8266’s again I have made a couple of breadboard friendly breakout boards. Version 1 worked but moving wires was inconvenient (the ESP8266 was in the way). Version 2 was better but I still had to mess with power, resistors and lots of wires. This lead me to version 3. A fully self contained programming breakout board.

Continue reading

Arduino with HD44780 based Character LCDs

Updated on 2017.04.29.

Arduino Libraries
Parallel Interface: Getting Started with a JHD162A 16×2 display
I2C Interface: Getting Started with a J204A 20×4 display with I2C daughter board
Creating custom characters


HD44780 compatible LCDs come in many shapes and sizes and two very common ones are the 16×2 and 20×4 characters. Although most screens come with a back light some do not. And although the original interface is parallel some screens come with an I2C adapter/daughter board pre attached (you can buy the I2C adapters separately).

A 16x2 and a 20x4 character LCD display

A 16×2 and a 20×4 character LCD display

Continue reading

Arduino with Optocouplers

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.



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.

Continue reading