Category Archives: Arduino

ESP8266 NodeMCU Backdoor uPWM Hack for IR signals

We received our ESP8266 NodeMCU several months ago it has been difficult to find a working example of Hardware PWM to generate crisp Infrared carrier signals. Most posts we have read suggest that there is no PWM readily available on any of the supported platforms. As we have already shown with Arduinos and the Particle Photon we figured it would be possible to use a spare UART pin on the ESP8266 NodeMCU to achieve our goal.  After some initial success we encountered some watchdog timeouts/resets and it seemed like the uPWM hack would not be possible on the ESP8266 Node MCU platform. For a few weeks we ‘parked’  the effort and today we decided to try again with all of the latest and updated firmware available from the ESP8266 community via the Arduino IDE. This time we were successful and the ESP8266 NodeMCU Backdoor uPWM Hack for IR signals using works!

ESP8266 NodeMCU uPWM Inverted IR Circuit
ESP8266 NodeMCU uPWM Inverted IR Circuit

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Sending long AC Signals from Flash with IRremote

One of the most popular projects involving Infrared remote control, is to use an Arduino to control an Air conditioner (AC) system. However, AC signals are usually very long and take up a lot of SRAM on a standard Arduino. Experienced users will go about reverse engineering the AC protocol to make the sketch fit within the 2K Bytes of SRAM. Many hobbyists will struggle, even with the help of tools like AnalysIR to guide them. In this post we cover sending long AC Signals from Flash with IRremote. IRremote (along with IRLib) is a popular open-source library for sending and receiving IR remote control signals with Arduino. The demo code covered in this sketch extends our previous sendRAW example by demonstrating how to store many long AC signals in Flash with little or no SRAM overhead.

AnalysIR screen-shot showing the signals captured from the sendRAW_Flash sketch
AnalysIR screen-shot showing the signals captured from the sendRAW_Flash sketch (click or more detail)

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Troubleshooting the Big Button Infrared remote control with AnalysIR

Marco is  a volunteer for an organization (NSW Australia) that builds custom aids for people with disability, and has recently been looking at a project to create a ‘very large button’ IR remote control for a cable TV Set Top Box (STB). The custom unit needed basic functions (Channel Up/Down, Volume Up/Down and Power On/Off). Commercially available large button remotes have buttons that are still too small and/or they have too many buttons. Soon he hit a roadblock trying to capture some difficult Foxtel signals and searched all over the web looking for a solution. Needless to say, nothing worked out for him until he came across AnalysIR via Google. Once he started Troubleshooting the Big Button Infrared remote control with AnalysIR the root cause of his problems became obvious.

Troubleshooting the Big Button Infrared remote control with AnalysIR
Marco’s Big Button Infrared Remote control

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Backdoor uPWM Hack on Photon for Infrared signals using UART

Since we received our Photon several months ago it has been difficult to find a working example of Hardware PWM on the Photon. Initially, we ported our softPWM approach to the Photon, which is excellent. However, we figured it must be possible to use at least one of the spare UARTs on the Photon to achieve our goal. So first we started prototyping on the Arduino and quickly got a working example with some limitations – only 40 kHz and 33 kHz carrier frequencies were possible with the UART without delving into the registers a bit more. Then we moved the code over to the Photon, leveraging our previous softPWM examples, upgraded with the Arduino code – EUREKA! The Backdoor uPWM Hack on Photon for Infrared signals.

uPWM Circuit diagram for Photon
uPWM Circuit diagram for Photon using UART

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Preview: A.IR Shield, a high-end Infrared Shield for AnalysIR, IRremote & IRLib

The fifth member of our MakeIR series of devices & kits is the A.IR Shield. This shield works out of the box with AnalysIR and is essentially plug & play , with additional prototyping options. The shield comes attached to an Arduino nano compatible device (clone). Although designed specifically for AnalysIR, users can also upload IRremote, IRLib or any Arduino sketches that run on the Nano. A.IR shield is built with only the highest quality IR components available and boasts dual Infrared emitters with configurable IR Power.

A.IR block diagram
A.IR Shield Nano block diagram

We have provided a link below to the preliminary product data sheet and would welcome feedback on additional, nice to have or missing features, if any. Please read the data sheet for a more detailed description of the A.IR shield. Continue reading Preview: A.IR Shield, a high-end Infrared Shield for AnalysIR, IRremote & IRLib

Simple Infrared PWM on Arduino, Part 2- RAW IR Signals

In Part 1 of this series, we demonstrated how to send signals using simple Infrared PWM on Arduino. In this Part 2 post we look at sending RAW IR signals – specifically a RAW NEC signal and a longer RAW Mitsubishi Air Conditioner signal. We have also improved the method shown in Part 1 due to some issues we identified when sending ‘real’ signals versus the ‘test’ signal we used before. (More on that later). In Part 3, we will take the signals from this post and show how to send them using their binary (or Hex) representation, which saves lots of SRAM.

Original NEC 32-bit and Mitsubishi 88-bit Signals displayed using AnalysIR
Original NEC 32-bit and Mitsubishi 88-bit Signals displayed using AnalysIR

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Simple Infrared PWM on Arduino

We are often asked on discussion boards, about conflicts between IRremote or IRLib and other Arduino Libraries. In this post, we present a sketch for ‘Simple Infrared PWM on Arduino’. This is the first part in a 3 part series of posts. Part 1 shows how to generate the Simple Infrared PWM on Arduino (AKA carrier frequency), using any available IO pin and without conflicting with other libraries. Part 2 will show how to send a RAW infrared signal using this approach and Part 3 will show how to send a common NEC signal from the binary or HEX value.

Example 56kHz generated Infrared signal @ 50% duty cycle
Example 56 kHz generated Infrared signal @ 50% duty cycle

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Driving an Infrared Led directly from an Arduino Pin

logobutton200x200A common question asked on forums is one about – Driving an Infrared Led directly from an Arduino pin.  Although the answer may be obvious to anyone with at least a basic knowledge of Ohm’s Law, many are confused about how to choose a resistor value for optimum performance. Often, there is a debate about whether a resistor is required at all, given that the AVR pins are rated to deliver an absolute maximum of 40mA on a pin. (Note: All of the quoted specs in the data sheet are for test conditions of up to 20mA on a pin). Of course there are better ways to drive an IR LED with a transistor circuit or even a constant current circuit. However, in this post we consider only the direct drive circuit using a current limiting resistor, as illustrated in the diagram down below.
Make sure to read the caveats at the end of this post.

Analysis of Voltage & Current for Infrared Led driven by Arduino
Analysis of Voltage & Current for Infrared Led driven by Arduino

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Controlling Chigo Air Conditioner via Infrared from smart phone

Anyone who has tried  controlling an Air Conditioner unit using an Arduino, USB IR Toy, RPi or any MCU will know how difficult it can be to record the longer infrared signals they use. Typical TV systems use IR signals circa 32 bits long, while this Chigo AC unit uses a signal with 197 marks & spaces (or 97 data bits). One of our users, Sertunc – from Istanbul in Turkey, reported his success using AnalysIR to easily record the signal timings for his AC unit and sent us the details along with some nice photos. After testing the validity of the recorded signals using an Arduino, he then set about loading the signals onto his Samsung smart phone (models S4, s4 mini, S5 and more supported). This was helped by installing the free ‘Samsung IR – Universal Remote‘ app onto his phone via Google Play.

Samsung IR Remote appSamsung IR Remote app

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Poor maker’s Infrared receiver #2

Our recent post about the silver bullet IR receiver proved very popular and we promised that we would follow-up with another variant of the poor maker’s Infrared receiver. This time we are using an IR Led (emitter), 2 resistors and any standard Arduino. You will also need to download the Arduino code provided below, compile and upload it. One of the most common problems encountered when trying to decode IR signals is that makers don’t always have the appropriate IR receiver for the job in hand or have to wait for one to be delivered by mail. Here we present an affordable method to allow you to use any IR emitter (LED) as a receiver and as a bonus we are publishing the Arduino code to make it all work.

Circuit Diagram: Poor maker's IR Receiver
Circuit Diagram: Poor maker’s IR Receiver

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