Mcp23017 interrupt example

It also shows you exactly how to use interrupts which is very tricky as there are some problems solved here in using existing Arduino code. Arduino or PIC devices and they even include interrupts. For some applications it could be a bit over the top; For example if you only want to control outputs a 74HC would be cheaper.

The IC2 version operates at kHz, kHz and 1. It also operates from 1. Having interrupt outputs is one of the most important features of the MCP, since the microcontroller does not have to continuously poll the device to detect an input change.

Instead an interrupt service routine can be used to react quickly to an input change such a key press etc. You can also mix and match inputs and outputs the same as any standard microcontroller 8 bit port.

The overall sink current is mA Vss and overall source current is mA. Download the datasheet here.

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The above specification shows that the device is quite capable of driving current to LEDs however there are 16 outputs so the maximum output current for the whole device has to be shared by all the LEDs. This also assumes that you are turning the LED on when it is driven low. Note: Choose a lower current to keep within limits. Remember that different LED colours have a different forward voltage drop when driven this is constant due to how a diode behaves so to control the forward current you have to specify the correct current limiting resistor for the voltage source used.

TIP: If your MCP is getting hotthen look at the overall output current from the chip by calculating the current from each pin and then adding up these results. If it is more than mA then reduce the current by increasing the current limiting resistors for each pin.

Obviously reducing the number of outputs in use will allow increasing current up to a maximum of 25mA per pin but then you could drive only 6 pins at full current! You must always to keep the maximum overall output current for the chip within the mA limit otherwise the chip gets hot and will probably fail.

The fact that the MCP gets hot is not a problem if you keep the maximum overall current consumption to mA. You should look at the data sheet for the maximum temperature allowed, and measure the chip temperature at its surface. The data sheet, usually, I did not look in this case, also specifies a de-rating parameter or graph so that if used within a hot enclosure or any environment you have to reduce the maximum current consumed!

The has three input pins to allow you to set a different address for each attached MCP Addresses available are specified in the I2C control byte and each device is selected by the I2C sequence below:. The above corresponds to a hardware address for the three lines A0, A1, A2 corresponding to the input pin values at the IC. You must set the value of these hardware inputs as 0V or high volts and not leave them floating otherwise they will get random values from electrical noise and the chip will do nothing!

The four left most bits are fixed a specified by a consortium who doles out address ranges to manufacturers. This is the same scheme for most microcontrollers - the key is to remember that zero '0' equates to the 'O' in Output. Reading the OLAT register bit returns a 'one' as you would expect from a software engineering point of view. This reduces the glue logic needed to interface other devices to the MCP since you won't need to add inverter logic chips to get the correct signal polarity into the MCP It is also very handy for getting the signals the right way up e.

Using the MCP you could invert that input and test for a 1 in my mind a key press is more equivalent to an on state i. Using this device would allow you to correct this easily. If you have a design that has critical interrupt code e.Pages: [1] 2. I have been playing around with one of these and looking at a number of examples of setting up interrupts.

From the examples I am getting the impression that the only way they will work is to pull the input pin high by an external pull-up resistor or the internal ones and then pulling the pin low to generate the interrupt. Is that correct or is it also possible to pull the input pin low and generate the interrupt by taking it high?

Is your query about interrupts on the Arduino or the MCP?

Interrupts, Interrupts everywhere! Make any Pin an Interrupt Pin on your Arduino - Tutorial

Please do not send me PMs asking for help. Post in the forum then everyone will benefit from seeing the questions and answers. Are you referring to the MCP? In the datasheet there is an INTPOL interrupt polarity bit which configures if an interrupt is active high or active low.

Please post technical questions on the forum, not by personal message. Quote from: Nick Gammon on Jan 22,am. This interrupt example from the Adafruit MCP library does not seem to work for me. It wont generate interrupts on the arduino and the LED pin does not flash.

Has any one tried it and gotten it to work on their breadboard? Code: [Select]. According to the datasheet: Quote. I have some test code below which tests interrupts on the MCP I just checked and it works fine: Code: [Select].

MCP interrupts and arduino sorry for re-posting - can't find my original. These MCP interrupts just don't make sense. The loop function then resets those flags and turns off the appropriate dp and attached LED - causing a different color flash according to which ISR was triggered from the MCP. However if I disconnect either one of the wires connecting the MCP int pins from the nano then touching both mcp portA 0 and mcp portA 1 with a wire connected to 5V both cause nano int0 to trigger or both cause nano int1 to trigger.

In other words the mcp int pins still seemed to be in mirror mode despite this: mcp. In order to trigger it gain I have to reset the arduino. Digital pin 6 on the nano is connected to the rest pin of the mcp so that I can manually reset it in code so that I could continually trigger interrupts with the interrupt example that came with the library - it seemed to work, but not with my code below.Accepting essential orders - here's how.

Please be positive and constructive with your questions and comments. My problem is that the device does not report interrupts initially or after a power cycle or hitting the reset button on the arduino. Toggling the reset doesn't seem to help and the only thing that does work is unpluging and reconnecting the interrupt connection.

mcp23017 interrupt example

I couldn't get a good picture, but I'm consistent with the attached image except I'm not using the resistors as they were not suggested in the Adafruit tutorial. Should I be pulling the I2C lines high? I would have tried, but I'm low on resistors at the moment. I get the correct number of flashes for the most part, although I seem to pick up a few of the "impossible" conditions when disconnecting the pins as well. I also feel that I'm not getting consistent results when I modify the sketch, for example when I modify the mcp interrupt pins in my sketch, sometimes the old interrupts are still triggered after reprogramming.

Any ideas? I've tried to start with the most basic example of what I want to accomplish, but I'm not getting the expected results. I did try to ask this question in another post, but I'm not sure it was noticed: viewtopic.

Re: MCP power cycle, no interrupt by dustinthurston on Fri Feb 20, pm I'm using the example sketch below. The resistor values aren't critical. Anything from about ohms to 47k should work. All you need is something to pull the lines high when nobody is pulling them low. If the I2C communication isn't working at the signal level, it might be interfering with the reads that should clear the interrupt registers. Re: MCP power cycle, no interrupt by dustinthurston on Sat Feb 21, pm I added the pullup resistors, but had the same results.

I also moved the setup to a pro mini and had the same results. So, it seemed I was picking up some sort of initial interrupt that was not being read. I tried cleanInterrupts first, it didn't help.

The others solved my problem. I'm not clear on why the arduino interrupt function is not triggered by the initial low. Also, since I had such a difficult time with the example on multiple boards, I would say this is a bug that should be corrected in the github example, unless something is wrong with the chip I received.

It turns out it was pulling mA. I was able to further track down the current draw to the reset pin, so It seems I do have a hardware issue. Post a photo of your hardware and connections and we'll see if that gives us any clues.

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Re: MCP power cycle, no interrupt by dustinthurston on Mon Feb 23, am I'm capturing the current draw here. I also confirmed that the current is exiting through the Vss pin. You do not have the required permissions to view the files attached to this post. That provides a secondary current path, and if you have a 5v supply with a 3.

Re: MCP power cycle, no interrupt by dustinthurston on Mon Feb 23, am Same results with blue wire removed. Also same with communication lines removed as well.

I am using an 8mhz 3. I'm sure there's a good chance I wired something wrong at some point as I was troubleshooting my initial problems. Other than the current draw and getting hot, it seems to be working correctly as long as I initially read the interrupt. Try putting a 10k between the reset pin and VCC.

Adding an MCP23017 I/O Extender to Arduino or ESP8266

That will limit the current to a level that shouldn't cause any heating.None of the ones I could find actually implement interrupts via the chip Polling is not ideal for my home monitoring setup. I was already monitoring via interrupts and the onboard GPIO pins using the awesome RPIO module and wanted to continue using interrupts with the expansion chip. You can find the library on my BitBucket. I purchased mine on eBay from a US seller but they are available from several resellers.

If you have multiple I2C devices, you will need to solder the jumpers on the bottom of the board to change the address — details are at the assembly instructions link above. Now, to use interrupts from the expander, you need to use at least one of the onboard Pi GPIO pins to monitor for when an interrupt occurs.

Note, you really need to use a resistor to keep the current flow between the two ports low to avoid damage — 10 or 12K will work fine. Interrupt port mirroring means that if an interrupt appears on any of the 16 ports, both INT ports will trigger at the same time.

I have several functioning examples for using this chip the examples directory on BitBucket:. That is it! I hope others find this useful. If you have improvements or bug fixes, please submit a pull request! Dan, I am very excited about trying out your code, but am having trouble with the installation. I am using Pi 2, gcc version 4.

The file i2c-dev. Hi Clint! What you actually need to do is copy this file:. Hi there I seem to have all libraries etc. Is I2C setup and working? Is the chip showing connected when you run i2cdetect per the Adafruit guide above? However when I run: print bus. The default busnum in the AdafruitI2C class is set to -1 and for some reason it fails to get the correct busnum when initialising.

Oh interesting. In the meantime blinky and basicinput work fine but when I run interrupttest I get the following:.For SPI usage on the Photon you want the connection setup as described here.

mcp23017 interrupt example

I suggest you rewire your project as follows. I do not understand how the pins are numbered though. I have previously used the i2c version of this chip where I would write to a register a decimal value which would enable a certain bit pattern.

I understand how this works. Thanks for pointing me in the right direction.

How to connect I2C 16-bit Port Expander to your Raspberry Pi working under Windows IOT Core

Does this mean your setup works now? The reason I ask is that it seems as if you were powering the setup from the TX pin of the Photon - is this intended, or did you not want the red wires at the bottom of your pic attached to Vin?

Start with the pin nearest to the dot or groove on the chip with 1 count along side change over to the other side and count up again. The pins on the 23S17 are numbered using the small circle indent that references pin 1.

Then they go up the right side, around the top and down the other side. So across the chip from pin 1 is pin PIN 1. Here is the data sheet. Photo angle makes it look like that. I used red for GND as i had more of them on hand than the black ones. The class actually changes the way the pins are numbered according to here. I have not studied the code yet but i will do so shortly to understand why this does not work.

Thank you mtnscott. I was referring to the way the the library changes GPA0 at pin 21 to 1. The library on build is quite different from the arduino library. A quick read through the src file and the datasheet solved the confusion.

For that relationship you need to consult the datasheets. But i am trying to make them work using a single slave select using different addresses. However on setting the address to 1 i do not get any response from the chip. Aliyou cannot use a single slave select since the MISO lines from each device will clash as both will no longer be in tri-state mode.

You MUST use separate select lines. Alithis is defined in the SPI specification.

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In short, I2C is a 2-wire bus which can address up to devices each with a unique address whereas SPI is a 4-wire typically bus with no addressing and only single device actively communicating at a time. Got it! The MCP23S17 should work in a similar fashion right? Attach the INT pin on the chip to one of the pins on the photon and call attachinterrups.

When i push the button D7 lights up once. I cannot seems to get interrupts to trigger again. But it does not seem to be working.Forums New posts Search forums. What's new New posts Latest activity.

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Search forums. Log in. For a better experience, please enable JavaScript in your browser before proceeding. MCP i2c IO expander data. Thread starter westaust55 Start date May 24, I took the opportunity to create yet another table Attached is a one-page table listing all the MCP registers, with notes on the functions and details on the each bit in control registers.

MCP Control Map. Last edited: Jan 11, You are a legend Westy. I have just received some freebies from Microchip. These IC's are fantastic. I am still coming to grips with the input interrupts, will post some results on this thread after I wade through it. PerthEng Member. Any sources for these chips local to WA?

Last I bought were in DIP format. I have used them as inputs before- I especially like the pull up resistors which means you don't need current limiting on the inputs like you do with a raw picaxe chip. I have also used the surface mount versions with great success. I but them direct from microchip - they arrive in Australia in a few days from Thailand on Fedex.

I'm sure i have code somewhere, im in the process of moving but I'll see if i can find it MCP - Demo using interrupt signals to read inputs alphamike27, Here is some code that I have put together as a demo for a trial on monitoring for an interrupt signal with the PICAXE and then collecting the data from portA indicating which input was activated and flashing an output on portB to indicate the signal was handled. Simulation looks okay but yet to wire up a circuit.

Will let you know how it all goes and then add a final working version to the code snippet area. Attached is an updated version which also has the device address given at the top for quick reference. MCP Control Map rev1. I tried read my MCP ports.The data for each input or output is kept in the corresponding input or output register. The polarity of the Input Port register can be inverted with the Polarity Inversion register.

All registers can be read by the system master. The interrupt output can be configured to activate under two conditions mutually exclusive : 1. When any input state differs from its corresponding Input Port register state. This is used to indicate to the system master that an input state has changed. The Interrupt Capture register captures port values at the time of the interrupt, thereby saving the condition that caused the interrupt.

The Power-on Reset POR sets the registers to their default values and initializes the device state machine. The hardware address pins are used to determine the device address.

The system demonstrates the simplicity of monitoring four pins configured as inputs and applying a predetermined pattern on LEDs connected to the remaining 12 pins configured as outputs. For pricing and availability, contact Microchip Local Sales. Sampling Options Buy Now. Development Environment. Similar Devices. Additional Features.

mcp23017 interrupt example

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