{"id":814,"date":"2020-10-30T20:56:26","date_gmt":"2020-10-30T13:56:26","guid":{"rendered":"https:\/\/www.makeriot2020.com\/?p=814"},"modified":"2022-05-28T15:08:34","modified_gmt":"2022-05-28T08:08:34","slug":"mcp23017-with-adafruit-library","status":"publish","type":"post","link":"https:\/\/www.makeriot2020.com\/index.php\/2020\/10\/30\/mcp23017-with-adafruit-library\/","title":{"rendered":"MCP23017 with Adafruit Library"},"content":{"rendered":"\n

In a previous post<\/a>, I have shown you how to use the MCP23017 16 Port I2C I\/O Port extender with the standard Wire library, as supplied with the Arduino IDE. In this post,
I will have a quick look at using Adafruit’s library for this IC. I believe that this library brings a lot of ease-of-use to the part, making it possible to obscure some of the complexity of I2C.

I do however prefer to use the native Wire library myself, as it is slightly faster.

You can download the Adafruit MCP23017 Library from here<\/a>..

<\/p>\n\n\n\n

Pin Addressing<\/h1>\n\n\n\n

When using single pin operations such as pinMode(pinId, dir)<\/em> or digitalRead(pinId)<\/em> or digitalWrite(pinId, val)<\/em> then the pins are addressed using the ID’s below. For example, for set the mode of GPB0<\/em> then use pinMode(8, …)<\/em>.<\/p>\n\n\n\n

Physical Pin #<\/th>Pin Name<\/th>Pin ID<\/th><\/tr><\/thead>
21<\/td>GPA0<\/td>0<\/td><\/tr>
22<\/td>GPA1<\/td>1<\/td><\/tr>
23<\/td>GPA2<\/td>2<\/td><\/tr>
24<\/td>GPA3<\/td>3<\/td><\/tr>
25<\/td>GPA4<\/td>4<\/td><\/tr>
26<\/td>GPA5<\/td>5<\/td><\/tr>
27<\/td>GPA6<\/td>6<\/td><\/tr>
28<\/td>GPA7<\/td>7<\/td><\/tr>
1<\/td>GPB0<\/td>8<\/td><\/tr>
2<\/td>GPB1<\/td>9<\/td><\/tr>
3<\/td>GPB2<\/td>10<\/td><\/tr>
4<\/td>GPB3<\/td>11<\/td><\/tr>
5<\/td>GPB4<\/td>12<\/td><\/tr>
6<\/td>GPB5<\/td>13<\/td><\/tr>
7<\/td>GPB6<\/td>14<\/td><\/tr>
8<\/td>GPB7<\/td>15<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Some examples<\/strong>, directly from the library, all code belongs to Adafruit, and was not written by me.

1. A Button Example<\/p>\n\n\n\n

\n
#include <Wire.h>\n#include \"Adafruit_MCP23017.h\"\n\n\/\/ Basic pin reading and pullup test for the MCP23017 I\/O expander\n\/\/ public domain!\n\n\/\/ Connect pin #12 of the expander to Analog 5 (i2c clock)\n\/\/ Connect pin #13 of the expander to Analog 4 (i2c data)\n\/\/ Connect pins #15, 16 and 17 of the expander to ground (address selection)\n\/\/ Connect pin #9 of the expander to 5V (power)\n\/\/ Connect pin #10 of the expander to ground (common ground)\n\/\/ Connect pin #18 through a ~10kohm resistor to 5V (reset pin, active low)\n\n\/\/ Input #0 is on pin 21 so connect a button or switch from there to ground\n\nAdafruit_MCP23017 mcp;\n  \nvoid setup() {  \n  mcp.begin();      \/\/ use default address 0\n\n  mcp.pinMode(0, INPUT);\n  mcp.pullUp(0, HIGH);  \/\/ turn on a 100K pullup internally\n\n  pinMode(13, OUTPUT);  \/\/ use the p13 LED as debugging\n}\n\n\n\nvoid loop() {\n  \/\/ The LED will 'echo' the button\n  digitalWrite(13, mcp.digitalRead(0));\n}<\/code><\/pre>\n<\/div><\/div>\n\n\n\n
2. An Interrupt Example<\/p>\n\n\n\n
\n
\/\/ Install the LowPower library for optional sleeping support.\n\/\/ See loop() function comments for details on usage.\n\/\/#include <LowPower.h>\n\n#include <Wire.h>\n#include <Adafruit_MCP23017.h>\n\nAdafruit_MCP23017 mcp;\n\nbyte ledPin=13;\n\n\/\/ Interrupts from the MCP will be handled by this PIN\nbyte arduinoIntPin=3;\n\n\/\/ ... and this interrupt vector\nbyte arduinoInterrupt=1;\n\nvolatile boolean awakenByInterrupt = false;\n\n\/\/ Two pins at the MCP (Ports A\/B where some buttons have been setup.)\n\/\/ Buttons connect the pin to grond, and pins are pulled up.\nbyte mcpPinA=7;\nbyte mcpPinB=15;\n\nvoid setup(){\n\n  Serial.begin(9600);\n  Serial.println(\"MCP23007 Interrupt Test\");\n\n  pinMode(arduinoIntPin,INPUT);\n\n  mcp.begin();      \/\/ use default address 0\n  \n  \/\/ We mirror INTA and INTB, so that only one line is required between MCP and Arduino for int reporting\n  \/\/ The INTA\/B will not be Floating \n  \/\/ INTs will be signaled with a LOW\n  mcp.setupInterrupts(true,false,LOW);\n\n  \/\/ configuration for a button on port A\n  \/\/ interrupt will triger when the pin is taken to ground by a pushbutton\n  mcp.pinMode(mcpPinA, INPUT);\n  mcp.pullUp(mcpPinA, HIGH);  \/\/ turn on a 100K pullup internally\n  mcp.setupInterruptPin(mcpPinA,FALLING); \n\n  \/\/ similar, but on port B.\n  mcp.pinMode(mcpPinB, INPUT);\n  mcp.pullUp(mcpPinB, HIGH);  \/\/ turn on a 100K pullup internall\n  mcp.setupInterruptPin(mcpPinB,FALLING);\n\n  \/\/ We will setup a pin for flashing from the int routine\n  pinMode(ledPin, OUTPUT);  \/\/ use the p13 LED as debugging\n  \n}\n\n\/\/ The int handler will just signal that the int has happen\n\/\/ we will do the work from the main loop.\nvoid intCallBack(){\n  awakenByInterrupt=true;\n}\n\nvoid handleInterrupt(){\n  \n  \/\/ Get more information from the MCP from the INT\n  uint8_t pin=mcp.getLastInterruptPin();\n  uint8_t val=mcp.getLastInterruptPinValue();\n  \n  \/\/ We will flash the led 1 or 2 times depending on the PIN that triggered the Interrupt\n  \/\/ 3 and 4 flases are supposed to be impossible conditions... just for debugging.\n  uint8_t flashes=4; \n  if(pin==mcpPinA) flashes=1;\n  if(pin==mcpPinB) flashes=2;\n  if(val!=LOW) flashes=3;\n\n  \/\/ simulate some output associated to this\n  for(int i=0;i<flashes;i++){  \n    delay(100);\n    digitalWrite(ledPin,HIGH);\n    delay(100);\n    digitalWrite(ledPin,LOW);\n  }\n\n  \/\/ we have to wait for the interrupt condition to finish\n  \/\/ otherwise we might go to sleep with an ongoing condition and never wake up again.\n  \/\/ as, an action is required to clear the INT flag, and allow it to trigger again.\n  \/\/ see datasheet for datails.\n  while( ! (mcp.digitalRead(mcpPinB) && mcp.digitalRead(mcpPinA) ));\n  \/\/ and clean queued INT signal\n  cleanInterrupts();\n}\n\n\/\/ handy for interrupts triggered by buttons\n\/\/ normally signal a few due to bouncing issues\nvoid cleanInterrupts(){\n  EIFR=0x01;\n  awakenByInterrupt=false;\n}  \n\n\/**\n * main routine: sleep the arduino, and wake up on Interrups.\n * the LowPower library, or similar is required for sleeping, but sleep is simulated here.\n * It is actually posible to get the MCP to draw only 1uA while in standby as the datasheet claims,\n * however there is no stadndby mode. Its all down to seting up each pin in a way that current does not flow.\n * and you can wait for interrupts while waiting.\n *\/\nvoid loop(){\n  \n  \/\/ enable interrupts before going to sleep\/wait\n  \/\/ And we setup a callback for the arduino INT handler.\n  attachInterrupt(arduinoInterrupt,intCallBack,FALLING);\n  \n  \/\/ Simulate a deep sleep\n  while(!awakenByInterrupt);\n  \/\/ Or sleep the arduino, this lib is great, if you have it.\n  \/\/LowPower.powerDown(SLEEP_1S, ADC_OFF, BOD_OFF);\n  \n  \/\/ disable interrupts while handling them.\n  detachInterrupt(arduinoInterrupt);\n  \n  if(awakenByInterrupt) handleInterrupt();\n}\n\n\nI hope that this shows you another way of using this versatile IC, \nIn a future post, I will show you how to do interrupts, using the native Wire library, as well as point out a few things about why interrrupts sometimes does not seem to be working, as well as a workaround for that.\n<\/code><\/pre>\n<\/div><\/div>\n","protected":false},"excerpt":{"rendered":"
In a previous post, I have shown you how to use the MCP23017 16 Port I2C I\/O Port extender with the standard Wire library, as supplied with the Arduino IDE. In this post,I will have a quick look at using Adafruit’s library for this IC. I believe that this library brings a lot of ease-of-use … Continue reading “MCP23017 with Adafruit Library”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":775,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4,40,51,50,52],"tags":[],"class_list":["post-814","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-arduino","category-esp32","category-i2c-devices","category-io-extender-outputs","category-port-extender-inputs"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t