The loop function start with the creation of an empty string. Now the humidity and temperature is read from the DHT sensor and also the current time in unix datetime format from the RTC. After we have all values that we want to save to the SD card we create one string that will be one line in the text file that we create on the SD card. Therefore we connect all measurements and separate them with a comma. The next step is to write the complete string to the SD card. Therefore we open the text file with the open function of the SD library and set the path to the text file and use the argument FILE_WRITE to open the file with writing permission. If the file is available we write the dataString to the opened text file and close the file. To see the string in the serial monitor of the Arduino IDE, we write the same string to the serial USB connection. If we can not open the file, we write an error message and at the end of the script we wait for 2 seconds. # include 'FS.h' # include 'SD.h' # include 'SPI.h' # include 'RTClib.h' # include 'DHT.Low level initialization of the MCP23017 IO expander.The 16-bit I/O port functionally consists of two 8-bit ports (PORTA and PORTB). For the LED bar circuit, we will blink the LEDs with blink without delay, using the millis() function. MCP23017 uses high speed I 2 C interface while MCP23S17 used high speed SPI interface.

This development board communicate to the microcontroller using I2C interface and increases the number of input-output pins of microcontroller.

Both “byte writes” and “sequential writes” are As I’m using I2C I only need four connections: VCC, GND, SCL and SDA (I could have left off the other You have to add this declaration in your device configuration file if you like to use also BeforeWriteOutputs method: I haven't deep dived in the MCP23017 device datasheet yet. Once configured, you can use any of the 16 pins as pins for your projects. The operation is ended with a Stop (P) or Restart (SR) condition being generated by the master. In above code,i used i2c for eeprom interfacing and mcp23017 io expander.Essentially, you have a set of ‘row enable’ DO pins, and only one is

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