Using the same strategy as before, we look for the command we’re interested in on the datasheet. Let’s read the data we wrote to our EEPROM armed with nothing more than the datasheet and the I2C protocol. It’s been a daunting few weeks, but we’re finally there.
From there, we learned how the data stored in these variables is passed along through to functions and what an array really is. Before learning to read from that EEPROM, which we will do today, we needed to gain the prerequisite knowledge of how data is stored in memory and how pointers work. In that post, we learned to write to an external EEPROM over the I2C protocol using nothing more than a datasheet and the Arduino’s built-in Wire library. write(0x00) // begin here Wire.We first began our journey into learning the I2C protocol three weeks ago. write(0x00) // DDR Port0 all output Wire. beginTransmission(0x20) // setup out direction registers Wire. #include // specify use of Wire.h library. There are eight resistor/LED indicators on pins 21 - 28. As it is below all LEDs on Port0 will come on only when corresponding switch on Port1 is closed. In program two below all the LEDs on Port0 will be on, will go off when switch is closed. When the eight switches are open (see schematic) the normal input to Port1 pins are all "0". nd(0xFF) // DDR invert input polarity port1 0xFF = B11111111 Wire.begin() // connect the Arduino as a master, setup data direction What if I wanted both ports to be inputs, but invert the input polarity (a 1 becomes a 0) on Port1 where my switches are connected? Wire.beginTransmission(0x20) // setup out direction registers
Wire.begin() // connect the Arduino as a master In the setup sections of the two sample programs the MCP23016 is setup as follows to make Port0 all output and Port1 all inputs by writing to the two I/O direction registers: This allows eight individual devices to be connected at one time with individual addresses of 0x20 through 0x27. It has additional three-bit address pins A0, A1, A2 on pins 16, 17, and 18 respectively. The MCP23016 I/O expander is an I2C slave device with a base address of 0x20. See Using Hardware Interrupts ATMEGA168/ArduinoĠx0B I/O control register 1 (same thing as 0x0A)Ī one-bit register that controls the sampling frequency of the 2 I/O ports.Ī "0" results in a 32 millisecond sample rate.Ī "1" results in a 200 microsecond sample rate, but uses more power in standby. These are read only, shows state of port during an interrupt.Ĭonnect an LED/resistor to VCC (+5 volts) and to pin 6 of 1 = output, 0 = input.Ġx07 I/O direction register Port1 bit addressable. 1 invert bit, 0 no invert.Ġx06 I/O direction register Port0 bit addressable. 1 invert bit, 0 no invert.Ġx05 Invert input polarity Port1 bit addressable. Write won't work if bit/port set for input.Ġx04 Invert input polarity Port0 bit addressable. The MCP23016 has 12 general purpose registers as follows:Ġx00 Port0 can be directly written/read.Ġx01 Port1 can be directly written/read.Ġx02 Output latch 0 write changes output Port0.Ġx03 Output latch 1 write changes output Port1. Polarity inversion register to configure the polarity of the input port data. Open-drain interrupt output pin (6) on input change and interrupt port capture register. High-current drive capability per I/O: source/sink 25 milliamps. Three hardware address pins (A0-A2 pins 16-18) can address up to eight devices at one time. Two separate 8-bit I/O ports bit programmable. Using the ATMEGA168/Arduino with a Ds1307 Real Time ClockĪlso MCP23016 I2C I/O Expander spec sheet.
ARDUINO I2C EEPROM PROGRAMMER SERIAL
Note that in this discussion I'll use hex numbers, a digital "1" is five volts and a digital "0" is zero volts.
ARDUINO I2C EEPROM PROGRAMMER HOW TO
Here we will explore how to use the MCP23016 with the ATMEGA168/Arduino. It provides 16 individually programmable I/O pins that can source/sink 25 milliamps per pin up to about 250 milliamps total. The MCP23016 is a popular I/O expander integrated circuit manufactured by Microchip.
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