![]() ![]() The DDR registers are used to set the mode (input or output) for a specific IO pin or a complete port of pins. This means we’ve got the following data direction registers: There are 3 DDR registers in the atmega328p microcontroller, one for each IO port. Now, let’s check how the DDRx, PORTx, and PINx registers are used to manipulate the Arduino ports and pins directly. I’ve also added some labels to ease the demonstration in the next sections hereafter. I tried to break it down into 3 sections for each logical functionality to make it less intimidating for those who are not familiar with digital logic circuits. Here is the hardware block diagram (from the Atmega328p datasheet) that shows you the internal structure and circuitry for 1 IO pin and all the other pins are assumed to have the exact same hardware circuitry. But all in all, this sort of performance optimization comes at a cost of reduced portability and a higher risk of breaking the software especially when you’re using different libraries by other people. However, it can provide significantly faster and better overall control over the IO pins on the Arduino’s microcontroller. There are different ways of accessing port pins as we’ll discuss in the next section.īy direct port manipulation in Arduino, you’re risking breaking things up and you’d be losing the portability aspect of the Arduino platform. Alternatively, we can access only one pin of the PORTD at a time while leaving other pins on the port untouched. ![]() We can set all PORTD pins to be output for example by using the DDRD register and writing to the PORTD register any value we want for the IO pins. And lastly, the PINx register which is the input buffer register that we can use to read the digital status of the port/pin. The PORTx register is used to set (write) the digital output state of the port/pin. The DDRx ( Data Direction Register) is used to set the port/pin mode (data direction) whether a specific pin is going to be an output or input pin. PORT Name Atmega328p Pin Arduino Pin PORTD PD0 D0 PD1 D1 PD2 D2 PD3 D3 PD4 D4 PD5 D5 PD6 D6 PD7 D7 PORTB PB0 D8 PB1 D9 PB2 D10 PB3 D11 PB4 D12 PB5 D13 PORTC PC0 A0 PC1 A1 PC2 A2 PC3 A3 PC4 A4 PC5 A5Įach port on the Atmega328p has 3 registers to control its operation. Note that even the analog input pins can also be used as digital IO pins and they’re mapped to PORTC on the microcontroller. Here is a summarized table for the pin mapping between the Arduino IO pins and the Atmega328p microcontroller. The figure below shows you the Arduino UNO Pinout for all digital IO pins and their mapping to the AVR Atmega328p microcontroller. And there are 3 registers to control each digital IO port which we’ll discuss in the next section.īut for now, let’s check the pin mapping between Arduino IO pins and the Atmega328p microcontroller’s ports and pins. Each port has up to 8 pins numbered from 0 to 7. The Arduino UNO is based on the AVR (Atmega328p) microcontroller which has 3 digital IO ports (PORTB, PORTC, and PORTD). We’ll discuss a lot of code example in this tutorial, so get prepared! Table of Contents Then we’ll test some Arduino port manipulation techniques and assess the speed improvement introduced by doing so.įinally, I’ll give you some macros that implements all Port operations & single-pin operations that you’d ever need in your projects in order to directly access the IO pins in a safe way with minimal risk of breaking other functionalities. We’ll discuss how Arduino IO pins work at a low level and how DDR, PORT, and PIN registers are used to control the operation of IO ports/pins. In this tutorial, you’ll learn Arduino Port Manipulation using Arduino registers access. ![]()
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