Hi everyone, I would like to share with the community an educational reflection on programming and microcontroller architecture. The Arduino ecosystem is extraordinary because it allows anyone to get a project up and running in minutes, thanks to the abstraction of C++. However, this high level of…

[image] GolamMostafa: The following (Fig-1) line taken from datasheet of 328P Section-6.1 (2015) says that the interrupts have priorities. If so, as I understand, only interrupt of higher priority can interrupt the current interrupt if it is of lower prioity. "All interrupts share the same pr…

[image] GolamMostafa: pinMode(2, INPUT_PULLUP); "I think that this is very confusing for beginners. This is because setting the output to HIGH when DDRB is 0 enables the internal pull-up resistor. Therefore, DDRB decides whether it acts as a pull-up or a standard output. While this process is…

[image] costycnc: Beginners might interpret it as a specific function that explicitly configures a pin with a pull-up Then they would be correct

[image] UKHeliBob: Then they would be correct A beginner looking at it from a software/abstract level would logically ask: 'If I enable the pull-up, and then change the pin to an OUTPUT, where does that resistor go? Is it still there limiting my output current?'

They may well ask that question, but they would still be correct in interpreting pinMode(2, INPUT_PULLUP); as a function that configures a pin with a pull-up. Suppose that they use assembler to set a pin to INPUT_PULLUP then change the pin to an OUTPUT. Where does the resistor go ?

[image] UKHeliBob: Suppose that they use assembler to set a pin to INPUT_PULLUP then change the pin to an OUTPUT. Where does the resistor go ? Remember? [image] [image] [Education] Demystifying Microcontroller PORTB: Using ATmega328P and Assembly to Understand Registers This is the famo…

I remember it but don't think that it is necessary A question : When you use DDRB to set the direction of the pin to OUTPUT does it matter that the pin is still connected to 5V via the pullup resistor when the pin was previously INPUT_PULLUP ?

[image] GolamMostafa: If lower priority interrupt can suspend the higher priority interrupt, then my question to Microchip, what is the significance of assigning priorities to the interrupts in 328P? Think of it this way: There is only two priority levels of running code: "interruptible" and …

[image] costycnc: I think that this is very confusing for beginners. I dare say we have more experience with beginners and some who don't even qualify yet as beginners. Your ideas may work for some. I think that registers and pins and machine code numbers, circuit diagrams of output ports &c…

[image] alto777: Your ideas may work for some. I think that registers and pins and machine code numbers, circuit diagrams of output ports &c. is waaay easierto take on than two or three lines of C. For example: byte y1 = 0x35; The above C++ code does not say at all that the data transfer pr…

[Education] Demystifying Microcontrollers: Using ATmega328P and Assembly to Understand Registers

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costycnc July 25, 2026, 8:12pm 1475

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