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| en:multiasm:exercisesbook:avr:sut [2026/04/30 16:52] – [Communication] pczekalski | en:multiasm:exercisesbook:avr:sut [2026/05/04 14:50] (current) – [Visualising Instruction Execution Time Using an Oscilloscope] pczekalski |
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| <note tip>Nodes are interconnected in pairs: 1-2, 3-4, 5-6, 7-8, 9-10. Scenarios for data transmission between MCUs require booking and the use of correct nodes for sending and receiving messages.</note> | <note tip>Nodes are interconnected in pairs: 1-2, 3-4, 5-6, 7-8, 9-10. Scenarios for data transmission between MCUs require booking and the use of correct nodes for sending and receiving messages.</note> |
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| ===== Laboratory Scenarios ===== | ==== Visualising Instruction Execution Time Using an Oscilloscope ==== |
| Below are hands-on lab scenarios intended for use with the [[https://iot.aei.polsl.pl|VREL NextGen system]] (access via a browser; no need to install the toolchain or any other software). | Let's try to visualise how code operates the GPIO. Naturally, in the remote lab, it is not possible to do it remotely, so here we present some desk-based experiments.\\ |
| | The ''LAT_PIN'' is GPIO4, and an oscilloscope is connected to it. |
| | In the function that displays a single digit, there is a section that loads a binary mask into the internal registers, enabling the LED segments that constitute the digit to be turned on and off. It is: |
| | <code asm> |
| | ... |
| | sbi LAT_PORT, LAT_PIN |
| | cbi LAT_PORT, LAT_PIN |
| | ... |
| | </code> |
| |
| * | The figures {{ref>arduinounodigitoscilloscope1}} and {{ref>arduinounodigitoscilloscope2}} present the ''LAT_PIN'' signal, called periodically during the display of the consecutive digits (they represent the same signal but differ by the oscilloscope time base for better observation).\\ |
| | ''SBI'' causes the signal to rise, while ''CBI'' to fall. Thus, the HIGH time is the exact time during which the CBI instruction executes. It takes about 120-130ns.\\ |
| | The Arduino Uno operates at 16 MHz, so each cycle is 1/16000000 s, which is about 63 ns. According to the documentation, ''CBI'' takes 2 cycles, which is ~126ns. |
| |
| | <figure arduinounodigitoscilloscope1> |
| | {{:en:multiasm:exercisesbook:avr:pic_1054.png?300|}} |
| | <caption>''LAT_PIN'' signal (50ns time base)</caption> |
| | </figure> |
| |
| | <figure arduinounodigitoscilloscope2> |
| | {{:en:multiasm:exercisesbook:avr:pic_1055.png?300|}} |
| | <caption>''LAT_PIN'' signal (25ns time base)</caption> |
| | </figure> |
