63 lines
1.4 KiB
Markdown
Executable File
63 lines
1.4 KiB
Markdown
Executable File
# Intro to Embedded Systems Lecture Notes: January 31st, 2023
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## POLLING
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**Initialize the port**
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Output:
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```c
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P6DIR |= BIT6;
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P6OUT &= ~BIT6;
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```
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Input:
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```c
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P4DIR &= ~BIT1;
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```
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Clear LOCKLPM5 (Lock low-power mode) from PMCTL0 (Power management control):
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```c
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PMCTL0 &= ~LOCKLPM5;
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```
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Program the board
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**Floating condition: not 1 or 0**
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Fix using pull-up/pull-down resistor
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## PULL-UP / PULL-DOWN RESISTORS
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**Pull-up resesistor**
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- Active Low
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- Mostly preferrable for MCUs
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- Safety -> reduces noise
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**Pull-down resistor**
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- Active high
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## I/O Configuration
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| P<sub>x</sub>DIR | P<sub>x</sub>REN | P<sub>x</sub>OUT | Comment |
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|-------|-------|-------|----------------|
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| 0 | 0 | X | Input |
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| 0 | 1 | 0 | Input with PDR |
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| 0 | 1 | 1 | Input with PUR |
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| 1 | X | X | Output |
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## LOW POWER MODE
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| SCG<sub>1 | SCG<sub>0 | OSC OFF | CPU OFF | Mode |
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|------|------|---------|---------|----------|
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| 0 | 0 | 0 | 0 | Active |
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| 0 | 0 | 0 | 1 | LPM0 |
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| 0 | 1 | 0 | 1 | LPM1 |
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| 1 | 0 | 0 | 1 | LPM2 |
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| 1 | 1 | 0 | 1 | LPM3 |
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| 1 | 1 | 1 | 1 | LPM4 |
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## WHEN INTERRUPT HAPPENS
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- Processor stops what it's doing
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- Stores information to later resume
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- Executes interrupt service routine (ISR)
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- Restores saved information
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- Resumes execution
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