Difference between revisions of "Embedded System Tutorial GPIO"
From Embedded Systems Learning Academy
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Revision as of 21:49, 19 July 2013
Contents
Objective
Interface your LPC17xx to a switch and an LED.
Although the interface may seem simple, you do need to consider hardware design and know some of the fundamental of electricity. There are a couple of goals for us :
- No hardware damage if faulty software is written.
- Circuit should prevent excess amount of current to avoid processor damage.
Required Background
- You should know how to bit-mask variables
- You should know how to wire-wrap
- You should know fundamentals of electricity and the famous V = IR equation.
Lecture
Hardware Registers
The hardware registers map to physical pins. If we want to attach our switch and the LED to our microcontroller's PORT0, then here are the relevant registers and their functionality :
| LPC_GPIO0->FIODIR | Direction of the port pins, 1 = output |
| LPC_GPIO0->FIOPIN |
Read : Sensed inputs of the port pins, 1 = HIGH Write : Control voltage level of the pin, 1 = 3.3v |
| LPC_GPIO0->FIOSET | Write only : Any bits written 1 are OR'd with FIOPIN |
| LPC_GPIO0->FIOCLR | Write only : Any bits written 1 are AND'd with FIOPIN |
Switch Design
LED Design
Conclusion
At the end of this lab, you should be familiar with how a microcontroller's memory can access physical pins.
