CP316: Microprocessor Systems and Interfacing
Introduction to the QwikFlash Development Board
When learning a new high level language, the typical first program is a 'Hello
world' program. When using a new development board, the typical first program
is one that turns LED(s) on/off. LEDs are usually connected to bi-directional
I/O ports (also known as parallel ports) and these are the simplest peripheral
interface on any board.
- introduction to the development board LEDs
- location of the bi-directional I/O port A
- On the QwikFlash board, the power LED has a specific function that was
covered in first week's lab. The power LED is not under programmer control.
The QwikFlash board has four programmer accessible LEDs which have been named:
Alive LED, Left LED, Center LED, and Right LED. On the QwikFlash board schematic,
locate these LEDs. Sketch the LED circuits in your lab notebook and record
any component values. Locate all components on the physical board.
- Which microcontroller pins (give pin numbers from schematic) are used to
connect to these four LED circuits? How are these pins labeled on the silk
artwork on the board?
- How is the circuit of the alive LED different from the other three LEDs?
- How is this difference related to the difference in pin RA4? In the datasheet,
see Table 9-1 PORTA Functions. In the reference manual, see section 11.16
Design Tips, answer 2, part 3 for a more detailed explanation.
- General purpose I/O pins are the simplest peripheral devices and are generally
called 'ports'. Note that all of the programmable LEDs are connected to PORTA.
Port pins may have more than one function; this is called "multiplexing" as
the primary function of the pin is multiplexed with alternate functions.
On a datasheet, these functions are specified as function 1 / function 2 /.../
function n. The actual pin function for a specific development board
is determined by the physical circuitry attached to the pin. If no circuitry
is connected to a pin, any of the functions are possible and will be determined
when a circuit is attached to the pin. From datasheet Table 9-1 PORTA
Functions, note all of the functions for each RAn pin (n = 0, 1, ..,
5). From the QwikFlash board schematic, note the function that has been implemented
for each of these pins.
Demonstration - explain the components involved in the LED circuitry and
their location in the schematic and the physical board.
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