BACtrack S80 Specifikace stáhnout pdf (Strana 110)

107

4.3.1 Display Functions

In order to communicate over the I2C bus with the display, an accurate “bit-

banged” I2C interface was created using a set of functions to encapsulate certain

functionality of the bus, including operations to drive pins high and low, convert

strings to binary output, transmit, receive acknowledgement, and configure the

LCD to default functionality. Table 4.3.1-1 describes the purpose of each function

in the display software.

Function

Description

void I2C_Init()

Prepares the I2C bus data structure, Initializes

GPIO pins to SDA and SCL

void I2C_Start()

Creates a START condition on the I2C data

line by creating a falling edge on SDA, while

holding SCL high

void I2C_Stop()

Creates a STOP condition on the I2C data line

by creating a rising edge on SDA, while

holding SCL high

void I2C_WriteByte(byte)

Writes a single byte to the I2C bus by masking

each bit to determine the value (1 or 0),

creating the correct high/low transition on SDA,

then driving the clock line high and low to clock

the data in

void I2C_GetAck()

Sets the SDA line to input and drives the SCL

line high. Checks if the device pulls the SDA

line low to acknowledge receipt of a packet.

void SetPinValue(Port, Pin, bool)

Sets an individual pin to either high or low

bool GetPinValue(Port, Pin)

Gets the value of an individual pin

void SetPortValue(Port, byte)

Sets lines of a port to either output or input,

depending on the input 8-bit value

char GetPortValue(Port)

Returns the current 8-bit register controlling the

port direction

void Init_LCD()

Initializes the LCD for output using values

suggested by the manufacturer

void cgram()

Part of the LCD initialization, this routine writes

values to the internal LCD character RAM, as

suggested by the manufacturer

void show(char *text)

Loops through an input string array, outputting

each character to the LCD display

void nextline()

Moves cursor to the next line of the LCD

void clearscreen()

Clears the LCD screen

Table 4.3.1-1 – Display Communications Functional Breakdown

1 2 ... 105 106 107 108 109 110 111 112 113 114 115 ... 147 148

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