1. Matrix keyboard
1. The method of detecting the button:
(1) First, assign all 1-4 to a low level, and 5-8 to a high level. When a button is pressed, there will be a point in 5-8 that will be pulled low.
(2) Then set one position in 1-4 to 0 and other positions to 1 in turn, and observe the corresponding return value to determine which button is pressed.
2. Corresponding program
unsigned char bsp_mkeyscan()
{
unsigned char keyvalue = 0x99;
KEYPORT = 0xF0;
if (KEYPORT != 0xF0)
{
KEYPORT = 0xFE;
if (KEYPORT != 0xFE)
{
keyvalue = KEYPORT;
while(keyvalue == KEYPORT)bsp_segb();;
}
KEYPORT = 0xFD;
if (KEYPORT != 0xFD)
{
keyvalue = KEYPORT;
while(keyvalue == KEYPORT)bsp_segb();;
}
KEYPORT = 0xFB;
if (KEYPORT != 0xFB)
{
keyvalue = KEYPORT;
while(keyvalue == KEYPORT)bsp_segb();;
}
KEYPORT = 0xF7;
if (KEYPORT != 0xF7)
{
keyvalue = KEYPORT;
while(keyvalue == KEYPORT)bsp_segb();;
}
}
return keyvalue; //根据keyvalue的值即可以确定按下的键
}2. LCD1602
1. LCD principle
LCD (Liquid Crystal Display): the abbreviation of liquid crystal display, a passive display, that is, the liquid crystal itself does not emit light, but after the liquid crystal is processed, it can change the characteristics of the light passing direction, and achieve black characters on a white background or white characters on a black background. displayed purpose.
Liquid crystal displays have the advantages of low power consumption and strong anti-interference ability, and are widely used in instrumentation and control systems.
2. LCD classification
According to the arrangement shape, it is divided into: field type, dot matrix character type and dot matrix graphic.
Field types
are widely used in spreadsheets, digital meters, and calculators.
The dot matrix character type
displays letters, numbers and symbols. It is composed of 5 × 7 or 5 × 4 lattices and is widely used in single-chip microcomputer application systems.
In devices such as dot-matrix graphics
notebook computers and color TVs.
1602 LCD is also called 1602 character LCD. It is a dot matrix LCD module specially used to display letters, numbers, symbols, etc. It consists of several 5X7 or 5X11 dot matrix character bits, each dot matrix character bit can be displayed a character. There is a dot space between each bit, and there are also spaces between each line, which play the role of character spacing and line spacing.
1602LCD means that the displayed content is 16X2, that is, it can display two lines, each line of 16 characters LCD module.
3. Pins of LCD1602
Ground pin 1
The second pin is connected to the 5V positive power supply
The 3rd pin VL is the contrast adjustment terminal of the liquid crystal display. The contrast is the weakest when connected to a positive power supply, and the highest when the contrast is grounded. When the contrast is too high, a "ghost image" will be produced. The contrast can be adjusted by a 10K potentiometer during use.
Pin 4: RS is the register selection, select the data register when the high level, select the instruction register when the low level.
第5脚：R/W为读写信号线，高电平时进行读操作，低电平时进行写操作。当RS和R/W共同为低电平时可以写入指令或者显示地址，当RS为低电平R/W为高电平时可以读忙信号，当RS为高电平R/W为低电平时可以写入数据。
第6脚：E端为使能端，当E端由高电平跳变成低电平时，液晶模块执行命令。
第7～14脚：D0～D7为8位双向数据线。
第15脚：背光源正极。
第16脚：背光源负极。
4、显示地址映射
第一行第一个的地址是：80H
第二行第一个的地址是：C0H
5、字符发生存储器
在对液晶模块的初始化中要先设置其显示模式，在液晶模块显示字符时光标是自动右移的，无需人工干预。每次输入指令前都要判断液晶模块是否处于忙的状态。
指令3：光标和显示模式设置 I/D：光标移动方向，高电平右移，低电平左移S：屏幕上所有文字是否左移或者右移。高电平表示有效，低电平则无效
指令4：显示开关控制。 D：控制整体显示的开与关，高电平表示开显示，低电平表示关显示； C：控制光标的开与关，高电平表示有光标，低电平表示无光标；B：控制光标是否闪烁，高电平闪烁，低电平不闪烁。
指令5：光标或显示移位 S/C：高电平时移动显示的文字，低电平时移动光标。
指令7：字符发生器RAM地址设置。
指令8：DDRAM地址设置。
指令9：读忙信号和光标地址 BF：为忙标志位，高电平表示忙，此时模块不能接收命令或者数据，如果为低电平表示不忙。
指令10：写数据。
指令11：读数据。
写指令38H（不检测忙信号）
延时5mS
写指令38H（不检测忙信号）
延时5mS
写指令38H（不检测忙信号）
以后每次写指令、读/写数据操作均需要检测忙信号
写指令38H：显示模式设置
写指令08H：显示开
写指令01H：清屏
写指令06H：显示光标移动设置
写指令0CH：显示开及光标设置