A bit shallow on the voice of experience led display

A: LED based display
LED light-emitting devices are commonly used Class 2, and dot matrix digital
1: Digital control
a, 8 digital tube commonly used fonts in general, divided into ABCDEFGP segment, in which P-bit decimal
b, digital tube commonly used 10-pin (units), each a pin, the other two pins for the common, 2 is the Messenger
c, from the size of the points, then many different types of commonly used 0.3 0.5 0.8 1.0 1.2 1.5 1.8 2.3 3.0 4.0 5.0 etc.
d, generally less than 1.0 for single-die, (1.0 a single a double), 1.2 ~ ~ 1.5 for the dual core, 1.8 or more 3 or more die, so their supply voltage requirements are different,
Generally speaking, each related to the core of the pressure drop of about 2.1v, and my experience is the following 5v power supply of 0.8, 1.0 ~ 2.3 12v, 3.0 higher than
e, digital sub-total of yin and yang are two common

2: Dot Matrix
a, lattice used for the 8 * 8, before there are 5 * 8 (now little used)
b, lattice are single die, points (lines) were negative, and (lines) were positive, usually with a 5v power supply
c, 8 * 8 dot matrix for the 16-pin (single color, there are 24, and may be disposed of in two-color dot-matrix or to achieve the same circuit board design monochrome and color are available
, And is also more common) 8 rows eight green, two-color to 24-pin, 8 rows, 8 Red, 8 out green.

Second: the basic principles of display
Divided into static (only digital control can achieve) and dynamic
1: static is better to achieve, in this much talked about

2: The digital dynamic

a, the hardware connection
Digital control is generally 1 / 13 to scan, and then high, then relatively large loss of brightness, as this is assumed to be 13, 16 acts of the line of positive tubes, each row of each segment digital tube connected
Together, each column segment digital tube together in public. Column switches tip127, he can directly drive 154, Darlington 5 amp, pay attention not to increase the output resistance of 127
Line with 595 (164 is not recommended) +2803 or 2003 + a 9013, output in 2003 to add current limiting resistor, typically 56 to 330 ohms (if it is <1.0, the digital control,
Resistance can be directly driven by 595 plus)

b, software

Using 89c51 as cpu, memory can be 24c series, or 28c series, pay attention to their write speed is not fast, but most of the digital input device as
Keyboard or remote control, the speed is sufficient, there are 24c series of relatively slow speed of reading, I found that the data read out each time only about 20 or less will not significantly affect the update
Shown by the clock interrupt 1 interrupt time can not exceed 1.5ms, 1.2ms preferably around, you can read in the interrupt service routine 24c02, can also interrupt the inter-
Gap read, but must be guaranteed to read out a list of all the data! Read out the data into a display area, (in memory define an array buf [16]), in
Off subroutine 595 in the data can be sent, preferably by the serial port, the programming is the simplest.

Send completed, turn off the control line 154, to 595 RCLK (12 feet) of a pulse, the data transmitted from the shift register to latch, then open the 154 and enter the column
Signal can be

3: Dot Matrix

a, lattice generally use 1 / 16 scanning, control theory and digital control almost

b, the hardware: the line with 154 + tip127, the column with 595 plus resistance (0 ~ 56 ohms) direct drive

c, software: the program more, see below

Third: Let us talk about the storage of information
Divided into two kinds,
1: one for the curing of Chinese characters, Chinese character dot-matrix information stored in the 27c256, up to 1024 stored 16 * 16 dot matrix character to be modified only to re-write 27c256, advantage is not lost
Loss, generally we do all this for the bank, he rarely modify the display to accommodate, and each subsequent modifications can be charged (ha ha ~ drawback is not flexible

2: The other is to modify the user, and modify the method is divided into two kinds, early general changes with the keyboard or remote control, so there must be hosted on the Chinese character curing
Library, available 27c040 curing ucdos the hzk16 and asc16 half-width full-width character font, the user input to modify the location you, the user needs to display Chinese characters to the location code
E2POM in a way to save the display when the program up based on location information to the screen to read dot matrix display, there is a common way in recent years is the use of computer
Modify the serial port, there is also divided into two
A, no font control panel, computer sends the information matrix display, control board accepted the information stored in the RAM with battery (also available E2PROM, but the speed
Very slow), this drawback is the battery out of RAM is not reliable and often lose information
B, control panel with a character, the computer sends the machine code of Chinese characters (the code) to the other above

IV: Display control

Send to a lot of information means, in accordance with the different devices and different, and some manufacturers use 374 instead of 595 controls, in that case to write directly to an external port
Then, 374 with means, (if a row of 374 words must turn off the display in the transmission, display of the word, then more brightness, 374 with 2 rows off the display but do not have to increase the hard
Of the cost of), is used less, the 595 is very common. Communication ports can be used to send very simple, you can also simulate the serial port with other ports (port may also at any time since, then
The signal by computer), serial ports can also be used (but I will not ,:)
I used the 595 with 374 +165 to send data, the hardware is more complex, but after a good display of patterns of use! In particular about the shift, extremely happy!
Reminder: the recent discovery by Ssangyong 90S8515 well because he has a SPI port 595 to send the signal Gengshuang! Speed ​​to 3M, (12M transistors) is strongly recommended
We use this chip (by, nor the will to see Double Dragon Awards to the point ....)

Five: Some notes:

1: display time, one per line <1.5MS
2: based on experience, 89C51 12M crystal maximum control 48 16 * 16 lattice, and then large, then the crystal frequency can be improved and optimized procedures (that is, the shortest time to send the program)
3: Comparison of the displayed characters long, must pay attention to the efficiency of the code to send routine, because sending a cycle, so the sooner the better handling of the loop body, we are now
Mostly with the C51, also have to pay attention, I'm the misfortune of.

We see the following example:
if (hangno == 0x10) hangno = 0; / / hangno number of rows to display
for (i = 0; i <32; i + +)
{
PORT1 =* (addr + hangno * 0x600 + i); / / I is 0 to 600 characters of information for the first line of information
/ / 600 ~ 0c00 as the second line of information ...
PORT2 = 0x0ff;
}

Each time you send 32 bytes (16 words), the program compile, no problem, but when the time display 64 characters

(Assuming) shows the chaos, and later changed to

if (hangno == 0x10) hangno = 0; / / hangno number of rows to display
w = hangno * 0x600;
for (i = 0; i <128; i + +)
{
PORT1 =* (addr + w + i); / / I is 0 to 600 characters of information for the first line of information
/ / 600 ~ 0c00 as the second line of information ...
PORT2 = 0x0ff;