Running line on the microcontroller. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Microcontrollers

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The proposed design of the "creeping line" can serve for advertising, information, entertainment and other purposes. When developing the design, one of the tasks was maximum versatility: the ability to use a scoreboard with a different number of segments, as well as getting rid of a standard character generator (character generator). And to enable the user directly, without changing the program and changing the controller, to create (draw) images thanks to a convenient interface - a computer PS / 2 mouse.

Features

Principled controller block diagram (Fig. 1). The quartz resonator ZQ1 is connected to the built-in clock generator of the controller DD1. The MCLR reset input (pin 1) is connected directly to +5V, a stable reset provides an activated built-in reset timer when the controller is powered on. Control buttons SA1-SA2 are connected to port_B of the controller and loaded with built-in "pull-up" resistors. The mouse is connected to the device via a PS/2 (MiniDIN-6) connector and is serviced by the controller's control program. To the pins of port_C PC3 and PC4 connected EEPROM graphics DD2 with serial exchange on the interface I²C by means of the MSSP module built into the controller, and operates at an increased CLOCK (1 MHz) frequency.

Rice. 1. Diagram of the controller block (click to enlarge)

Principled diagram of the indicator block. On fig. 2 shows the control scheme of the LED matrix using decoders. The use of K555ID10 decoders is good because they have powerful open-collector outputs. It is possible to use other decoders, for example, K155ID3, K555ID4, ID7, which, however, have a lower load capacity at the outputs. To reduce the number of in-line decoders, which is especially important with a large matrix length, matrix row multiplexers are used, made on DD1, DD2 bus driver chips. Thus, increasing the number of lines by 2 times justifies itself by reducing the number of ordinary decoders by the same amount.

Rice. 2. Schematic diagram of the indicator unit

The RES signal, which is set to 1 at the beginning of the sweep, resets the DD3 counter and connects the first row of the matrix through the DD5 decoder. Next, the RES signal goes to level 0 and, by means of a signal drop CLK, the counter DD1 is increased by 3 and the next row of the matrix is ​​connected through the decoder DD5. On fig. 3. shows the control scheme of the LED matrix using shift registers.

This circuit is simpler, but the outputs of the shift registers are less powerful, and if you need to get more brightness of the LEDs, each output must be supplemented with a transistor switch. A buffer amplifier is made on the DD1 chip. The KR1533IR24 registers are convenient in that they have a separate carry output from the high order and are widely used. When using K555IR8 registers or especially convenient 24-bit KR1533IR31 registers and combining them (if the matrix LEDs are connected directly to their outputs), then the last transfer bit must be connected to the LEDs only through a transistor switch, because loaded on a number of LEDs, the output will not be able to provide the necessary logic levels.

Rice. 3. LED matrix control circuit using shift registers

At the beginning of the image sweep, the DAT signal goes to level 0 and, using the edge of the CLK signal, 0 is written to the first bit of the shift register. Further, the DAT signal goes to level 1 and, using the clock signal CLK, a sequential shift of 0 into the next bit of the register occurs, thus switching the corresponding row of the matrix. If it is necessary to use an LED matrix with a "common anode" (i.e., a number of LEDs are combined by anodes), then instead of the DAT signal, an inverse RES signal must be applied to the input of the first register, and a sequential shift of level 1 will occur at the outputs of the registers. Buffer amplifier DD1 then needs to be replaced with K555AP3 which inverts the output signals, while pin 19 must be connected to ground.

Construction and details. Controller DD1 PIC16F877 4 MHz in a DIP package, it is also possible to use the PIC16F874 controller, which differs from F877 in a smaller amount of memory that is not used by the program. It is possible to replace the DD2 EEPROM with 24C01/02/04/08/ having 128/256/512/1024 bytes, respectively, the missing memory sizes will be read as units. Microcircuits of the K555 series can be replaced with similar ones from the KR1533 or K155 series. The scoreboard was made on ALS362B LED indicators (4 rectangular LEDs) according to the scheme with decoders and line switching. Structurally, the scoreboard can be made on a board made of foil fiberglass, with drilled holes for the LED leads and cut out the longitudinal tracks of the rows with a cutter, solder the rows with a mounting wire. At the bottom of the board, cut out contact pads for control microcircuits. The display unit is connected by a cable to the controller board.

Management

В editor mode (switch SA4 open) moving the mouse over the coordinates changes the corresponding position of the cursor (luminous LED if the image element behind it is off and not luminous if vice versa). pressing on the left button mouse leads to the removal/appearance, respectively, of the luminous/non-luminous selected image element. pressing to the right the mouse button only deletes the selected item. pressing to the middle the mouse button only turns on the selected image element. Having reached, by moving the cursor along the X coordinate, one of the edges of the indicator, its further movement will cause the image to "scroll" in the corresponding direction. The following functions are also available in the "Editor" mode: Closing the contacts of switch SA4 will put the device directly into running line mode. Service options such as: the beginning of the ticker, the end, the speed, and also, if necessary, the place of the temporary stop are determined by the parameters in "Settings" mode. "Settings" mode accessible from the "Editor" mode by pressing to the SA1 button. Note. The minimum size of the LED matrix is ​​23x5 due to the fact that in this mode, with a smaller number of LEDs, it will be impossible to see the numbers on the display, in principle, the dimensions of the matrix are not limited. As a result, two numbers will appear on the display: the number on the left means the parameter number, the number on the right is its value. The parameter functions are shown in the following table:

Parameter No.	Range of values	Function
0	0-2047	Determines where the scroll starts in the "marquee"
1	0-2047	Specifies the end of the scroll in the "marquee"
2	0-2047	Determines the place of temporary stop of the "marquee"
3	0-255	Determines the duration of the temporary stop of the "creeping line". A value of 1 excludes a stop.
4	0-2047	Determines the sweep frequency of the "Crawling Line" and, accordingly, its speed.
5	0-255	Specifies the physical length of the device's LED matrix
6	0-2047	Determines the sweep frequency in all modes except "Crawling Line"
7	0-255	Specifies the duration of the delay during writing to the EEPROM

In this mode, the mouse performs the following functions: moving along the X coordinate will change the number of the edited parameter. By pressing and holding left button mouse and moving it along the X coordinate will change the value of the selected parameter. Clicking on right button mouse will exit to editor mode. To define numerical values ​​for functions such as start/end/break point, the menu that appears when you press and hold the SA3 button in the "Editor" mode. A number will appear on the display indicating the position of the cursor along the X coordinate in the memory field (0-2047). Also being in this mode (i.e. holding the SA3 button) short press on SA4 button will clear that page of memory (256 bytes) in which the cursor was currently located. After checking the changes made to the parameters, if necessary, you can save them as start ones when the device is turned on for a short time. by pressing SA3, the values ​​will be written to the non-volatile data memory of the controller.

When first turned on

1. Enter the "Settings" mode by pressing the SA1 button, selecting parameter No. 5, set the value equal to the length of the matrix
2. In parameter No. 6, set the value corresponding to the optimal flicker frequency
3. Clear the required amount of EEPROM memory (see above)
4. By selecting the value of parameter No. 7 (aiming for the smallest value), eliminate the "blurring" of the image to the right of the cursor on the display after pressing one of the mouse buttons in the "Editor" mode. This parameter depends on the speed of the EEPROM
5. Write the changes to the non-volatile data memory of the controller.

Notes

1. If the SA4 switch is closed when the power is turned on, the mouse will not be initialized (it may be absent) and will not work when you exit the "Editor" mode.

2. If there is no mouse and the power is turned on, the device will not work until the mouse is connected.

3. Disconnecting the mouse when the device is turned on and then connecting it will lead to its software non-functioning (it is necessary to re-initialize it when the power is turned on).

Publication: cxem.net

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