I/O device on a microcontroller. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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I/O device on a microcontroller. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Microcontrollers

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This input/output device can be used for any purpose where buttons and indication are needed. The device allows you to display numbers from 0 to 9, symbols "P, L, C, H", a minus sign and a blank "blank" on the indicators.

(click to enlarge)

This device is controlled via USART, 19200 baud. Every 500ms (0.5 sec.) the device sends the character "S". The accuracy was set by computer. Every 10ms, the device sends two bytes - the character "K" and, the second byte, the value of the buttons. In the second byte, the value of each bit corresponds to the status of the button (1-closed, 0-open).

To light a symbol on the indicator, you need to send 5 bytes to the device. The first byte is the character code "I", 2,3,4,5 bytes, respectively, the values of the indicators.

The indicator displays numbers from 0 to 9, symbols "P, L, C, H", a minus sign and a blank "blank".
Send values :
The numbers 0-9 are the corresponding number.
Symbols "P,L,C,H" - number 10-13.
Minus sign - number 14.
Void "blank" - number 15.

LEDs are lit by one byte in place with indicator dots. To light them, you need to send the "L" character and the status byte of the LEDs and dots to the device. In the status byte, bits 0,2,4,6 correspond to the values of the LEDs. Bits 1,3,5,7 - the value of the indicator points.

I/O device on a microcontroller. Photo of the assembled device

The indicators are inside with registers and their own decoder, so other characters are not the same. I don't know how to replace them. But I think others with the same internal structure will do.

It must be remembered that the signals at the input of the device must be TTL level. If you plan to use the device with a computer, you need to get the level of TTL signals from the RS232 signal levels. To do this, you need to use RS232 - TTL adapters, for example eldigi.ru/site/comp/8.php, or something simpler, on several transistors. You can also connect to a USB port, for this you will need a USB to RS232 adapter. eldigi.ru/site/comp/3.php.

The device is powered by a stable 5 V supply. You can power it from a separate power source, then you will need to connect the grounds of the device and the computer. You can power the device directly from the computer, because. it also has a stabilized 5 V.

74LS245 is our 555AP6 - Bus shaper.
IR82 - register.

Download firmware

Author: Alexey Klyushnikov, Ivanovo E-Mail: al.kl [dog] mail.ru; Publication: cxem.net

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