Training program: Mechanic - electrotechnician

Program name: Digital processing - microprocessorsIII. classMicrocontrollers

Elaborated by: Vlastimil Vlček

Projekt Anglicky v odborných předmětech, CZ.1.07/1.3.09/04.0002

je spolufinancován Evropským sociálním fondem a státním rozpočtem

České republiky.

Peripheral devices are parts of the equipment connected to the input or output ports of a microcontroller (LED diodes, displays, relays, keyboard).

The devices connected to the input ports are read by a microcontroller, whereas the devices connected to the ports in an output mode are being written in.

It is desirable to ensure that careless handling with the ports of a microcontroller resulting in their damage (due to static electricity, careless plugging in of a microcontroller, etc.) does not occur.

ATTENTION!Maximum permitted output current of one pin is 25mA!

The sum of currents of all output pins of one port is 90mA at the most !!!

Microcontroller and the surrounding worldConnection of peripheral devices

Button as an input device

Metal contact = bouncing, oxidation, dirt, wearMetal gilded contact = bouncing, dirtRubber with a carbon layer = dirt, wearElectronic switch (Hall probe) = faultless

PORT A = inputPORT B = output

1st cycle 2nd cycle 3rd cycle 4th cycle

RB0 H L L L

RB1 L H L L

RB2 L L H L

RB3 L L L H

For 16 buttons, 8 lines are sufficient:

Keyboard as an input device(matrix circuit)

LED diode as an output device

Triggering of L levels at the RB0 output

Triggering of H levels at the RB0 output

ATTENTION!Do not forget the protection diode D1!

Relay as an output device

LED display as an output device(common anode circuit)

A quad of LED displays as an output device(multiplex control)

A quad of LED displays as an output device(serial data input)

Scheme of a preparation used for teaching microcontrollers (PIC16F883)

Summary of the subject matter

• What is a peripheral device?• How do you connect a button to a microcontroller? • How do you connect a relay with the pull-up current of

50mA to a microcontroller?

Summary of the subject matter

• Explain the principle of display multiplex control!• How do you ensure that the ports of a microcontroller are

protected from damage due to careless handling or static electricity?

• What is the function of a protection diode in a relay?

Datasheet Microchip PIC16F882/883/884/886/887 DS41291E (http://www.microchip.com)

Jiří Hrbáček: Mikrořadiče PIC16CXX a vývojový kit PICSTART (BEN – technická literatura, Praha 2001 3. dotisk 4. vydání)

Jiří Hrbáček: Komunikace mikrokontroléru s okolím 1 ((BEN – technická literatura, Praha 2002)

References