Olimex PIC-IO User guide

OLIMEX© 2012 PIC-IO User's Manual

PIC-IO development board

User's Manual

Rev.C, October 2012

Copyright(c) 2012, OLIMEX Ltd, All rights reserved

All boards produced by Olimex are ROHS compliant

OLIMEX© 2012 PIC-IO User's Manual

INTRODUCTION:

PIC-IO board was designed as simple platform which to allow control of appliances and
devices with PIC, the idea was to build something like tiny PLC controller which is possible
to program in C or assembler instead of the weird PLC relay language.

Let’s see what we have on board:

Four High voltage/ High Current relays – with NO-NC-COM contacts available on terminal
block. The relay switching current is rated: 15A/125VAC, 10A/250VAC, 15A/24VDC. Note
that these relays are good for switching resistive loads, but if you have to commutate
inductive loads the relays will wear off quickly due to the sparking when disconnect the
inductive loads (like motors).

Each relay have status LED associated with it so you can easy see which relay is in ON and
which in OFF state.

O1 is connected to RA3 CMP1 and PIC CCP module can be used to generate ON/OFF pulses.

O2-O3-O4 are connected to RA2-RA1-RA0.

Four opto-isolated inputs will allow to detect voltages in range +5-24VDC. Opto-couplers are
fast and switch On/Off for 10 uS, so quick signals could be detected.

!NOTE for owners of MOD-IO prior to revision C1: the above information is correct
only for the opto-isolated couplers – the board is capable to handle up to 22VDC for
them. You need to swap R1, R2, R3, R4 - 330R resistors with 470R ones be able to use
24VDC! This has been fixed in the latest revision as seen in the schematics.

I1 is connected to RA4 and is good for counting as this pin is connected to PIC T0CKI.

I2 is connected to RB0 which is INT and generates interrupts.

I3 is connected to CCP1 and is good for pulse width measurement.

I4 is connected to RB4.

The inputs have status LEDs so easy could be seen which input have voltage. Note that the
optocouplers inverse the levels i.e. when on the input have +5V the PIC pin will read “0” and
vice versa.

Status LED is connected to RB5.

PIC-IO have RS232 connector, but the driver is made by tricky level shifter which uses the
other side RS232 negative levels to generate the PIC-IO levels, so on the other side you must

OLIMEX© 2012 PIC-IO User's Manual

have real RS232 driver (like PC) if you try to connect two PIC-IO boards by RS232 the
connection will fail as no one of the boards will generate the negative levels.

The on-board ICSP connector allow you to program the PIC on the board without pulling it of
the socket, by ICSP programmer like PIC-MCP, PIC-MCP-USB, PIC-PG1, PIC-PG2, PIC­PG3, PIC-PG4 or to program and debug it with PIC-ICD2, PIC-ICD2-POCKET or PIC­ICD2-TINY. IMPORTANT: all programmers provide power supply through ICSP connector
during the programming PIC-IO should not be powered via the external power jack!

The power supply circuit have protection diode for reverse connection. The positive point is
the internal pin of the power jack. The input voltage could be in range 12–14V DC.

The oscillator circuit is made with 20 Mhz crystal oscillator, so you can run your PIC at
maximum performance.

The RESET is connected with 10K to +5V and allow safe use of PIC-ICD2 or PIC-MCP
programming.