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Main Board

by Sébastien Lelong — last modified 2008-06-04 20:40

Author:	Sébastien Lelong, The SirBot Project, 2005

Revision History
Revision: 409	Initial creation
Revision: 441	Convert to REST
$Revision: 538 $	include 16F88: changed doc and diagrams

Abtract

The Main Board is the central electronic board of the SirBot Project. It contains a microcontroller which permits to control every SirBot Modules (external boards).

The version of this board has a integrated RS232 module for communication capabilities via the serial port.

Currently, two microcontrollers can be used, with minor modifications in the assembly: PIC 1F628 and PIC 16F88. This only difference is about connecting the UART module. PIC 16F88 is a better choice, as it has more memory, ADC (analog-to-digital) and mostly it can be programmed using a bootloader (such as TinyBootloader, fully tested, see python version pytbl.py in the 3rd party SirBot distrib).

Table of Contents

Electronic diagram
Electronic assembly
Results
Tests

Electronic diagram

The Main Board corresponds to the following diagram (here for a 16F628):

For the RS232 module, we have the following diagram:

Microcontrollers pin diagrams

The following pictures show pin diagrams for 16F628 and 16F88 microcontrollers, with differences about UART pins.

Main Board components

Components list
Name	Value	Picture
R1, R2	Resistances 1
C1	Condenser 10µF
C2	Condenser 100nF
C3, C4	Condenser 22pF
C5, ..., C9	Condenser 1µF
D	Diode 1N4001 or 1N4004
L1	Led
Q	Quartz 20MHz (or 4/10 Mhz, preferably 20MHz)
REG	Voltage regulator 7805
CI1	Microchip PIC 16F628 or PIC 16F88
CI MAX232	MAX232
J	Power supply connector 2.5mm
K	26 pins connector
K2	RS232 connector (male)

Note:	This board needs a (at least) 9V/500mA power supply, not regulated (there is a voltage regulator on the board).

Connection specifications

The Main Board provides a bus connection (via connector K). Every external modules have this connector so they can be plugged-in and controlled by the Main Board. hus, this bus provides communication capabilities between every boards and must respect the following specifications:

The connector has 26 pins.
18 pins are used to have access to every pin of the PIC 16F628
2 pins are used to provide power supply to other modules.
So, 6 pins aren't used yet

The connection diagram is the following:

Electronic assembly

The following pictures show the implementation of the components on a board (with holes) and the reverse side of the board. Layout differences are shown in red whether 16F88 or 16F628 is used.