Atmega8 PLC

Atmega8 microcontroller connected with the PLC functionality of the computer control boards successfully influenced the course but would not have developed an application's features üstekik shared resources

I2C bus interface tutorial

History of the I2C bus

In the late seventies of the previous century, small microprocessors and digital operating integrated circuits were slowly overtaking jobs in consumer products like television sets from analog circuits. Philips—one of the main manufacturers of consumer electronics—was looking for an interface that could be used to let ICs communicate with each other with a low-cost connection and at moderate speeds. The common method of inter-IC communication at that time was via a parallel 8 bit wide bus. This bus structure—which is also used to connect memory and peripherals to CPUs—requires not only eight data lines for the data transfer, but also several lines for addressing specific peripheral ICs. Philips researched for a way to reduce the necessary area on the printed circuit boards for these buses and the costs involved by reducing the number of communication lines to only two. This inter-IC bus was called IIC or I2C and became widely implemented in situations where cost and size reduction were more important than data speed.

RS232 serial null modem cable wiring and tutorial

Null modem, an introduction

Serial communications with RS232. One of the oldest and most widely spread communication methods in computer world. The way this type of communication can be performed is pretty well defined in standards. I.e. with one exception. The standards show the use of DTE/DCE communication, the way a computer should communicate with a peripheral device like a modem. For your information, DTE means data terminal equipment (computers etc.) where DCE is the abbreviation of data communication equipment (modems). One of the main uses of serial communication today where no modem is involved—a serial null modem configuration with DTE/DTE communication—is not so well defined, especially when it comes to flow control. The terminology null modem for the situation where two computers communicate directly is so often used nowadays, that most people don't realize anymore the origin of the phrase and that a null modem connection is an exception, not the rule.

RS232 serial spy monitor cable

Introduction on monitoring serial RS232 data

The RS232 standard defines an asynchronous way of communication between DTE, data terminal equipment (computers, printers, etc.) and DCE, data communication equipment (modems). This type of communication has become the minority and nowadays serial communications is mainly between two DTE devices using a null modem cable. Although this is 1:1 communication, it is possible with special cables to monitor the data streams.

RS232 provides 2 data lines for each data channel. One is for transmitting data and the other for receiving. Because of these two separate lines, data can be send full duplex. This means that both ends can send and receive data simultaneously without mutual interference. In most situations however the high level communication protocol only allows half duplex communications because most simple protocols with external devices work with a master-slave, or question-answer configuration. One of the parties is the master which is in charge of communications. This master sends commands and requests to the slave which responds to them. The slave will never by itself start a communication sequence so in practise the communication is half duplex: There is no single moment when both sides send data simultaneously.

S7/300 (PC Adapter)

HMI Setting:

Parameters	Recommend	Options	Notes
PLC Type	Siemens S7/300 PC Adapter	Siemens S7/300 PC Adapter
Com Port	RS232	RS232/RS485	must set as 8 to this protocol
Baud Rate	19200/38400	9600/19200/38400/57600/115200	must same as the PLC setting
Parity bit	Odd	Even/ Odd/ None	must same as the PLC setting
Data Bits	8	07/08/09	must same as the PLC setting
Stop Bits	1	1,2	must same as the PLC setting
HMI Station No.	0	0-255	Does not apply to this protocol
PLC Station No.	2	0-255	must same as the PLC setting

S7/200 Hardware Setting

Siemens S7/200 series PLC

(CPU212/214/215/216/221/222/224/226/226XM)

HMI Setting:

Parameters	Recommend	Options	Notes
PLC Type	S7/200
Com Port	RS485	RS485
Baud Rate	9600	9600/19200	must same as the PLC setting
Parity bit	Even	Even, Odd, None	must same as the PLC setting
Data Bits	8	7,8	must same as the PLC setting
Stop Bits	1	1,2	must same as the PLC setting
HMI Station No.	0	0-255
PLC Station No.	2	0-126	must same as the PLC setting

On Line Simulator
YES

Direct On Line Simulator
YES

Extend Address Mode
NO

Modbus RTU Controller

Modbus RTU Controller

HMI Setting :

Going online with an USB/RS232 adapter

Todays laptops come with no onboard serial ports so you have two solutions: rather costly PCMCIA serial cards (watch for base address and IRQ settable ones only) or cheap USB/RS232 adapters.

Emulating a serial port with a USB/RS232 converter is not always successful and might depend on the specific type of USB converter you are using and related Windows drivers. Just to mess up things, the emulated serial port may be listed as COM1 in the Windows' control panel but accessible only as COM3 by the Step-5 programming software. Once you succeed in having the S5 software communicating with the PLC, for the most of joy you may then experience sudden system crashes (blue screens) with no apparent reason.

Omron PLC cable layouts

The PLC's from Omron can be connected to various peripheral equipment. Each device requires its own cable layout. Only the more common cables are shown here.