User manual

ManualsBrandsEA ELEKTRO-AUTOMATIK ManualsPower Supplies & Mains AdaptersEA-IF-R1 RS-232 Interface

About the interface cards

The implementation of the VCP driver is easier, but this

driver is more susceptible to communication problems and

errors. It also creates a new COM port for every USB card,

which complicates the port management. The USB driver

requires the user to create own routines, which handle the

USB low level communication, in order to ensure the proper

transport of the communication data of our system. These

routines are not offered by us. Sample code is available on

the web site of the manufacturer FTDI, at www.ftdichip.com.

The USB chip is named FT232B

7.5 Structure of the communication

The communication with the controlled units is based on

these telegram types:

a) Simple message: an object is sent, which shall for instance

set the output voltage. As long as this action is permitted by

the current state of the device, the object is accepted and

executed. The device won’t send any answer. If it’s not per-

mitted it will send an answer, an error message.

b) Query: a query is sent by using a certain object, for in-

stance „get actual values“, and an answer is expected. If

the query is permitted for the current state of the device it

is executed and answered. The answer contains the reque-

sted data. If not permitted it will send an error message as

answer.

c) Event: is an error message, which is sent by the device

without request, for example if the access to an object is not

permitted or if the previous message was not recognized by

any reason, like if it was crippled by external interferences.

Contains an error code.

7.6 Telegram structure IF-R1 and IF-U1

The interface cards IF-R1 and IF-U1 are using the same

telegram structure, the one of the CAN card IF-C1 is diffe-

rent. Read below if you‘re using a IF-C1 card. At the serial

transmission of one byte with the RS232 card following bits

are sent:

Start bit + 8 Data bits + Parity bit + Stop bit

The parity is checked for „odd“.

The USB card is internally working with the RS232 charac-

teristic For both card types it is required to set at least these

transmission parameters for the particular driver:

Baud rate: 57600kBd

Parity: odd

Stop bits: 1

The telegram is structured like this

SD + DN + OBJ + DATA + CS

and is built by these bytes:

Byte 0: SD (start delimiter)

The start delimiter determines how to handle the telegram

furthermore. Meaning of the bits:

Bits 0-3: Data length (Bytes 3-18)

Denethedatalength-1ofthedatainthetelegram.

At a query the data length of the expected data is given

here.

Bit 4

0= Telegram from device to control unit

1= Telegram from control unit to device

Bit 5

0= Singlecast, telegram to a certain device node

1= Broadcast/Multicast, telegram to all device nodes

Broadcast only works for units that are bus connected, like at

CAN.

Bits 6+7: Transmission type

00 = Reserved

01 = Query data

10 = Answer to a query

11 = Send data (without previous request)*

* can also occur from the device

Byte 1: DN (device node)

The device node identifies and adresses devices inside a bus

system. Each node number must only be assigned once. This

is used to address a particular device. Value range: 1...30,

others are invalid. Using CAN, the CAN ID is calculated from

the device node. See section 7.7 for details.

Byte 2: OBJ

The communication objects for a device are addressed by

this byte. In the communication object list (see section 9.3)

the objects and their function(s) are explained in detail.

Byte 3 - 18: Data field

The data field can be 1-16 bytes long, hence the length of

the telegram varies. If a query is sent (PC -> device) and no

data is sent, the data range is not used and the checksum of

the telegram (see below) follows directly after byte 2. Only if

an answer (device -> PC)is sent, even if it is an event, there

will be data of a specific length.

Word x: CS (check sum)

The check sum is always located at the end of the telegram.

It is built by the simple addition of all bytes of the telegram.

It is two bytes long. The high byte is placed before the low

byte (Big Endian Order).

Example of a telegram:

Object no. 71 (query actual values) shall be sent to a de-

vice with device node 1. The telegram has to look like this

(hexadecimal values):

55 01 47 00 9D

The expected answer could look like this:

85 01 47 64 00 1E 00 50 00 01 9F

(this results in 80V, 30A and 2400W at a 80V, 100A and

3000W power supply, like for example the PSI9080-100)

Also see next section for the conversion of set values and

actual values.

More examples in section 9.