MAKEMODBUS - Revision history

Admin at 19:04, 17 January 2017

2017-01-17T19:04:34Z

Admin at 13:17, 4 February 2014

2014-02-04T13:17:32Z

Admin: Created page with "= Action = Creates a MODBUS master/client frame.
2013-02-11T20:35:54Z

Created page with "= Action = Creates a MODBUS master/client frame. </spa..."

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= Action =

Creates a MODBUS master/client frame.

 

 

= Syntax =

PRINT [#x,] MAKEMODBUS(slave, function, address, varbts )

 

 

= Remarks =
<div style="padding: 0px; margin: 0px 0px 0px 4px;">
{| width="597" cellspacing="0" cellpadding="1" border="1" style="border: 2px solid rgb(0, 0, 0); border-spacing: 0px; border-collapse: collapse;"
|- style="vertical-align: top;"
| valign="top" width="11%" style="width: 62px; border: 1px solid rgb(0, 0, 0);" |
slave

| valign="top" width="100%" style="width: 526px; border: 1px solid rgb(0, 0, 0);" |
The slave to address. This is a variable or constant with a valid MODBUS slave to address.

|- style="vertical-align: top;"
| valign="top" width="11%" style="width: 62px; border: 1px solid rgb(0, 0, 0);" |
function

| valign="top" width="100%" style="width: 526px; border: 1px solid rgb(0, 0, 0);" |
The function number. This must be a constant. At the moment the following functions are supported :
<div style="padding: 0px; margin: 0px;">
{| border="0" cellpadding="0" cellspacing="0"
|- valign="baseline" style="vertical-align: baseline;"
| width="13" | •
| 03 : read register(s)
|}
</div><div style="padding: 0px; margin: 0px;">
{| border="0" cellpadding="0" cellspacing="0"
|- valign="baseline" style="vertical-align: baseline;"
| width="13" | •
| 06 : write single register
|}
</div><div style="padding: 0px; margin: 0px;">
{| border="0" cellpadding="0" cellspacing="0"
|- valign="baseline" style="vertical-align: baseline;"
| width="13" | •
| 16 : write multiple registers
|}
</div>
|- style="vertical-align: top;"
| valign="top" width="11%" style="width: 62px; border: 1px solid rgb(0, 0, 0);" |
address

| valign="top" width="100%" style="width: 526px; border: 1px solid rgb(0, 0, 0);" |
The starting address of the register

|- style="vertical-align: top;"
| valign="top" width="11%" style="width: 62px; border: 1px solid rgb(0, 0, 0);" |
varbts

| valign="top" width="100%" style="width: 526px; border: 1px solid rgb(0, 0, 0);" |
For a function that sends data like function 6 and 16, this must be a variable.

For function 06 which can only write a single register, this can be a byte or integer or word.

For function 16 it may be a long, single or double.

For function 6 and 16 the address of the variable is passed to the function.

For function 3 you may also specify the number of bytes to receive.

Or you can use a variable. When you specify a byte, a word will be used anyway since a word (2 bytes) is the minimum in MODBUS protocol.

But when sending data, you can send content of a byte. For the MSB the value 0 will be sent in that case.

|}
</div>
 

The MAKEMODBUS function need to be used in combination with the PRINT statement. It can only be used with the hardware UART(1-4).

The MODBUS protocol is an industry standard. The protocol can be used with RS-232, RS-485 or TCP/IP or CAN.

The current BASCOM implementation only works with RS-232 or RS485.

In MODBUS we use client/master and server/slave. You may see it as a web server and a web browser. The web server is the client/slave that reacts on the master/web browser.

A slave will only respond when it is addressed. All other slaves just keep listening till they are addressed.

An addressed slave will process the data and send a response.

In MODBUS the data is sent with MSB first and LSB last. The special CRC16 checksum is sent LSB first and MSB last.

When multiple registers are sent with function 16, the data is split up into words, and for each word, the MSB-LSB order is used.

For example a LONG is 4 bytes. LSB, NSB1, NSB2, MSB. It would be sent as : NSB1, LSB, MSB, NSB2.

In order to use the MODBUS functionality, you need to include the MODBUS.LBX with the $LIB directive.

Notice that BASCOM only supports the MODBUS master. A MODBUS server that supports the above functions will be available from MCS.

 

 

 

= See also =

[[PRINT]]

 

 

= Example =

 <source lang="bascomavr">
'-----------------------------------------------------------------------------------------
'name : rs485-modbus-master.bas
'copyright : (c) 1995-2008, MCS Electronics
'purpose : demo file for MAKEMODBUS
'micro : Mega162
'suited for demo : yes
'commercial addon needed : no
'-----------------------------------------------------------------------------------------

$regfile = "m162def.dat" ' specify the used micro
$crystal = 8000000
$baud = 19200 ' use baud rate
$hwstack = 42 ' default use 42 for the hardware stack
$swstack = 40 ' default use 40 for the SW stack
$framesize = 40 ' default use 40 for the frame space

$lib "modbus.lbx" ' specify the additional library
Config Print1 = Portb.1 , Mode = Set ' specify RS-485 and direction pin

Rs485dir Alias Portb.1 'make an alias
Config Rs485dir = Output 'set direction register to output
Rs485dir = 0 ' set the pin to 0 for listening

Portc.0 = 1 ' a pin is used with a switch

'The circuit from the help is used. See Using MAX485
' TX RX
' COM0 PD.1 PD.0 rs232 used for debugging
' COM1 PB.3 PB.2 rs485 used for MODBUS halve duplex
' PB.1 data direction rs485

'configure the first UART for RS232
Config Com1 = Dummy , Synchrone = 0 , Parity = None , Stopbits = 1 , Databits = 8 , Clockpol = 0

'configure the second UAR for RS485/MODBUS. Make sure all slaves/servers use the same settings
Config Com2 = 9600 , Synchrone = 0 , Parity = Even , Stopbits = 1 , Databits = 8 , Clockpol = 0

'use OPEN/CLOSE for using the second UART
Open "COM2:" For Binary As #1

'dimension some variables
Dim B As Byte
Dim W As Word
Dim L As Long

W = &H4567 'assign a value
L = &H12345678 'assign a value

Print "RS-485 MODBUS master"
Do
If Pinc.0 = 0 Then ' test switch
Waitms 500 ' delay
Print "send request to slave/server"
' Send one of the following three messages
' Print #1 , Makemodbus(2 , 3 , 8 , 2); ' slave 2, function 3, start address 8, 2 bytes
' Print #1 , Makemodbus(2 , 6 , 8 , W); ' slave 2, function 6, address 8 , value of w
Print #1 , Makemodbus(2 , 16 , 8 , L); ' slave 2, function 16, address 8 , send a long
End If
If Ischarwaiting(#1) <> 0 Then 'was something returned?
B = Waitkey(#1) 'then get it
Print Hex(b) ; ","; 'print the info
End If
Loop

End
</source> {{Languages}}

[[Category:BASCOM Language Reference]]

@@ Zeile 17: / Zeile 17: @@
 = <span class="f_Header">Remarks</span> =
 <div style="padding: 0px; margin: 0px 0px 0px 4px;">
-{| width="597" cellspacing="0" cellpadding="1" border="1" style="border: 2px solid rgb(0, 0, 0); border-spacing: 0px; border-collapse: collapse;"
+{| style="border: solid 2px #000000; border-spacing:0px; border-collapse: collapse;" width="597" cellspacing="0" cellpadding="1" border="1"
 |- style="vertical-align: top;"
-| valign="top" width="11%" style="width: 62px; border: 1px solid rgb(0, 0, 0);" |
+| style="width:11%; border: solid 1px #000000;" width="11%" valign="top" |
 slave
-| valign="top" width="100%" style="width: 526px; border: 1px solid rgb(0, 0, 0);" |
+| style="width:100%; border: solid 1px #000000;" width="100%" valign="top" |
 The slave to address. This is a variable or constant with a valid MODBUS slave to address.
 |- style="vertical-align: top;"
-| valign="top" width="11%" style="width: 62px; border: 1px solid rgb(0, 0, 0);" |
+| style="width:11%; border: solid 1px #000000;" width="11%" valign="top" |
 function
-| valign="top" width="100%" style="width: 526px; border: 1px solid rgb(0, 0, 0);" |
+| style="width:100%; border: solid 1px #000000;" width="100%" valign="top" |
-The function number. This must be a constant. At the moment the following functions are supported&nbsp;:
+The function number. This must be a constant. At the moment the following functions are supported :
 <div style="padding: 0px; margin: 0px;">
-{| border="0" cellpadding="0" cellspacing="0"
+{| cellspacing="0" cellpadding="0" border="0"
-|- valign="baseline" style="vertical-align: baseline;"
+|- style="vertical-align:baseline" valign="baseline"
 | width="13" | <span style="font-size: 10pt; font-family: 'Arial Unicode MS', 'Lucida Sans Unicode', Arial;">•</span>
-| 03&nbsp;: read register(s)
+| 01 : read coils
 |}
 </div><div style="padding: 0px; margin: 0px;">
-{| border="0" cellpadding="0" cellspacing="0"
+{| cellspacing="0" cellpadding="0" border="0"
-|- valign="baseline" style="vertical-align: baseline;"
+|- style="vertical-align:baseline" valign="baseline"
 | width="13" | <span style="font-size: 10pt; font-family: 'Arial Unicode MS', 'Lucida Sans Unicode', Arial;">•</span>
-| 06&nbsp;: write single register
+| 02 : read discrete inputs
 |}
 </div><div style="padding: 0px; margin: 0px;">
-{| border="0" cellpadding="0" cellspacing="0"
+{| cellspacing="0" cellpadding="0" border="0"
-|- valign="baseline" style="vertical-align: baseline;"
+|- style="vertical-align:baseline" valign="baseline"
 | width="13" | <span style="font-size: 10pt; font-family: 'Arial Unicode MS', 'Lucida Sans Unicode', Arial;">•</span>
-| 16&nbsp;: write multiple registers
+| 03 : read register(s)
 |}
 </div>
 |- style="vertical-align: top;"
-| valign="top" width="11%" style="width: 62px; border: 1px solid rgb(0, 0, 0);" |
+| style="width:11%; border: solid 1px #000000;" width="11%" valign="top" |
 address
-| valign="top" width="100%" style="width: 526px; border: 1px solid rgb(0, 0, 0);" |
+| style="width:100%; border: solid 1px #000000;" width="100%" valign="top" |
 The starting address of the register
 |- style="vertical-align: top;"
-| valign="top" width="11%" style="width: 62px; border: 1px solid rgb(0, 0, 0);" |
+| style="width:11%; border: solid 1px #000000;" width="11%" valign="top" |
 varbts
-| valign="top" width="100%" style="width: 526px; border: 1px solid rgb(0, 0, 0);" |
+| style="width:100%; border: solid 1px #000000;" width="100%" valign="top" |
 For a function that sends data like function 6 and 16, this must be a variable.
@@ Zeile 70: / Zeile 92: @@
 For function 6 and 16 the address of the variable is passed to the function.
-For function 3 you may also specify the number of bytes to receive.
+&nbsp;
 Or you can use a variable. When you specify a byte, a word will be used anyway since a word (2 bytes) is the minimum in MODBUS protocol.
@@ Zeile 76: / Zeile 100: @@
 But when sending data, you can send content of a byte. For the MSB the value 0 will be sent in that case.
-|}
+&nbsp;
-</div>
-<span style="font-family: Arial;">&nbsp;</span>
 The MAKEMODBUS function need to be used in combination with the PRINT statement. It can only be used with the hardware UART(1-4).

@@ Zeile 100: / Zeile 100: @@
 In order to use the MODBUS functionality, you need to include the MODBUS.LBX with the $LIB directive.
-Notice that BASCOM only supports the MODBUS master. A MODBUS server that supports the above functions will be available from MCS.
 &nbsp;