69 lines
2.1 KiB
Plaintext
69 lines
2.1 KiB
Plaintext
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FREEMODBUS 1.5 ATSAM3S EXAMPLE
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==============================
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REQUIREMENTS
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============
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This example contains a simple demo program for FreeMODBUS for the AT91SAM3S
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Cortex M3 controllers on the SAM3S-EK [0] evaluation kit. It requires a wired
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RS485 connection to a host processor and a MODBUS master software on the PC
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side to be useful. Demo versions of MODBUS master stacks can be found in
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[1], [2] and [3]. Commercial MODBUS stacks are available from [4].
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INSTALLATION
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============
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The SAM3S-EK evaluation board should be modified as following to enable RS485
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data transmission.
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- Place Jumpers JP11, JP10 and JP12
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- Place a solder drop accross R25
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Warning: The RS485 shares data lines with USART1. It is therefore absolutely
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necessary to set PA23 to a high level.
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SOURCE
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======
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TESTING
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=======
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Start the MODBUS sample application and test if the input registers starting
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at protocol address 1000 can be read. There are four registers values avai-
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lable and the output should look like:
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Polling slave (Ctrl-C to stop) ...
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[1000]: 6474
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[1001]: 0
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[1002]: 0
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[1003]: 0
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Polling slave (Ctrl-C to stop) ...
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[1000]: -8831
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[1001]: 0
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[1002]: 0
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[1003]: 0
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Polling slave (Ctrl-C to stop) ...
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The simple testing utility used in the 'demo_rtu.bat' script can be found at
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[3].
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PROBLEMS
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========
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In case you can get no communication working make sure that the RS485 line is
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biased correctly. The SAM3S-EK does not populate the RS485 bias resistors by
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default and if you have a RS485 master which does not bias the lines either
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you will get wrong characters. For this R24 and R30 on the bottom side of the
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evaluation kit of the PCB should be populated.
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REFERENCES
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==========
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[0] Atmel SAM3S-EK: http://www.atmel.com/dyn/products/tools_card_v2.asp?tool_id=4678
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[1] WinTech ModScan32: http://www.win-tech.com/html/modscan32.htm
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[2] Modus Poll: http://www.modbustools.com/modbus_poll.asp
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[3] FieldTalk Modpoll: http://www.focus-sw.com/fieldtalk/modpoll.html
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[4] Embedded Solutions: http://www.embedded-solutions.at
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Version: $Id: README.txt,v 1.1 2010/06/06 13:07:19 wolti Exp $
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