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Subject: A question on modbus
From: Amber via Tech-talk <tech-talk at aps.anl.gov>
To: "tech-talk" <tech-talk at aps.anl.gov>
Date: Tue, 11 Jul 2023 16:03:55 +0800
Hello everyone,

I am using a device with Modbus-RTU protocol. The communication data is transmitted in hexadecimal words.
I want to use the modbus module in epics to solve this problelm. 

When reading device data, the follwing sentence is used in the .cmd file:

drvModbusAsynConfigure("V1","Power", 1,3,0,1,0,1000, "Power")

and in the substitution file:

file "../../db/ai.template" { pattern
{P,         R,      PORT,               OFFSET, BITS,  EGUL,  EGUF,   PREC,   SCAN}
{power:,    V_read,   V1,   0,      16,    0.,   655.35,     2,      "I/O Intr"}
}

There is another command to open the device, which should write " \x01 \x05 \x00 \x00 \xFF \x00  \x8C \x3A" to the device.

Command

01

05

00

00

FF

00

8C

3A

Address

Function code

Register address 0

Data 0

CRC

Reply

Be same with command


After reading all the examples I still don't know how to send this command with modbus module correctly. I think I didn't understand them clearly.
Would you like to give me some advice?  Is it suitable to use modbus module?  How to realize it?
Thank you very much.

with my best wishes,
Kevin



Replies:
RE: A question on modbus Mark Rivers via Tech-talk

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