usb-Serial-port:how to send a message like Pyserial?

General
1

I am using a usb-serial with /dev/ttyUSB0, in RaspberryPi, I can send/receive messages as following python code,
#python-start
command = b'\x01\x04\x00\x00\x00\x02\x71\xcb'
with serial.Serial("/dev/ttyUSB0", baudrate=9600, timeout=1.0) as ser:
ser.write(command)
s = ser.read(11)
print(s)
##response example,
b'\x01\x04\x04\x08\xb9\x13\x85\xe4\x92'
###python-end

Now, I want to use Node-red "node-red-node-serialport", failed.
What I am trying,
#nodered function
var b = Buffer.from([1,4,0,0,0,2,113,203]);
msg.payload = b;

I tried "inject" with "buffer" ["0x01","0x04","0x00","0x00","0x00","0x02","0xe4","0x92"].
It doesn't work, why?

2

Have you tried injecting a buffer of [1,4,0,0,0,2,113,203]

Perhaps you also need to send an end character like LF or CR or ETX?

The end char can be set in the serial node settings.

3

and which serial node are you using - from the look of your python you should be using the serial request node.

4

Thank you for your help~,
Hardware: {Raspberry Pi 4 / [usb(ch340)-rs485]}====={sensor:temperature}
Software: {os:"Raspbian GNU/Linux 10 (buster)", [python:3.7.3, pyserial :3.4], Node-RED version: v1.0.3, Node.js version: v10.15.2, Linux 4.19.97-v7l+ arm LE, node-red-node-serialport: 0.10.1}

because I want to request/reply and retrieve the values, so Request-node.

5

unfortunately, LF,CR,LF/CR,ETX verified, as "https://www.cisco.com/c/en/us/td/docs/ios/12_4/cfg_fund/command/reference/cfnapph.html"

Forgive me on the long post.
And here is my flow,
[{"id":"8cacebbb.7d8c18","type":"inject","z":"2924cfef.17058","name":"","topic":"","payload":"[1,4,0,0,0,2,113,203]","payloadType":"bin","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":390,"y":320,"wires":[["6efba883.73d928","29211535.f8deca"]]},{"id":"29211535.f8deca","type":"debug","z":"2924cfef.17058","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","targetType":"full","x":550,"y":240,"wires":},{"id":"6efba883.73d928","type":"serial request","z":"2924cfef.17058","name":"","serial":"fa73b26e.94d4c","x":550,"y":320,"wires":[["29211535.f8deca"]]},{"id":"fa73b26e.94d4c","type":"serial-port","z":"","serialport":"/dev/ttyS0","serialbaud":"9600","databits":"8","parity":"none","stopbits":"1","waitfor":"","dtr":"none","rts":"none","cts":"none","dsr":"none","newline":"1000","bin":"bin","out":"time","addchar":"","responsetimeout":"10000"}]

6

Thank you Steve-Mcl, it works as what you said.
Here is change,
var buf = Buffer.from([0x01,0x04,0x00,0x00,0x00,0x02,0x71,0xcb,0xda]);

Thank you all, for your help!

7

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