Have done 485 bus by multiple sensor's brother? Encounter a situation now, is on the bus at the same time by multiple sensors at the same time, there will be a sensor does not return data frames, if there is no return to the data frame sensor, only he got on the bus, but normal return data, have a brother know this is what happened?

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The root bus took a wind speed, a wind direction, a screen, a rain, and wind speed and direction is normal, but the screen when the data is no sometimes, most of the time is 0, but when there are data is the correct data, no rainfall data, 0 directly

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Send the frame is no problem

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Modbus rtu polling 1 s, the former half a second to send, after half a second

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Meet the terminal resistance

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1, use what the agreement? If is the modbus from machine have the same address?
2, the terminal matching resistance meet the euro 120?
3, the direct use serial assistants as host to try polling

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refer to 6th floor xws245925587 response:

1, use what the agreement? If is the modbus from machine have the same address?
2, the terminal matching resistance meet the euro 120?
3, the direct use serial assistants as host to try polling

line short no more than 30 m, so he didn't answer the end resistance, the third point you mentioned, I went to the scene to try

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reference 5 floor yishumei reply:

terminal resistance after it

up to 20 m or so so I didn't answer the end resistance, strange

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Machine more than 485 bus communication protocol must have the corresponding hardware and software, each site must be set address, use such as modbus protocol, the terminal resistance must match

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Host bus connection from the machine structure is the star, main line, Daisy chain? Suggest using bus terminal 120 ohm resistor matching

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Can bus sensors have the same address, the address conflict, hang on the bus, each sensor alone reading its address, change the address is the same, to ensure that each sensor's address is different, and not to 0, then all connected, can try to read the data, if the address without conflict, then the connection is correct and reliable, do not rule out the sensor itself has a problem,

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1, RS485 bus terminal resistance is important
2, from the machine address cannot be the same
3, master station to send and receive the timing to correct and from the station to send and receive,
That is:
(1), when the Lord sent, all from the station must be in listening state
(2), the main is sent, must wait until the data is sent to completely from the stand, can/delivery mode switch to [listen mode]
Many students sent by air to break is problematic drops! The RS485 bus and the last byte must complete the interrupt signal, with sending switch at the end of the last byte sent to] [listening mode,
(3) from the machine after receiving the message and waiting for the detected 3.5 time not to receive the rest of the characters of the characters, that has received a complete frame of message, began to parse the message parsing is complete, send a message to the main front, to the mode switch, the switch from [listen mode] to [delivery mode],
Receive began to send message to the main,
Many students sent by air to break is problematic drops! The RS485 bus and the last byte must complete the interrupt signal, with sending switch at the end of the last byte sent to] [listening mode,

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All from a station on the initial electricity, in [listen mode];
Master station just on electricity, is in [delivery mode]

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Although the distance is not far away and you wiring and cabling to environmental factors,

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Want to ask, the host multiple sensors connected to the bus send inquiry frame, is how to the receiving sensor? Is a a matching address? According to the address location directly to the sensor