Hi I'm using the node-red-node-serialport to send / receive using a CC2530 and CC2531 TI serial device. The device sends bytes with the following frame format: Byte 1 - SOF (0xFE) Byte 2 - Length of message Byte 3 - Command 0 (What type of message it is) Byte 4 - Command 1 (message type) Byte…

Are you able to modify your device to use something standard like ETX as an end marker? or a LF or CR? Essentially use a character you know will NOT appear in the data as the end marker?

Is there really only 0.5ms (ie 1/2000 seconds) gap between the received messages? If the device sent out messages with a larger gap then you should be able to use that reliably.

I have been researching if I can use some sort of other character to split the messages. If I use ETX (hex 0x03), the data could contain 0x03. CR \r is hex 0x0d and new line \n - 0x0a. Which are all valid hex values which can be in the message. I can change the last character if I have to but wo…

I may need to split the messages using the split by silence method in the serial node. Then use a function node using the startmarker and length byte to further split the combined buffers. I will do some testing. Thanks for the suggestion. I'm still not sure what this statement meant : Tip: "In…

Hi - it means that (for the serial request node) - if you configure it to expect say 50 chars - then as part of your request you can say - actually no I only want 20 ... but it is part of the request so doing what you want is not really possible as yo would need to set the start char - ask for 2 - t…

Is it possible to split on more than one character with the serial node like you can with the TCP node? then perhaps the OP could use a combination of characters that would not normally be sent e.g. ETX * EOT

It would be great if the serial node can split on more than one character. I modified the serial node java script codes to add splitting on more than one character, since my case is more complicated (the messages coming in have variable length).

happy to look at that as a pull request if you like.

If the OP had control of the sending device then he could ensure there is always an appropriate silence period between messages.

Node-red-node-serialport Buffer Length

Core Development Feature Requests

Colin 23 December 2020 11:52 5

Do you always know that eventually there will be a larger gap? If so then set the silence time so as to split on the larger gap, when any sequence of messages is complete, and accept the fact that sometimes you will get more than one message in a buffer. Then split the buffer in node red using the start char and buffer length, with the end char as a confirmation that you have a complete buffer.

1 Like

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Node-red-node-serialport Buffer Length

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