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natcl / Artnet

An Art-Net library for Teensy, Arduino and ESP boards
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Shouldn't this iterate from 0 to i < 8? Instead of 9? #40

Closed marcel303 closed 5 years ago

marcel303 commented 5 years ago

https://github.com/natcl/Artnet/blob/8aa00cc0a82b3c709ccfe6d526d932822e211960/Artnet.cpp#L59

natcl commented 5 years ago

Normally it should be ok as there is a null character at the end:

define ART_NET_ID "Art-Net\0"

marcel303 commented 5 years ago

Yes, but iterating from 0 to 9 means 9 bytes are being checked. The ninth byte (at index 8) is the first byte of the opcode. See https://en.wikipedia.org/wiki/Art-Net.

Just starting out with ArtNet and reading up on it, so I may be wrong, but I think the reason it works ok is because the opcode for OpDmx is 0x5000, and the opcode is written low byte first, followed by the high byte. So the 0x00 comes first and then 0x50. It's a zero, but not the zero you think it is. :-) The "Art-Net\0" string has indeed two trailing zeroes so it'll work fine. But should you ever want to handle opcodes with a non-zero low byte it'll break.

natcl commented 5 years ago

ahh good catch, will fix thanks !

marcel303 commented 5 years ago

Sure, no problem. Thank you for making such an easy to use library available! I will experiment some more with your code over the weekend. Mac -> Wifi -> ESP32 -> Dmx serial chip -> Let there be Light. :-)

natcl commented 5 years ago

No problem ! Let me know how it goes :)

marcel303 commented 5 years ago

Ha @natcl Just writing back to you to let you know it works wonderfully. Works great out of the proverbial box with the ESP32 and the lights I've got! Thanks!

natcl commented 5 years ago

Excellent ! :)