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gca1-pi01-en [2018/12/05 00:16]
rainerk
gca1-pi01-en [2020/06/13 19:10] (current)
phg [I2C system]
Line 31: Line 31:
 I2C is basicly made for communication between chips, together on one board.\\ I2C is basicly made for communication between chips, together on one board.\\
 Therefore, according to specifications , the total length of all SDA and SCL wires together should not exceed 1 meter (3' 4''​).\\ Therefore, according to specifications , the total length of all SDA and SCL wires together should not exceed 1 meter (3' 4''​).\\
-This system will be made with addional line drivers, making a total length of 10 meters ​accessable.\\+That 1 meter limit is ver strict, meaning that a few centimeters (or even less inches) longer can be a problem.\\ 
 +Important is to know that this 1 meter means ALL the RocNet cables in this Local RocNet network TOGETHER, conterolled by a Raspberry pi.\\   
 +This system will be made with addional line drivers, making a total length of a few meters ​more possible.\\
 Each board is provided with an extra line driver P82B715 and a low drop voltage regulator to have 3.3 V available.\\ Each board is provided with an extra line driver P82B715 and a low drop voltage regulator to have 3.3 V available.\\
 The regulator skips the need of transporting 3.3 V from the Raspi, which could give more problems than profit.\\ The regulator skips the need of transporting 3.3 V from the Raspi, which could give more problems than profit.\\
 +But it is also important to realise that the supply over the RocNet cable is only 5 Volt.\\
 +And the length of the cabler might be fine for the I2C network uitself, but certainly NOT for the supply in that cable.\\
 +And with a little bit of cable length, that 5 Volt will very fast drop down, making the system unstable.\\
 +Either RJ12 flatcable or RJ45 Ethernet cable is NOT made for current supply.\\
 +So the conclusion here is, use only very short cables, with no more than a total lenght (all cables together!) of 2 -3 meters with one Raspberyy PI.\\
 +The extra avaiable GCA_PI06 will provide enough power, but always measure that voltage on the far ends of this RocNet network.\\
 +As soon as your voltage there (with the system working) drops down to below 4,8 Volt, you are already too far down.\\
 +If you need more I/O you will need multiple Rspberry Pi compters with their own supply.\\
 +Raspberry Pi computers are linked to the Ethernet network, and in that ethernet network there are onloy signals, no current.\\
 +
 +RocNet is not a '​çheap network',​ replacing CAN or Ethernet, if your ideas go that way, please reconsider.\\
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-For more information please see http://​www.nxp.com/​documents/​application_note/​AN10658.pdf ​ \\+For more information ​about cable length with the line driver, ​please see http://​www.nxp.com/​documents/​application_note/​AN10658.pdf ​ \\
  
  
gca1-pi01-en.1543965419.txt.gz · Last modified: 2018/12/05 00:16 by rainerk