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gca1-pi01-en
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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] |
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| 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.\\ | ||
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| + | 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
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