I2C Error Compendium: Difference between revisions
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I2C errors are probably the most annoying | I2C errors are probably the most annoying side effect of the technology we are using in our brushless gimbals. Many discussions, and advices on how to avoid them, are found on the web, and also some myths. | ||
I2C errors occur then the signals on the I2C clock and data lines are disturbed beyond certain limits, and this happens due to two main reason: | I2C errors occur then the signals on the I2C clock and data lines are disturbed beyond certain limits, and this happens due to two main reason: | ||
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* induced signal disturbances due to capacitive coupling to outside fields | * induced signal disturbances due to capacitive coupling to outside fields | ||
Importantly, all error sources add up. One hence can't give | Importantly, all error sources add up. One hence can't give decisive threshold values, such as that e.g. the length of the I2C wires should be shorter than 40 cm. Without any further error sources one might be able to use even much longer wires, while if motor wires are nearby only shorter wires might be acceptable. It's like a glass of wine: When it's full, it's full. It doesn't matter if it had been filled with Bordeaux, Chianti, or any mixture. When the glass is filled only a tiny bit with Bordeaux, one can add a lot of Chianti before it overflows, but when the glass is nearly filled with Bordeaux, only a tiny drop of Chianti is acceptable. | ||
== Capacitive Load == | == Capacitive Load == | ||
== Induced Signal Disturbances == | Capacitive load decreases the slew rate of the signal, and eventually prevents the electronics to detect it correctly, and an I2C error occurs. | ||
Capacitive load | |||
== Induced Signal Disturbances ==, | |||
== Practical Implications == | == Practical Implications == | ||
Revision as of 23:03, 10 January 2015
I2C errors are probably the most annoying side effect of the technology we are using in our brushless gimbals. Many discussions, and advices on how to avoid them, are found on the web, and also some myths.
I2C errors occur then the signals on the I2C clock and data lines are disturbed beyond certain limits, and this happens due to two main reason:
- capacitive load on the I2C clock and/or data lines
- induced signal disturbances due to capacitive coupling to outside fields
Importantly, all error sources add up. One hence can't give decisive threshold values, such as that e.g. the length of the I2C wires should be shorter than 40 cm. Without any further error sources one might be able to use even much longer wires, while if motor wires are nearby only shorter wires might be acceptable. It's like a glass of wine: When it's full, it's full. It doesn't matter if it had been filled with Bordeaux, Chianti, or any mixture. When the glass is filled only a tiny bit with Bordeaux, one can add a lot of Chianti before it overflows, but when the glass is nearly filled with Bordeaux, only a tiny drop of Chianti is acceptable.
Capacitive Load
Capacitive load decreases the slew rate of the signal, and eventually prevents the electronics to detect it correctly, and an I2C error occurs.
Capacitive load
== Induced Signal Disturbances ==,