Hello I’m getting mixed results on how far of length I can go for spi and i2c? My project I need to go 3ft for spi and 1.2ft for i2c is this possible? Joseph

SparkFun QwiicBus - EndPoint [image] SparkFun QwiicBus - EndPoint - COM-16988 - SparkFun Electronics The SparkFun QwiicBus EndPoint is the fastest and easiest way to extend the range of your I2C communication bus.

[image] josephchrzempiec: how far of length I can go for spi and i2c? It depends on a lot of things but the two most important is the speed of the data and the capacitance of the wire. With SPI it is easy to set the speed of the connection, so if you are having trouble try slowing it down. W…

Hello all, thank you for responding back. I two sensors on i2c for temperature and the spi I have a Ethernet module. Because of the limit space I have to run the Ethernet module apart from the rest. Joseph

I have successfully tested I2C over 20 meter with a 4x twisted pair cable. GND+SDA in one pair, GND+SCL in the second pair (the other two pairs was not used).

[image] thehardwareman: 4x twisted pair cable. GND+SDA in one pair, GND+SCL in the second pair Just about the worse thing you can do with I2C as that increases the capacitance of the connection and that is the critical thing. What were your pull up resistor values?

If doing long runs with high speed clocked logic busses like SPI, its wise to add small series resistors at each end to the signal wires, 68 to 100 ohms sort of value. This should reduce the risk of signal reflections causing a double-edged clock transistion, and reduce overshoot spikes. SPI in pa…

[image] Grumpy_Mike: Just about the worse thing you can do with I2C as that increases the capacitance of the connection and that is the critical thing. The above keeps capacitance to ground of both lines the same (~53pf/m for Cat-5/6), and cross-talk between SDA and SCL minimal. Twisted (or…

[image] Wawa: The above keeps capacitance to ground of both lines the same That is not an issue. [image] Wawa: Please tell us how you would do it, without using extra hardware. I would use non twisted pairs of connectors with pull up resistors pulling 2mA instead of the normal 1mA. Bu…

[image] thehardwareman: I have successfully tested I2C over 20 meter with a 4x twisted pair cable. GND+SDA in one pair, GND+SCL in the second pair (the other two pairs was not used). I2C Bus is designed for the I2C devices to be wthinn a board of around 12 in x12 in. You are operating the dev…

What is the length that I can go for spi and i2c?

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claude_j_greengrass September 27, 2021, 1:37pm 2

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What is the length that I can go for spi and i2c?

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