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I2C and Raspberry Pi5
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2024-02-24, 03:48 AM
Has anyone else noticed that the Pi5 does not seem to be as good as the Pi4 with I2C? It seems not to tolerate much more than about 200 mm of a wire run or a large number of devices. As I added more devices the length of the run needed to be shorter.
Adding an Adafruit LTC 4311 Active I2C terminator resolved the issue. 
2024-02-25, 06:14 PM
(2024-02-24, 03:48 AM)Opie91 Wrote: Has anyone else noticed that the Pi5 does not seem to be as good as the Pi4 with I2C? It seems not to tolerate much more than about 200 mm of a wire run or a large number of devices. As I added more devices the length of the run needed to be shorter. Great info, Thanks Just curious, what devices are you running?
2024-02-26, 11:11 PM
Running MPU9250, ADS1115, INA3221 and BME280.
Everything I read here and on other forums says not to expect much out of the I2C for distance but never had a problem before. The LTC 4311 seems to make a big difference and it doesn't break the bank.
As a quick fix for electronics tinkerers, adding extra pull-up resistors to SCL and SDA may also resolve I2C issues.
Typically, I2C sensor boards have on-board resistors. But they may be too weak (large resistance value) for long wires and/or faster bus speeds. Adding pull-up resistors from the I2C lines to 3.3V will reduce the total pull-up resistance (more resistors in parallel), making the pull-up speed faster. I'd start with adding 4.7kohm, and if that doesn't work try 1k. I wouldn't go lower than that. The technical background is explained in this video: https://www.youtube.com/watch?v=n2eaY51rkJQ |
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