I use Mountaineer Ethernet board with i2c sensors:
Grove BMP180 + SHT21
And first of them have pullup resistors, second - I tink too. But Chronodot - does not have pullup resistors. And for two or three days all works normally, but after that time, the device stopped working with the i2c bus. After that I connect only one HP206C to my Cerbesur controller - it works correct.
So… the question is: could I break down the i2c bus on my Mountaineer Ethernet board? If so, how do I make sure to not to break my cerberus board?
really, you only need one set of pullup resistors on I2C. The reason is that the device on the bus needs to drive the signal to low. If you’re adding multiple devices and they have their own pullups, you may be influencing their effectiveness. I just found this article that talks about different impacts on the signal. [url]DssCircuits.com is for sale | HugeDomains Fundamentally, you shouldn’t break anything by having multiple pullups on the line.
From the mainboard builders guide, it states:
For socket type I, mainboards should include I²C bus pull-ups of 2,200 Ω on both SDA and SCL pins. Modules must not include pull-ups on these lines.
So my suggestion would be - ditch the onboard pullups off your modules.
For socket type I, mainboards should include I²C bus pull-ups of 2,200 Ω on both SDA and SCL pins. Modules must not include pull-ups on these lines.[/quote]
According to the schematics neither the Mountaineer nor the Cerberus do not have these resistors
So… I need them at least on one sensorboard.