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Post by lbendlin on Jan 28, 2019 7:42:58 GMT -8
What is the relationship between the VDDM pin on the I2C bus and the JP4/1 pin ?
I am trying to power JP4/1 from the SunControl VDDM pins. The SunControl is also on the I2C bus via the Grove connector. I seem to sporadically lose 0x21 on the I2C bus, maybe because there is some voltage mismatch/circuitous situation going on?
Is the SunControl powering the I2C bus, or is it passive? In other words, of my various devices attached to I2C, which of them is providing the bus power?
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Post by SDL on Jan 29, 2019 10:21:56 GMT -8
Not ignoring you. I just need to be back in the office to answer this.
BP
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Post by lbendlin on Feb 1, 2019 11:43:44 GMT -8
thank you. Looking forward to your findings. Just had the QPM drop off the I2C bus again, right when i would have needed it to disconnect my solar panels..
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Post by lbendlin on Feb 2, 2019 8:19:13 GMT -8
I have to say I am underwhelmed by the QPM. I really thought this would be the best solution (and I _love_ the screw terminals!). However the QPM interface does not programmatically understand the status of the GPIOs until _after_ it wrote to them (like a consultant, basically, who asks you for your data and then sells it back to you), and it is very susceptible to overvoltage. Anything over 5.3V makes it disappear from the I2C bus.
It's a shame really as the QPM is the only I2C relay board on the market that has completely independent channels. Other Solid State Relay boards have common rails for ground AND supply voltage which is not appropriate for my setup.
I tested that too, and it looks like the SunControl provides VDDM to the I2C bus. I know that at the same time the Raspberry Pi provides that power to the i2C bus as well. Not sure if that's a problem but it certainly makes me think. What if I had chosen to use the 3.3V on the Pi to power the i2C bus?
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Post by SDL on Feb 3, 2019 13:55:36 GMT -8
Lutz,
SunControl does not power the JP1/3 pin. That is for an external I2C bus coming into SunControl. It has a 3.3V /5V translation circuit.
I am trying to power JP4/1 from the SunControl VDDM pins
VDDM pins? On SunControl? What pins are we talking about here. The VDD5 pins? Or are you talking about the QPMB VDDM pins.
On the QPMB board, VDDM is connected directly JP2/1 which is input power for the QPMB board.
However the QPM interface does not programmatically understand the status of the GPIOs until _after_ it wrote to them (like a consultant, basically, who asks you for your data and then sells it back to you),
and it is very susceptible to overvoltage. Anything over 5.3V makes it disappear from the I2C bus.
Overvoltage on what pin specifically? The FDC6330 has an input spec of 3V to 20V and 2.5A
I *suspect* that you have some kind of a power glitch on the JP2/1 caused by you shutting off the solar panels. Adding a big capacitor from JP2/1 to Ground will probably fix that.
That would explain the QPBM board dropping off the bus. I've used this board successfully in almost exactly the same configuration.
BP
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Post by lbendlin on Feb 4, 2019 4:43:14 GMT -8
I was referring to the overvoltage on the QPM VDDM (which comes from the SunControl VDD5, either via jumper or through the J7 I2C Grove connector. I am not currently using J1 on the SunControl. Maybe I should, instead of the Grove I2C (J7). Would that eliminate the dual sourcing of the I2C VCC? I guess that's back to my original question - what happens if multiple hosts provide power to the I2C bus?
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Post by lbendlin on Feb 6, 2019 10:37:01 GMT -8
I tested this by removing the power pin from the cable going into J7. Contrary to what I had feared, the power pin on J7 is incoming, not outgoing. The SunControl board disappeared from the I2C bus when the pin is disconnected.
That's a relief. Maybe it is worth mentioning that more clearly in the SunControl documentation.
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