SCL is the I2C clock signal and not a data line. It oscillates for timing data and would show a constant voltage wirh a multimeter. You woukd need an oscilliscope to see the clock signal. The clock doesn’t toggle state it oscillates. I2C is not designed to directly turn a relay on or off, it is designed to commumicate with I2C ccomponents that would turn the relay on or off.
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is it possible to recover the original firmware of the motherboard?
In the first post, there is a link to what he’s using as a guide, it uses the SCL line to control a relay for air assist. I have to assume they are not using this as a I2C port, just an i/o pin that’s externally accessible…
I haven’t worked with these too much, but I doubt that the I2C port is active by default. I read 0V after mine boots. It doesn’t appear active and I wouldn’t expect it to read anything. The I2C specifications expressly states it has to have a external pullup resistor. This has no such resistor that I know of…
Again, I don’t really know these boards or processors very well…
I just took the measurements on the different terminals:
3.3v/G = -3.3v
SCL/G = 0v
SDA/G = -3.3v
SCL/SDA = 3.3v
no change with M7 or M8
SCL/GND Probe = 3.3v
S/GND Probe = 3.3v
5v/GNG Probe = 5v
rumback = 3.3v
no change with M7 or M8
Well, I’ve been working with processors and communications for 50 years. As I said, this is a Zerial CLock (SCL) Only line. Jt provides a clock only from the ARM processor either through clock divider. The data line can have either an internal or external pullup resistor, not the clock. Again, the serial clock is used to clock the serial data on the SDA line. But there is much more to the protocol which you can learn from book Embedded Systems Desktop Communications (2004 Wordware Publishing) available on Amazon.
Thank You.
Note that this board uses an ESP32.
Not following what you mean by this. Both SDA and SCL require pullup resistors. Note from Espressif documentation:
@berainlb, right… not an arm processor.
The processor type, like ARM has nothing to do with the I2C protocol, it’s just a communication protocol. Created in the early 80’s by Phillips.
Yes, the hardware requires pullups… it’s literally open collector/source.
What I’m trying to say is that this probably has nothing to do with I2C configuration…
I have not worked with the ESP32, but reading the documents, it’s much like many other small machines. I’ve worked with a number of micro controller. Few pins are not programmable. This pin is referenced as just another i/o pin…
I’m saying they are not using it as SCL, it’s just labeled that way on the board…
@killrob is apparently using it like this from the first post link, so I expect it does work…
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