On Thu, Sep 7, 2023 at 9:47 PM Lucas Tanure <tanure@xxxxxxxxx> wrote: > > > > On Thu, 7 Sept 2023, 14:56 Russell King (Oracle), <linux@xxxxxxxxxxxxxxx> wrote: >> >> On Thu, Sep 07, 2023 at 08:36:32PM +0700, Bagas Sanjaya wrote: >> > [also Cc: devicetree and ARM folks] >> > >> > On Thu, Sep 07, 2023 at 08:21:44AM +0530, Raul Piper wrote: >> > > Hello , >> > > I am trying to detect an i2c device A on i2c1 line on one of the Arm >> > > Cortex A7 platform but not able to see any device on a given address ( >> > > 0x3d) . >> > > >> > > Is there any parameters of i2c which i can change like rise/fall time >> > > , timeout etc in a device tree or kernel source and re test it? >> > > I have tried changing the i2c speed from 100KHz to 400 KHz but no success. >> > > I have even tried removing the 1.5K pull ups on the i2c lines but no result. >> >> Honestly, from this description, I'm wondering if this posting is a joke. >> >> I2C is entirely _reliant_ on pull-ups. It's a wire-or bus, and the >> logic 1 state is created by no device pulling the signal low, thereby >> allowing the pull-up resistor to pull the line to the logic 1 state. >> >> The pull-up must be the correct strength for the devices on the bus. >> If it is too strong, then a driver may not be able to pull the signal >> sufficiently low for other devices to register it as a logic 0. >> >> Conversely, the pull-up must be strong enough so that the rise-time >> of the signal is sufficient to register as a logic 1. >> >> If it's a problem with the rise time, then increasing the clock rate >> will just make the situation worse. Where can I change this time? Can you please provide example of some device/device tree? >> >> So, if other devices work on the bus, it could be that the Vil >> threshold of this device is not being achieved, whereas the other >> devices are happy. Therefore, I would suggest you study the data >> sheets of the device that isn't being detected. What Vil threshold? I checked the power supply to this device and it is ~3.3 V as expected. >> >> Lastly, if the undetectable device has a reset line, it's possible >> that the device isn't responding because it's being held in reset. The device is fine, I am sure about it. As the device provides data on USART as well and I am getting it. > > Please try to use an logic analyser like saleae logic. > Probe the i2c bus, reset line, power lines, pins that set the i2c address for the device. > Can tell us which device it is? Its a GPS sensor(still under development) .Logic Analyser gives NACK on the given address. I may be using the wrong pull ups value which i am checking.But from software point of view is there a Device tree setting to enable the internal pull ups or adjust the rise/fall time as said above. > > > >> -- >> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ >> FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last! >> >> _______________________________________________ >> Kernelnewbies mailing list >> Kernelnewbies@xxxxxxxxxxxxxxxxx >> https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
