I’m trying to get a DS1307 RTC working. I’m using the seeed grove board (https://www.seeedstudio.com/Grove-RTC-p-758.html) on a sensors mezzanine (https://www.96boards.org/product/sensors-mezzanine/) so its a plug and go setup.
Other i2c devices I’ve plugged in work fine (i2cdetect -y -r 0 or -y -r 2). However, this one is only detected occasionally. The difference that I can see in the spec is that the DS1307 is limited to 100 kHz, whereas everything else I’ve tried is 400 kHz.
I have changed to 100000 here; https://android.googlesource.com/kernel/hikey-linaro/+/android-hikey-linaro-4.9/arch/arm64/boot/dts/hisilicon/hi3660.dtsi#426 or here; https://android.googlesource.com/kernel/hikey-linaro/+/android-hikey-linaro-4.9/arch/arm64/boot/dts/hisilicon/hi3660.dtsi#568
Before I hook it up to a probe, is there anything else that should be needed to get the i2c running at 100 kHz? Or is there any known issue with that rate? Has anybody actually used a 100 kHz device on this board?