"Failed to write to i2c port for write" with cpp demos

Hello, I was able to get the demo-adcspeed python program to run without any difficulties but, when I attempt to get the C++ demos to run, I consistently get an "Failed to write to i2c port for write". I did 'sudo apt install libi2c-dev' and, when I run 'i2cdetect -y 1' I see the adc on address 20... I am stumped... any pointers? Thank you.

UPDATE: after posting my question, I noticed that 'sudo i2cdetect -y 1' showed UU in address x68; aparently this indicates that address is unavailable for user application. Since I had done the rtc set up, I figured this was then due to the hwclock being in operation so, I backed out of this by undoing the edits. With hwclock not operational I have the 68 showing for that address on i2cdetect and, now the cpp demos run. To me this looks like I cannot use the rtc (as hwclock) _and_ use the cpp implementation of the adc.... does this seem correct?

Hello

The Expander Pi library tries to write to the RTC when it initialises the object. As the RTC was locked by the hwclock module this was blocking access to the I2C address and causing the code to fail.

I have updated the Expander Pi library with a new "usertc" parameter in the ExpanderPi function so setting the parameter to false it bypasses the RTC initialisation and allows the code to work correctly. You can download the updated library from our GitHub repository at Expander Pi GitHub Repository

When you create an ExpanderPi object you will need to pass in values for the initialise and usertc parameters. For example,

ExpanderPi expi(true, false);

Hopefully, this will fix the problem you are having and allow you to use the ADC when the hwclock is operational.

Wow! Thank you for the quick response and resolution! That is great support!!