STM32F103 - internal temperature sensor ADC doesn't change value
You channel selection is wrong. In the ADC_CR1, you can enable analog watchdog on the selected channels. But it does not enable the channel itself only the watchdog, Page 240.



To select a channel you must use ADC_SQRx or ADC_JSQR registers, depending wether regular or injected group is needed, Page 218.