Hi @Di ,
yes you are right. The BlueTile core is a BLUENRG-2 chip that has an embedded differential ADC (ADC1 and ADC2 pins), although only ADC1 is connected to the external world on BlueTile, being especially designed for single-ended analog microphone (such as the MP23ABS1 MEMS microphone) acquisition and system integration.
You can connect an external analog signal, but not sure you are able to plot it on the ST BLE Sensor app: sure however you can manage it in the standard debug mode via the STM32CubeProgrammer and the ST Link connected to the ARM10 connector.
In case you have time, you may implement the ADC BLE characteristics from the ST BLE Sensor source code on Github (HERE), even if I'm afraid it is not so straightforward...
-Eleon
