Hello, I want to build battery powered modules (with sleep). I found on Ebay NRF51822 round module with case (https://www.ebay.com/itm/hello/112650665753) - only $6.50 with shipping. Is this module is good choice? Any pitfalls?
I planning to use water leak sensor, BME280 (I2C), ds18b20(1-wire), maybe MH-Z19 later.
I don't have enough experience, I have only used ESP8266 NodeMcu V3 and Arduino before.
I can see one I2C (for programator and sensors?) and one GPIO as button for water leak (right?) + LED pin. Does this module have more pins? Shall I connect to chip legs to obtain more pins (GPIO) (does I need to connect resistors?) for 1-wire or better use some sort of I2C GPIO expander?