The biggest mistake beginners make is connecting the JDY-40 to Serial (Pins 0/1). This clashes with the USB programmer and crashes your uploads.
The is a low-cost, ultra-low power wireless serial pass-through module based on the CC2541 chip. It is often preferred over the older HC-05/HC-06 Bluetooth modules because it supports both Bluetooth 4.0 (BLE) and standard serial transparency, and it requires no complex AT command pairing process for basic data transmission. jdy40 arduino example best