Maybe this will help someone struggling with setting up Arduino Mega2560 with HM-10 Bluetooth module.

I bought my Bluetooth module from Amazon and apparently it seems to be 'clone' even though it has the Texas Instruments CC2541 chip, which is used in the original module from Jinan Huamaoand(?). I did not have to upload original firmware to get this module to work.

I started experiment with 4ntoine mega-to-hm10 repository to setup the connection.

Unfortunately pins TX14 & RX15 or TX18 & RX19 did not work for me.

Had the same issue like many others have had with AT commands not working in serial mode.

It seems some documentation is inconclusive within Arduino website about RX pins?

Within SoftwareSerial library documentation it is stated:

• Not all pins on the Mega and Mega 2560 boards support change interrupts, so only the following can be used for RX: 10, 11, 12, 13, 14, 15, 50, 51, 52, 53, A8 (62), A9 (63), A10 (64), A11 (65), A12 (66), A13 (67), A14 (68), A15 (69). Not all pins on the Leonardo and Micro boards support change interrupts, so only the following can be used for RX: 8, 9, 10, 11, 14 (MISO), 15 (SCK), 16 (MOSI).

And within SoftwareSerialExample it is stated:

• Not all pins on the Mega and Mega 2560 support change interrupts, so only the following can be used for RX: 10, 11, 12, 13, 50, 51, 52, 53, 62, 63, 64, 65, 66, 67, 68, 69

My solution was to use pin 10 for RX. I assume that pind 11, 12 and 13 would work also.

Example code for testing serial mode and AT commands can be found within at.ino file.

I am beginner with Arduino. Hence, it is possible that due to my own mistake I did not get RX to work with other pins, eg. 15 or 19 in the beginning.