When I use UART communication between Arduino and other UART devices, I get these problems:
I can not upload program into Arduino when its UART pins are connected with any other devices. I can only upload the program after I plugged out those UART pins. (Some body tell me it's common and isn't a error)
After I upload the program into Arduino, I reconnet, turn it on but it doesn't work. (I can also make my Arduino work by turn it on when the UART pins are plugged out, then I plug them in after Arduino is turned on)
It doesn't work, so I reset it, but it doesn't either. And like the first problem, I have to plug out all UART pins in order to reset it, it is reset, but then I have to plug in those pins again to make it work.
Can anybody tell me if I did wrong? My hardware isn't good or somethings? And how to fix them. Thank you.
p/s: Please also spot any my English misstake.