About serial of raspi

[zhanghaijason]

Hello, I tried Gordon's example code serialTest.c to test my serial. But it only worked once and the output is ''-1 -> -1 ->-1 ->-1 ->-1 ->-1 ->-1 ->-1 ->-1 ->-1 ->" something like that. But only worked once. Then when I run 'sudo ./serialTest', there is no output on the screen. Could anyone give me any suggestion to solve it?
Thanks and regards

[B.Goode]

Could anyone give me any suggestion to solve it?

Probably not without some basic facts to start from...

For example -

What Operating System have you installed?

Who is Gordon?

Where did you download serialTest.c?

What hardware and cabling are you using to create a serial port connection?

[zhanghaijason]

Could anyone give me any suggestion to solve it?

Probably not without some basic facts to start from...

For example -

What Operating System have you installed?

Who is Gordon?

Where did you download serialTest.c?

What hardware and cabling are you using to create a serial port connection?

Sorry that I gave too little information.
OS is NOOBS, Gordon is the person who writing a library named wiringPi in C. the serialTest.c is from the library's examples. I just connected the TXD and RXD of the raspberry A+

[jlopez2022]

Did you give some time delay between write and read at the port?
The writing speed of the port is not unlimited, so perhaps you tried to read before words are written

[DougieLawson]

Have you disabled the serial console on /dev/ttyAMA0? There's an option in sudo raspi-config to do that.

[zhanghaijason]

Did you give some time delay between write and read at the port?
The writing speed of the port is not unlimited, so perhaps you tried to read before words are written

Yes, there is a 'delay' in the codes. I think it's not this reason

[zhanghaijason]

Have you disabled the serial console on /dev/ttyAMA0? There's an option in sudo raspi-config to do that.

Thanks for your reply first. It worked once again and continued to fail. I guess it may be the enable and disable serial console. But even I enabled the serial console as you told me. It still failed.

[DougieLawson]

The usual cause of serial comms failures is mis-matched baud rates. Make sure you've got the same baud rate at both ends and 8,N,1 for bits, parity and stop bits. It's a good idea to start with 9600,8,N,1 as most equipment can run at that speed.

[zhanghaijason]

The usual cause of serial comms failures is mis-matched baud rates. Make sure you've got the same baud rate at both ends and 8,N,1 for bits, parity and stop bits. It's a good idea to start with 9600,8,N,1 as most equipment can run at that speed.

I figured out that there is something wrong with my SD card. I tried a new one and it worked. Thank you again.