I use a raspberry pi model 3. I did all of things according to this link:
http://www.instructables.com/id/Read-an ... pberry-Pi/
using a usb-serial converter (PL2303), I connected it to pc and using Putty terminal set to 9600-8N-1 use the c code in the following link in raspberry:
http://www.raspberry-projects.com/pi/pr ... g-the-uart
But the write() function in c code always retun 0. Can you help me? Open() function return fd=3.