What is the problem? Please be detailed.
I cannot create a form with a string variable that can take input more than 255 characters. Either it is text or varchar, any input more 255 character is getting truncated. Is there any way to input string/text data more than 255 characters in a single field?
What ODK tool and version are you using? And on what device and operating system version?
What steps can we take to reproduce the problem?
What you have you tried to fix the problem?
Anything else we should know or have? If you have a test form or screenshots or logs, attach here.