UART RX Problem

arunkish · Joined: 23 Dec 2008 Posts: 83

Dear All,
I am having a problem with UART. I am using 18F4620 clocked at 4 Mhz. uc hangs when it receives serial data sent from another uc. I also used getc, but still I don't have any progress. I have completely checked the hardware on both sides. I can read the serial data in PC sent from the other TX controller. Likewise my receiving controller reads the data when sent from the PC. But if I connect both controllers, it hangs and sometimes it receives junk characters. Please advise.

bkamen · Posted: Fri Apr 01, 2011 11:57 pm

That's your whole program?

How can that compile with no main()??
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Dazed and confused? I don't think so. Just "plain lost" will do. :D

arunkish · Joined: 23 Dec 2008 Posts: 83

That's not my whole program. I have just given you the section of code.

Ttelmah · Joined: 11 Mar 2010 Posts: 19343

Key thing that is wrong, is what int_rda does....

You need to understand what INT_RDA implies. It triggers when _one_ character is ready to be read from the serial. The handler need to do just one thing. Read this character. This is _all_ it should do, and what it _must_ do.
Your INT_RDA, does not read the character. Unless it does, the code will hang for ever, looping back to the interrupt as soon as you exit the interrupt.
Instead your INT_RDA code, writing 8 characters to the LCD (and clearing a screen line, which takes even longer).
Look at the EX_SISR. c example, which shows what an INT_RDA, _should_ do. save the characters, so that the external code can use them when _it_ is ready to.

Best Wishes