dsPIC33F UART, strange behaviour, timing problem?

[sth_tob]

Hello there!

Someone could explain me, why the behaviour of the following code is, that the LED toggles every 1 second, but the printf(char *) function doesn't send my desired string to the UART1 in same time intervall?

First i thought there's some timing problem, because the 7.37MHz are maybe not OK for the 9600 Baudrate. But that's not the reason i guess, because my UART receiver (RS232 serial port) receives only correct strings!

Here's a test code that demonstrates the behaviour. Does sequential code execution happens here? Or does the compiler automatically decides to "skip" printf(char *) statements? I can't imagine that the "send string functions" isn't fast enough to execute within that 1000ms loop. If i remove the delay_ms(1000), my RS232 console gets an excessive amount of strings, more than a whole console window within a second!!

[sth_tob]

I'm using a MAX3232 level converter. I think it's damaged . It has 2 channels and 1 channel doesn't work, while the other have this "just sometimes send" behaviour. Also, it doesn't even work with recommended 100nf capacitors, i had to use at least 1µF to get some RS232 output.

[Ttelmah]

Have you got all five capacitors. They are all required (including the one on the incoming 3.3v rail). The test circuits all show this, but they then refer only to the ones forming the actual charge pump (4 capacitors). Unless the source impedance of the supply is very low, the fifth capacitor on the incoming rail is just as important....
Check the voltages on pin2, and pin6. You should have about +/- 5.5v here.