[PIC] problem with reset for uart tx

[bhagavanec67]

Hi every one,

I am facing a problem with reset of my DSPIC33FJ128GP802 controller board. I am try transmit data 0x31,0x32,0x33,0x34 using uart. my problem is when I dumped the programm using ICD3 intially it showing 82 9F etc which are irrelevant. But upon reset it shows the correct values. I am using a Comport software I am facing the same problem with that if I Close and open the com port. please help me for this.

The board is designed as per the references.

Thanks.

 

[Aussie Susan]

There are two things that come to mind that would fit your very brief description of the issue:
1) the BAUD rate is mismatched between the MCU and the PC com port; when you close and reopen the com port, it may be starting up with the wrong setting
2) the MCU oscillator is not being given enough time to stabalise before you start to send characters and therefore the characters are at the wrong BAUD rate; however this should sort it self out very quickly once the oscillator settles down.
Are you able to successfully send characters the other way (from the PC to the MCU)?
I'm not sure what you mean by "...dumped the programm[sic] using ICD3..." - does this mean that you tried to program the MCU through an ICD3; that you were trying to examine the program code by getting the ICD3 to transfer the program memory to your PC; or that you were using the ICD3 to debug the code. Further, I'm not sure what this has to do with your problem of not receiving the correct characters.
Susan

 

[milan.rajik]

Is your dsPIC33 a 3.3V device ? How have you interfaced dsPIC33 to PC ? Using MAX232 or TTL2USB converter ? If TTL2USB converter, does the TTL level of adaptor is 3.3V ? If TTL level of TTL2USB adaptor is 5V then you will damage the dsPIC33 UART pins.

I use this TTL2USB adaptor.

**broken link removed**

It has option to select 3.3V or 5V TTL voltage.

 

[bhagavanec67]

Thanks for your reply. we too thinking of the same reason1 mentioned in your reply. Would you help me hoe to over come this.

- - - Updated - - -

we have max on our board to translte the logic. We are using 3.3V icd3 which is suitable for our MCU.

 

[Aussie Susan]

On the PC side of things I can't really help as I don't know the Comport software. However there is typically a section where you can configure the serial port as to the baud rate, number of start bits, parity etc..
On the MCU side the things that impact the baud rate are the oscillator settings and the BRG setting for the UART. Perhaps if you can show us your code in these areas and tell us the baud rate settings you intend, then we might be able to spot an issue.
Susan