dspic33ep512mu810 => Serial port connected with PC

[vallejera]

Dear all,

I am working with the DSPIC33EP512MU810 and I have this problem: I have tried to configure several times the chip for using the serial RS232 communication having an hyperterminal connected to the PC, but I don´t receive correctly the information. I receive something like this:

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I tried using a several very simple code like this:

[Gabriel]

probably wrong clock setup.... most likely your clock is running faster or slower than you think... and thus the baud calculation is off..

sometimes that is done purposedly like when changing clock speeds mid operation... in order to keep the same baud from the PC point of view if you half the PIC clock frequency you double the baud on the UART...

make a proper blinky test... use an O-scope if you have one...
_________________
CCS PCM 5.078 & CCS PCH 5.093

[jeremiah]

Your code indicates that you are using an internal oscillator of 16 MHz. I wasn't able to locate a 16MHz internal in the data sheet and you didn't specify using the PLL in your code.

Is there a 16MHz internal on that chip?

[rnielsen]

The link on Microchip's website:http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en554310 states it has an internal Oscillator of 7.37 MHz or 32.768kHz.

Ronald

[Ttelmah]

Yes. This is a very important thing to 'understand'.

The clock statement in CCS, historically was you telling the chip what speed you were running. Nothing else.

With latter chips, it became a 'double purpose' statement, with you telling the chip what speed you were running, _or_ if using sources with options available, telling the compiler what it should try to setup.

However what it 'can' do is always constrained by what the hardware can do.

Now on the PIC33, the internal oscillator cam be used with a complex PLL/divider chain, too generate a huge range of frequencies. However _only if this is enabled_. Hence Jeremiah's comment.

Without the PLL/divider chain, just two frequencies are available, and neither of these is what you are asking for.

It is a 'pity' that the compiler doesn't issue a warning in this case, but it does tend to assume you _know_ what you are doing....

If you get rid of the oscillator fuse (FRC), and just change the clock statement, to:

#use delay (INTERNAL=16MHz)

Then the compiler (on recent versions), will attempt to setup the clock for you. and will select FRC_PLL, with *35/16 = 16.12MHz, or *17/8 = 15.66125MHz. Without the PLL, the current code will be running at 7.37MHz, and hence the serial problems....

Best Wishes

[vallejera]

Dear all,

thank you for the information!! It has been very useful!!
Therefore, for working with the internal oscillator and using a frequency of 16MHz, I have to insert this lines in my code:


#include <33EP512MU810.h>
#use delay(internal=16120000)
#FUSES FRC_PLL //Fast RC with PLL


Do it need any other configuration?

[alan]

The #use delay should set all the correct fuses. Have you checked that your clock are running at the speed that you set as was mentioned earlier.

Regards

[vallejera]

Now it is working fine!!!
Thank you very much for your support!!!!