Mismatched receive data using UART on dsPIC33CH512MP505

Hello together
 
I have a simple UART program, generated with code configurator. Test program receives data and sends same data back to transceiver. 
 
My Problem
If two or more bytes are sent from PC to the dsPIC33 at the same time, the receive data are mismatched. 
 
Device settings
Internal oscillator
Baud rate 9600 bits/s
 
I checked
Data directly on Rx input pin are good (with oscilloscope)
Signal shapes look fine
I wrote a test program that writes 4 characters at the same time continuously form dsPIC33 to PC. All data are fine. So the transceiver should work correctly.
Tested on two different IOs and UART1 and UART2. Same situation
Tested with two different RS232 transceivers (Silicon labs) and ESP32 controller. Same situation.
If I send on byte per second, the program works fine.
If I send e.g. 0xAA 0xAB the dsPIC receives data 0xAA 0xF5 (see attached picture).
The program uses input buffers with Rx and Tx-Interrupt but the problem also occurs if polling is configured in code generator.
Testes input data with ICD4 debugger. Data mismatched
 
Thank you for your help
 
Geri
 

Hello 
 
"How did you setup the oscillator ?  internal / external ?"
internal oscillator
 
What is Fosc in your system ?
8 MHz
please see attached picture.
You can also see the PLL-Settings in the attached picture before
 
did yu compute the error on the baud rate ? 
Baud rate error is 0,006%

Can you attach you zipped project?
 I was not able to upload it here. I can only uploads pictures, no zip file -sorry
 
 
Best regards and thank you
 
Geri

Hi,
It is possible to upload many types of files but first push "Open full version" just above.
I don't think you use Fosc = 8MHz....unless you did not activate the PLL. 8MHz is the internal oscillator frequence Frc
This device can run Fcy = @90MIPS i.e. Fosc = 180MHz.
It is not so simple to setup oscillator registers...I used MCC a couple of weeks ago to generate the code to achieve Fosc = 180MHz with dsPIC33CH512MP508.
My setup is shown on the attached image
Regards
 

Oh as for what is wrong my guess is the transmitter is 1 stop bit the receiver 2 ... which is why the second character is wrong :-)

Maybe the PIC is configured for two stop bits.
What value has been written to the UxMODEH register?
 

Checked the errata: might really be a stop bit problem as there's an error that won't raise an FERR (due to the 2-stop violation).
Re-reading the scope with this assumption makes or a perfect 0xAA 0xF5.
Sending some more characters without pause would unveil more "weird things". Writing appropriate characters could even raise FERR.

Good morning together
 
Thank you all for your help. I tried your hint with the two stop bits and now the program is working.
So for all having similar problem, a change to 2 stop bits could helps.
 
However, I checked the UART settings and it should be OK. I attached a screen shot of the UART init procedure. The example code was fully be created using the MC code configurator.
 
I again tried to upload the full project for your information but I still can only upload gif, txt, jpga are supported. What I am doing wrong?
 
 
@du00000001: Regarding the errata sheet:
I studied the document but as I saw, a problem should only occur if:?

6. Module: UART When the UART is operating with STSEL<1:0> = 2 (two Stop bits sent, two checked at receive) and STPMD = 0, the FERR bit will not get set if one Stop bit is received.

http://ww1.microchip.com/downloads/en/DeviceDoc/dsPIC33CH512MP508-Family-Silicon-Errata-and-Data-Sheet-Clarification-DS80000805D.pdf
 
 
Thank you 
 
Geri
 
 

Hello
 
Thank you Risc.
Attached the zipped MPLAB-project
 
Best regards
Geri

256K, 7 x data, 1 x stop, xon.
Running 2 x uarts (next to I2C)
 
btss    U1STAH, #UTXBE
bra     $-2
mov     ch, U1TXREG
 
Instead of checking when full, check when empty.
(sending)
 
A 100nF near the power pins for each uart will keep
it stable all Day @256K.
 
Configure uart with fraction divide.

Set the PIC to receive 1 stop bit, and the PC to send 2.