UART - strange behaviour when com speed increase

Hi,
in my personal project I connect an Arduino Pro Mini 3.3V 8MHz to a D52QD2M4IA module (D52 ANT SoC Module Series | Dynastream Innovations).

According to datasheet and wiring indication, I connected the Arduino and the D52Q module by UART serial port. By Arduino side I used pin 8 and 9 for soft-serial port. Pin 8 for TX and 9 for RX connected to D52Q module in this way: pin 8->211 and pin 9->212. By wire I selected on D52Q module a speed of 9600 (BR1=+VCC, BR2=GND, BR3=+VCC). All works fine. I can exchange all data from and to module without any kind of problem. But if I try to increase UART speed setting by wire (BR1=GND, BR2=+VCC, BR3=GND) adjusting setting for Arduino, born problmes! I do not receive correct packages, seem they are corrupted.
I need to increase speed at least to 57600 to obtain the correct data flow to manage my project requirements. I checked D52Q datasheet and it can reach 115200 on UART port.
What can I do to obtain my target?
Many thanks to all!

In my experience Software serial will work, reliably, at 38400 baud and no faster. You have a couple of choices. Get an Arduino with more than 1 hardware serial port (Mega 2560 for instance) or use the Mini hardware serial for communicating with the D52Q and a USB to TTL converter connecting the Mini with Software serial to the PC for debugging. You will have to swap ports (disconnect the D52Q and connect PC to hardware serial) to upload code.

Or use AltSoftSerial. Much more reliable and efficient than SoftwareSerial!

groundfungus:
In my experience Software serial will work, reliably, at 38400 baud and no faster. You have a couple of choices. Get an Arduino with more than 1 hardware serial port (Mega 2560 for instance) or use the Mini hardware serial for communicating with the D52Q and a USB to TTL converter connecting the Mini with Software serial to the PC for debugging. You will have to swap ports (disconnect the D52Q and connect PC to hardware serial) to upload code.

Ok.
Assuming I choice to change the MCU from Arduino Pro Mini 3.3V 8Mhz to an Arduino Mega 2560 5V 16MHz so I can use hardware serial ports to connect both PC (via USB/TTL PL2303 converter) and D52Q.
The main question here is the logic level voltage because Arduino works at 5V and D52Q works at 3.3V ONLY! So I can power up D52Q with 3.3V out pin from Arduino, but my question is: Can I connect Serial1 (pin 18/19) directly to D52Q UART port? Or I will risk a D52Q UART burning?

/dev:
Or use AltSoftSerial. Much more reliable and efficient than SoftwareSerial!

You could have provided a [u]LINK[/u] to it at least......

akard:
Ok.
Assuming I choice to change the MCU from Arduino Pro Mini 3.3V 8Mhz to an Arduino Mega 2560 5V 16MHz so I can use hardware serial ports to connect both PC (via USB/TTL PL2303 converter) and D52Q.
The main question here is the logic level voltage because Arduino works at 5V and D52Q works at 3.3V ONLY! So I can power up D52Q with 3.3V out pin from Arduino, but my question is: Can I connect Serial1 (pin 18/19) directly to D52Q UART port? Or I will risk a D52Q UART burning?

To interface 3.3v stuff to 5v, I use either a simple series resistor (for "low speed" connections) or a 2 resistor divider for high speed connections (that is, a series resistor or a divider for EACH 5v to 3.3v link).

I'm sure some "expert" here will try to tell me why it doesn't work, but believe me... it does work and it's simpler and easier (and less expensive) than level shifter circuits.