baud rate problem on pro mini 5v 16Mhz

Other Hardware 3rd Party Boards
1

Hi

This is my first post here so I hope it is in the right place.

I have a sparkfun serial LCD display and a simple program that works ok on the UNO but on the pro mini displays garbage.

My research leads to me to think that it is a serial port baud rate problem related. The link below seems to describe the problem exactly and provides a solution that, unfortunately, does not work. I copied in the modified HardwareSerial.cpp and HardwareSerial.h but nothing would compile so I put it back to the originals.

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1245508129

It seems to me that this is a well known problem and since I am running arduino 1.5 I thought it had been solved.
I'm at a loss on how to solve this problem.
regards
Grant

2

There are two version of the Pro Mini. One runs at 3.3V and 8 MHz, the other at 5V and 16 MHz.

Which one do you have?

3

Hi Nick

I have the 5volt 16Mhz version.

I have made some progress = workaround. By setting the baud rate to 19200 it works ok even though the display is at 9600 baud.

My next problem is with the DallasTemperature one wire library and I suspect it is the same problem. A ds18b20 works fine on the uno but will not work on the pro mini. I updated the dallas library to the latest but this has made no difference.
I have tried both powered and parasitic mode. Both ok on UNO - both no sensor found on the pro mini.

Have I made a mistake buying these little ones ? Is there a systematic problem with the clock speed and libraries ?

I'd like to use it if I can.

Any help appreciated.

kind regards
Grant

4

I'm wondering if it is actually running at 16 MHz if doubling the baud rate fixes the problem.

5

You are so smart.

I got out a magnifying glass and checked the board. It is 3.3v 8Mhz.

I checked the order and shipping note - both say 5v 16Mhz. So there ya go. They sent the wrong thing. I did not even check that because we only buy 5v stuff.

Thanks a lot. One for the books.

regards
Grant

6

grantm009:
You are so smart.

I got out a magnifying glass and checked the board. It is 3.3v 8Mhz.

I checked the order and shipping note - both say 5v 16Mhz. So there ya go. They sent the wrong thing. I did not even check that because we only buy 5v stuff.

There's no reason it won't run at 5V if you bypass the on-board regulator (ie. put 5V directly to the Vcc pin). You're stuck with the 8MHz though.

7

So...

I recompiled everything for a 3.3v 8Mhz and voila it all started working. The only draw back is that my LCD units are 5v so I have ordered a 3.3v LCD and in the meantime providing 5v separately to the LCD.

Even though I usually use 5v "everything", this particular project does lend itself to 3.3v and so I'll keep these boards and just use them up.

Thanks for your help.

regards
Grant