In upgrading from 3.7 to 3.8 I found that printf was broken. I was using a series of "%c%c" format to generate a Modbus packet to a sensor. Printf in 3.7 did the right thing with a '\0' character (sent a null character) but in 3.8, it ignores it and does not output anything. I was able to work around it by using a series of "fputc()" calls instead. I did submit a bug report to Freescale but I have not heard back.