Ethernet shiled+ Duemilanove at 4MHz

Hello everyone!!

I have a Duemilanove board with ATMEGA328. I have compiled a bootloader and changed clock frequency to 4MHz. When I connected an Ethernet shield to the Duemilanove with 16MHz clock everything works fine. But when I connected an Ethernet shield with new frequency clock, 4MHz, doesn´t work. Ethernet shiled works only with Duemilanove at 16MHz clock?

Thanks in advance.

Regards.

I have compiled a bootloader and changed clock frequency to 4MHz.

Why? What are you trying to accomplish by running the Arduino slower?

Dear PaulS,

I running Arduino slower because I need to use 3.3V level to communicate with SD cards without translator levels and others devices that runs at same voltage level.

Anyone can help me?

Thanks.

Take a look at the Ethernet shield schematic - http://arduino.cc/en/uploads/Main/arduino-ethernet-shield-05-schematic.pdf There are plenty of +5Vs on that schematic. I don't think you can run that shield at 3.3V.

The Ethernet shield has a SD card slot, and manages the voltage levels. There is 3.3V power available on the Arduino when running at 16MHz/+5V. Most 3.3V sensors are 5V tolerant.

Is there some reason to run another SD card reader? What sensors do you have that are not 3.3V tolerant? Can't you power them from the 3.3V pin or through a voltage divider connected to a digital pin?

Dear PaulS,

First of all thanks for your interest and fast reply. I have designed a homebrew shield with various voltage regulators. One of them powers Ethernet shield, and rest: A/D (AN7706, 3.3 V), voltage inverters and RTD circuits. So A/D and SD card works at 3.3V, and I have a LDO too with the same voltage, I decided to power all at 3.3V.

Do you know if Ethernet shield can work with Duemilanove at 4MHz?

Thanks in advance.

Regards.