"Converting" a ATMEGA328P with Uno bootloader to 8mhz

Other Hardware 3rd Party Boards
1

Hi everyone,

I have a couple of ATMEGA328P-PU chips with the Uno bootloader happily running at 16Mhz (with an external crystal/clock). My goal is to "convert" them to 8Mhz, using the internal clock. I already figured out I need to upload a new bootloader and change the fuse settings. I tried to accomplish this using an Arduino Uno as ISP, see http://arduino.cc/en/Tutorial/ArduinoISP. On this page I found this wiring:

But I'm not successful when trying to burn the bootloader (in the Extra menu of the Arduino IDE), I get the error "avrdude: stk500_getsync(): not in sync: resp=0x00".

Can anybody confirm this is the right approach to accomplish what I'm trying to do?

Thanks!
Jan

2

Did you burn the bootloader and fuse settings with the 16MHz crystal still connected first, before removing the crystal?

3

Telecommando:
Your target 328 device needs a clock source or the UNO can't program it.

Thanks for the tip, how can I add the clock source? Adding a crystal? If so should it be a 16Mhz or 8Mhz?

hiduino:
Did you burn the bootloader and fuse settings with the 16MHz crystal still connected first, before removing the crystal?

Thanks for the reply! tried without a crystal connected. (I bought the chips with a bootloader on them, so I didn't burn the 16Mhz bootloader)

4

My goal is to "convert" them to 8Mhz, using the internal clock

The internal frequency is not exactly 8MHz. You must calibrate it with the OSCCAL.

5

Telecommando:
Yes, you will either need to add a crystal (8 or 16 MHZ, doesn't really matter, just wire as shown on the page you linked)

Or

You can also use an ISP sketch that provides a clock source like this one:
GitHub - adafruit/ArduinoISP: A fork of the ArduinoISP that has 8mhz output clock

Which provides an 8 MHz clock signal on the UNO's Digital 9 pin, which then needs to be jumpered to pin 9 of the target 328.

Thanks for the great advice! It's now working!

6

Hi... May you explain how you did it!?... Im having the same problem, but Im still learning and I cant figure out how to do it properly.

thanks!!

7

http://forum.arduino.cc/index.php?topic=124879.0

The bug mentioned there is no longer present in the latest version of the IDE.