Atmega 1284P speed variantion from one chip to another

Other Hardware 3rd Party Boards
1

Hi,

I'm currently working on an Atmega1284P projet. I have design my own board, and i have a very very strange bug.

I'm stil working on my board, i plan to add a enc28j60 chip, a full POE (802.af) system, a ssd1306 screen and lot of sensor. But now i have just a led on lthe pin 31, the oscilator and the ISP header.

I have 5 atmega1284P :

One from a vendor on ebay, this one work without issue

Four from another vendor on ebay, they works to, but ten time slower than the first one ... WTF

I am using a USBasp to flash the chip.

Some has an idea ?

Thank in advance for your help

agemio

2

Did you burn the fuses in all of them the same, for external 16 MHz crystal for example?

3

Betcha it's 8 times slower - or 16 - not 10.

Either way, the low fuse is set wrong - the divide by 8 bit is programmed, and you may also have it using internal 8mhz clock instead of a crystal (if you're using a crystal). The chip defaults to 1mhz operation (8mhz internal divided by 8 ), so it will run at the lowest supported voltage. You should be able to correct this by selecting the board and clock speed/source you want from the boards menu, and doing 'burn bootloader' (even if not using the bootloader, this sets the fuses to use the clock source you want.

4

I have add the following line to my board.txt file and burn the bootloader :

ATmega1284p-16.bootloader.low_fuses=0xff
ATmega1284p-16.bootloader.high_fuses=0xdc
ATmega1284p-16.bootloader.extended_fuses=0xfd
ATmega1284p-16.bootloader.tool=avrdude
ATmega1284p-16.bootloader.unlock_bits=0x3F
ATmega1284p-16.bootloader.lock_bits=0x0F
ATmega1284p-16.bootloader.file=1284/ATmegaBOOT_1284P.hex

It's wordking on every chip now.

Thank's a lot