YO3BN - Atmega1284-PU Quick Info

Atmega1284-PU Quick Info

Posted at - 17th December 2017

This is not a tutorial about MCUs, but it's just a bunch of notes, tips and quick references easy to remember.

Atmega1284-PU vs Atmega1284P-PU

They are almost same MCU, the only notable difference between them is their signature and PicoPower feature for Atmega1284P-PU.

Signature for Atmega1284-PU: 0x1e 0x97 0x06
Signature for Atmega1284P-PU: 0x1e 0x97 0x05

Using avrdude version 5.11.1 will fail to flash Atmega1284-PU due signature mismatch:

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$ sudo avrdude -c usbtiny -p m1284p -U flash:w:-U flash:w:a.hex:i

avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.01s

avrdude: Device signature = 0x1e9706
avrdude: Expected signature for ATMEGA1284P is 1E 97 05
Double check chip, or use -F to override this check.

avrdude done. Thank you.

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If this is the case, you must edit /etc/avrdude.conf by changing device signature from 0x1e 0x97 0x05 to 0x1e 0x97 0x06 in ATmega1284P section or a more elegant method to copy the entire ATmega1284P section, changing its title, id, desc, signature accordingly.

Now the new added MCU can be verified by issuing the following command:
$ avrdude -c usbtiny -p list

...
m1284 = ATMEGA1284 [/etc/avrdude.conf:4953]
m1284p = ATMEGA1284P [/etc/avrdude.conf:4760]
...

Atmega1284-PU JTAG Enabled by Default

The JTAG is enabled by default on this device, thus PC5:PC2 pins are pulled-up to high state. To disable JTAG the high fuse byte should be modified from HFUSE = 0x99 to HFUSE = 0xD9 like follows:

$ sudo avrdude -c usbtiny -p m1284 -U hfuse:r:-:h
$ sudo avrdude -c usbtiny -p m1284 -U hfuse:w:0xD9:m

External Crystal Clock Full Swing

By default clock division by 8 and internal RC 8MHz are used in low fuse, its default value is 0x62.

Enabling external crystal oscillator with full swing:
$ sudo avrdude -c usbtiny -p m1284 -U lfuse:w:0x67:m

Disabling clock division:
$ sudo avrdude -c usbtiny -p m1284 -U lfuse:w:0xE7:m

73 de YO3BN