twiboot timeout issue

[MS71]

Hi,
i ported twiboot to my Tiny84 target.
So far, it is working. I am able to download the code and start a small demo application via the I2C command.

Unfortunately, it is not starting without any I2C communication (timeout).
Any hint?

For debugging, i added some fast LED toggling just before jump_to_app();
The problem, is, that my app code is just not working, when it is started by timeout.

Additional, i think there is a concept error with the appvect_save variable.
I think, the appvect_save & rstvect_save are initialized with the wrong value in main.
When I check/compare without writing it, then i get a mismatch with the original code.

I think, it should be:
rstvect_save[0] = buf[APPVECT_PAGE_OFFSET];
rstvect_save[1] = buf[APPVECT_PAGE_OFFSET + 1];
appvect_save[0] = ?;
appvect_save[1] = ?;

I added a simple CRC16 checksum query. This is very useful doing a quick code compare without read the entire flash to the master.

Later, i like to add support for the AT Tiny841 too. This device has a different I2C slave implementation.

Shall i provide a pull request for this?

Maik

[orempel]

Moin,
without seeing your code changes I would guess that the HW timer is not running correctly and thus never setting "cmd = CMD_BOOT_APPLICATION" in TIMER0_OVF_vect. Might be an overflow in the TIMER_MSEC2TICKS / TIMER_MSEC2IRQCNT calculation if you have changed the default values for those.

There is no concept error in the virtual boot handling:
Verify is only possible after flashing, since the RESET vector and the "app" vector (EE_RDY by default) are patched while writing:

• the "app" vector is patched to store the user application entry address (taken from the RESET vector of the hex file you are flashing)
• the RESET vector is patched to store the twiboot entry address (eg. 0x1C00)

This is required to start twiboot before the user application without having a bootloader section. It implies that the "app" vector must never be used by the application since it is used by twiboot.