read_frame was misuing the packet length in the following ways:
- returning non-zero even if buf_len is too short for the packet
- truncating the length to buf_len if len is too long then using the
truncated (i.e. wrong) length to index into the buffer
- memcpying too many bytes (used buf_len instead of real length)
This commit fixes all of this and adds some code to report
on packet length errors (to match with cc2538 driver).
- moved variable declaration to top of function in accordance with the
Contiki style guide
- made function flatter, reduced nesting to improve readability
Enabling this option seems to greatly improve transciever performance with
Contikimac. This seems to happen because Contikimac CCAs are much less likely
to detect false positives (thus screwing up the CCA sequence).
* Only enable TX by default.
* Add some magic for RX handling. When an input handler is registered:
* Automatically enable RX-related and interrupts
* Automatically lock the SERIAL PD on under all power modes
* Automatically enable the UART clock under sleep and deep sleep
* Automatically undo all of the above when the input handler becomes NULL
* As a result, modules / examples that need UART RX no longer need to clock the UART and manipulate the SERIAL PD. They simply have to specify an input handler
* Don't automatically power on the UART whenever the CM3 is active
* Before accessing the UART, make sure it is powered and clocked
* Avoid falling edge glitches
* Fix garbage characters / Explicitly wait for UART TX to complete
Instead of using a separate data structure to request that a PD remain powered during deep sleep,
we do the same within the main LPM data structure through an additional field.
This allows us to maintain only one linked list of LPM modules and overall improves code clarity
