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Commit Graph

24 Commits

Author SHA1 Message Date
Matthijs Kooijman
87f89f6100 Optimize SoftwareSerial::recv
Similar to SoftwareSerial::write, this rewrites the loop to only touch
the MSB and then shift those bits up, allowing the compiler to generate
more efficient code. Unlike the write function however, it is not needed
to put all instance variables used into local variables, for some reason
the compiler already does this (and doing it manually even makes the
code bigger).

On the Arduino Uno using gcc 4.3 this saves 26 bytes. Using gcc 4.8 this
saves 30 bytes.

Note that this removes the else clause in the code, making the C code
unbalanced, which looks like it breaks timing balance. However, looking
at the code generated by the compiler, it turns out that the old code
was actually unbalanced, while the new code is properly balanced.
2015-01-26 17:03:25 +01:00
Matthijs Kooijman
764f24266e Further optimize SoftwareSerial::write
This change restructures the loop, to help the compiler generate shorter
code (because now only the LSB of the data byte is checked and
subsequent bytes are shifted down one by one, it can use th "skip if bit
set" instruction).

Furthermore, it puts most attributes in local variables, which causes
the compiler to put them into registers. This makes the timing-critical
part of the code smaller, making it easier to provide accurate timings.

On an Arduino uno using gcc 4.3, this saves 58 bytes. On gcc 4.8, this
saves 14 bytes.
2015-01-26 17:03:25 +01:00
Matthijs Kooijman
80ea38b1dc Mark SoftwareSerial::tx_pin_write as "always_inline"
Somehow gcc 4.8 doesn't inline this function, even though it is always
called with constant arguments and can be reduced to just a few
instructions when inlined. Adding the always_inline attribute makes gcc
inline it, saving 46 bytes on the Arduino uno.

gcc 4.3 already inlined this function, so there are no space
savings there.
2015-01-26 17:03:25 +01:00
Matthijs Kooijman
416198a03b Simplify SoftwareSerial::write
Before, there was nearly identical code for the inverted and regular
cases. However, simply inverting the byte in the inverted case allows
using the regular code twice, reducing the generated code size by 100
bytes (on an Arduino Uno and gcc 4.3, on gcc 4.8 the reduction is 50
bytes).
2015-01-26 17:03:25 +01:00
Matthijs Kooijman
6685aa999c Use stopListening() in SoftwareSerial::end()
stopListening also disabled the interrupt, if needed, so calling that
function makes more sense. Since stopListening only disables the
interrupt when the current SoftwareSerial is the active object, and that
can only be the case when _rx_delay_stopbit is non-zero, there is no
need to separately check _rx_delay_stopbit anymore.
2015-01-26 17:03:25 +01:00
Matthijs Kooijman
f3aa5f23c4 Fix race condition in SoftwareSerial::overflow()
If an interrupt causing overflow would occur between reading
_buffer_overflow and clearing it, this overflow condition would be
immediately cleared and never be returned by overflow().

By only clearing the overflow flag if an overflow actually occurred,
this problem goes away (worst case overflow() returns false even though
an overflow _just_ occurred, but then the next call to overflow() will
return true).
2015-01-26 17:03:25 +01:00
Matthijs Kooijman
b1de3e6621 Toggle SoftwareSerial interrupts when starting / stopping to listen
This prevents interrupts from triggering when the SoftwareSerial
instance is not even listening.

Additionally, this removes the need to disable interrupts in
SoftwareSerial::listen, since no interrupts are active while it touches
the variables.
2015-01-26 17:03:25 +01:00
Matthijs Kooijman
934393398b Add SoftwareSerial::stopListening()
This allows one to explicitly stop a SoftwareSerial instance from
listening, without having to make another one listening.
2015-01-26 17:03:25 +01:00
Matthijs Kooijman
db1a4ad139 Add SoftwareSerial::setRxIntMsk()
This moves the interrupt mask enabling / disabling code into a separate
method, so we can call it from multiple spots next.
2015-01-26 17:03:25 +01:00
Matthijs Kooijman
1704e7e820 Let SoftwareSerial::end also check against _rx_delay_stopbit
The current check is still always false when the old check was, but
additionally it will not disable the interrupts when they were never
enabled (which shouldn't matter much, but this is more consistent).
2015-01-26 17:03:24 +01:00
Matthijs Kooijman
b1c7a3d05f Let SoftwareSerial::listen() fail on invalid rx baud rates
In this case, SoftwareSerial::begin will not have enabled the
interrupts, so better not allow the SoftwareSerial instance to enter the
listening state either.
2015-01-26 17:03:24 +01:00
Matthijs Kooijman
937cc51c69 Clear SoftwareSerial rx delay if no interrupt register is found
Before enabling interupts, begin would see if the given receive pin
actually has an associated PCINT register. If not, the interrupts would
not be enabled.

Now, the same check is done, but when no register is available, the rx
parameters are not loaded at all (which in turn prevents the interrupt
from being enabled). This allows all code to use the same "is rx
enabled" (which will be added next).
2015-01-26 17:03:24 +01:00
Fede85
dd77375fe9 missing paragraph field in library.properties 2014-07-18 20:08:01 +02:00
Fede85
b02e85ceb2 modified sentences in library.properties files 2014-07-18 19:41:34 +02:00
Cristian Maglie
5d92c1ba8e Merge remote-tracking branch 'arduino/master' into ide-1.5.x
Conflicts:
	build/shared/examples/01.Basics/Blink/Blink.ino
	build/shared/examples/09.USB/Keyboard/KeyboardReprogram/KeyboardReprogram.ino
	build/shared/examples/10.StarterKit/p02_SpaceshipInterface/p02_SpaceshipInterface.ino
	hardware/arduino/cores/arduino/HardwareSerial.cpp
2014-05-23 21:04:47 +02:00
Cristian Maglie
7f17170678 Revert "SoftwareSerial library to the new format"
This reverts commit 38c3bbbd3c.
2013-11-15 12:54:59 +01:00
Fede85
38c3bbbd3c SoftwareSerial library to the new format 2013-07-03 23:18:21 +02:00
Cristian Maglie
3394f61276 Merged 1.0.5 2013-05-29 18:30:36 +02:00
Cristian Maglie
66ee23b885 Merged 1.0.3 2012-12-10 15:55:05 +01:00
Federico Fissore
d458ef7806 fixed permissions on a lot of text files. see #1116 2012-12-10 10:42:49 +01:00
Cristian Maglie
46aeeb4b29 Merged upstream Arduino master branch 2012-06-26 00:51:35 +02:00
Cristian Maglie
33083d84b3 Merge of arduino-1.0.1. Work in progress... 2012-05-23 09:22:52 +02:00
Cristian Maglie
b276a75d13 Pre-merge upstream Arduino 2012-05-22 11:23:47 +02:00
Cristian Maglie
57b8713cab Moved libraries folder inside platform folder. Now libraries and examples are searched per board/platform 2012-01-04 15:14:51 +01:00