Previously, the constants to use for the bit positions of the various
UARTs were passed to the HardwareSerial constructor. However, this
meant that whenever these values were used, the had to be indirectly
loaded, resulting in extra code overhead. Additionally, since there is
no instruction to shift a value by a variable amount, the 1 << x
expressions (inside _BV and sbi() / cbi()) would be compiled as a loop
instead of being evaluated at compiletime.
Now, the HardwareSerial class always uses the constants for the bit
positions of UART 0 (and some code is present to make sure these
constants exist, even for targets that only have a single unnumbered
UART or start at UART1).
This was already done for the TXC0 constant, for some reason. For the
actual register addresses, this approach does not work, since these are
of course different between the different UARTs on a single chip.
Of course, always using the UART 0 constants is only correct when the
constants are actually identical for the different UARTs. It has been
verified that this is currently the case for all targets supported by
avr-gcc 4.7.2, and the code contains compile-time checks to verify this
for the current target, in case a new target is added for which this
does not hold. This verification was done using:
for i in TXC RXEN TXEN RXCIE UDRIE U2X UPE; do echo $i; grep --no-filename -r "#define $i[0-9]\? " /usr/lib/avr/include/avr/io* | sed "s/#define $i[0-9]\?\s*\(\S\)\+\s*\(\/\*.*\*\/\)\?$/\1/" | sort | uniq ; done
This command shows that the above constants are identical for all uarts
on all platforms, except for TXC, which is sometimes 6 and sometimes 0.
Further investigation shows that it is always 6, except in io90scr100.h,
but that file defines TXC0 with value 6 for the UART and uses TXC with
value 0 for some USB-related register.
This commit reduces program size on the uno by around 120 bytes.
This simplifies the baud rate calculation, removing the need for a goto
and shortening the code a bit. Other than that, this code should not use
any different settings than before.
Code was suggested by Rob Tillaart on github.
Closes: #1262
There are two begin methods, one which accepts just a baud rate and
uses the default bit settings and one which accepts both a baudrate and
a bit config. Previously, both of these contained a complete
implementation, but now the former just calls the latter, explicitely
passing the default 8N1 configuration.
Technically, this causes a small change: Before the UCSRC register was
untouched when calling begin(baud), now it is explicitely initialized
with 8N1. However, since this is the default configuration for at least
the Uno and the Mega (didn't check any others), probably for all avrs,
this shouldn't effectively change anything. Given that the Arduino
documentation also documents this as the default when none is passed,
explicitly setting it is probably a good idea in any case.
These functions do not modify the IPAddress object, but were not marked
as const. This meant that you could not do:
void set_ip(const IPAddress& ip) {
uint32_t copy = ip;
}
Since calling operator uint32_t() on ip would discard the constness of
the reference.
"runtime.hardware.path" now contains the path to the hardware folder
of the currently selected board and "runtime.platform.path" the path
to the specific platform.
This should fix#1176 and #1761.
On later versions of avr-libc, prog_char is deprecated. In 0acebeeff48
the one occurence of prog_char was replaced by "char PROGMEM", which is
not entirely correct (PROGMEM is supposed to be an attribute on a
variable, not on a type, even though this is how things work in older
libc versions). However, in 1130fede3a2 a few new occurences of
prog_char are introduced, which break compilation on newer libc versions
again.
This commit changes all these pointer types to use the PGM_P macro from
<avr/pgmspace.h>. This macro is just "const char *" in newer libc
versions and "const prog_char *" in older versions, so it should always
work.
References #795
The new function just calls Print::write(const uint8_t *, size_t), but
this allows writing out a buffer of chars (without having to learn about
casts).
Matthijs Kooijman
Cristian Maglie
Federico Fissore
Kristian Lauszus
ntruchsess