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Before, HardwareSerial1+.cpp were a copy of HardwareSerial1.cpp with all
0's replaced by the corresponding number. This would mean that e.g.
the Serial1 object would use the UBRRL register instead of UBRR1L when
it was defined, or the USART_RX_vect instead of USART1_RX_vect.
In practice, this would neve actually cause problems, since:
- No avr chip currently has both the non-numbered registers as well as
numbered registers.
- HardwareSerial.h would only define HAVE_HWSERIALx when the
corresponding numbered register is defined (except for
HAVE_HWSERIAL0, which is also defined when the unnumbered registers
are present).
Furthermore, before both the UARTx_xx_vect and USART_x_xx_vect was used.
Looking at the include files, only UART1_xx_vect is actually used (by
iom161.h), the others use USARTx_xx_vect. For this reason,
HardwareSerial1.cpp keeps the preprocessor conditional to select either
UART or USART and the other files use USART unconditionally.
While we're here, also fix the compiler error message when no valid ISR
name was found (it previously said "for the first UART" in all cases).
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See #1847
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Moreover, declaring pointers-to-registers as const and using initializer
list in class constructor allows the compiler to further improve inlining
performance.
This change recovers about 50 bytes of program space on single-UART devices.
See #1711
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By putting the ISRs and HardwareSerial instance for each instance in a
separate compilation unit, the compile will only consider them for
linking when the instance is actually used. The ISR is always referenced
by the compiler runtime and the Serialx_available() function is always
referenced by SerialEventRun(), but both references are weak and thus do
not cause the compilation to be included in the link by themselves.
The effect of this is that when multiple HardwareSerial ports are
available, but not all are used, buffers are only allocated and ISRs are
only included for the serial ports that are used. On the mega, this
lowers memory usage from 653 bytes to just 182 when only using the first
serial port.
On boards with just a single port, there is no change, since the code
and memory was already left out when no serial port was used at all.
This fixes #1425 and fixes #1259.
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