Attiny Serial Out

Minimal bit-bang send serial. 115200 baud for 1/8/16 MHz ATtiny clock.

Available as Arduino library "ATtinySerialOut".

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Features

Perfect for debugging purposes.
Provides Serial.print / println functions for easy software porting.
Code size is only 76 bytes@38400 baud or 196 bytes@115200 baud (including first call).
Provides additional fast printHex() and printlnHex() functions.
Default TX pin is PIN_PB2 on an ATtiny85.
Currently support for: ATtiny13(A), ATtiny25, ATtiny45, ATtiny85, ATtiny24, ATtiny44, ATtiny84, ATtiny87, ATtiny167 and ATtiny88.

Serial functions provided (linefeed is \n instead of \r\n):

    void print(const __FlashStringHelper *aStringPtr);
    void print(const char *aStringPtr);
    void print(char aChar);
    void print(uint8_t aByte, uint8_t aBase = 10);
    void print(int16_t, uint8_t aBase = 10);
    void print(uint16_t aInteger, uint8_t aBase = 10);
    void print(uint32_t aLong, uint8_t aBase = 10);
    void print(uint32_t aLong, uint8_t aBase = 10);
    void print(double aFloat, uint8_t aDigits = 2);

    void printHex(uint8_t aByte); // with 0x prefix

    void println(const __FlashStringHelper *aStringPtr);
    void println(char aChar);
    void println(uint8_t aByte, uint8_t aBase = 10);
    void println(int16_t aInteger, uint8_t aBase = 10);
    void println(uint16_t aInteger, uint8_t aBase = 10);
    void println(int32_t aLong, uint8_t aBase = 10);
    void println(uint32_t aLong, uint8_t aBase = 10);
    void println(double aFloat, uint8_t aDigits = 2);

    void println(void);

Example

#include <Arduino.h>

#if defined(__AVR_ATtiny87__) || defined(__AVR_ATtiny167__)
#define TX_PIN PIN_PA1 // (package pin 2 / TXD on Tiny167) - can use one of PIN_PA0 to PIN_PA7 here
#else
#define TX_PIN PIN_PB2 // (package pin 7 on Tiny85) - can use one of PIN_PB0 to PIN_PB4 (+PIN_PB5) here
#endif

void setup(void) {
    initTXPin();
    Serial.println(F("START " __FILE__ " from " __DATE__ "\r\nUsing library version " VERSION_ATTINY_SERIAL_OUT));
    writeString("OSCCAL=");
    writeUnsignedByteHexWithPrefix(OSCCAL);
}
void loop() {
}

Using the new *.hpp files

In order to support compile options more easily, the line #include <ATtinySerialOut.h> must be changed to #include <ATtinySerialOut.hpp> in your main program (aka *.ino file with setup() and loop()).

In all other files you must use #include <ATtinySerialOut.h>, to prevent multiple definitions linker errors:

If you forget to include ATtinySerialOut.hpp, you will see errors like ATtinySerialOutExample.cpp:38: undefined reference to initTXPin()`.

Compile options / macros for this library

To customize the library to different requirements, there are some compile options / macros available. These macros must be defined in your program before the line #include <TinySerialOut.hpp> to take effect. Modify them by enabling / disabling them, or change the values if applicable.

Name	Default value	Description
`TX_PIN`	PIN_PB2 (PIN_PA1 for ATtiny87/167)	The pin to use for transmitting bit bang serial. These pin names are valid for ATTinyCore and may be different in other cores.
`TINY_SERIAL_DO_NOT_USE_115200BAUD`	disabled	To force using other baud rates. The rates are 38400 baud at 1 MHz (which has smaller code size) or 230400 baud at 8/16 MHz.
`TINY_SERIAL_INHERIT_FROM_PRINT`	disabled	If defined, you can use this class as a replacement for standard Serial as a print class e.g. for functions like void `prinInfo(Print *aSerial)`. Increases program size.

OpenWindowAlarm example

This example issues an alarm if the chip sensor detect a falling teperarure and is fully documented here

Troubleshooting

Error `call of overloaded 'println(fstr_t*)' is ambiguous`

Please use the new Digistump core. Since version 1.2.0, the library is no longer compatible with the old cores supplied by digistump.

Error `type 'TinySerialOut' is not a base type for type 'TwoWire' using Print::write;`

Reason: Another class, e.g. ATTinyCore class TwoWire : public Stream uses the Print class or a Print method, but Print is normally redefined by ATtinySerialOut. You must define TINY_SERIAL_INHERIT_FROM_PRINT before including ATtinySerialOut.hpp, to avoid this error.

Revision History

Version 2.3.1

Added operator bool() for "if(!Serial)..."
Untested support of ATtiny13

Version 2.3.0

Support of all ports of ATtiny88 using ATTinyCore numbering scheme.

Version 2.2.1

Usage of ATTinyCore pin numbering also for ATtiny167.

Version 2.2.0

Usage of ATTinyCore pin numbering scheme e.g. PIN_PB2 and therefore removed USE_PORTB_FOR_TX_PIN.

Version 2.1.1

Adjusted macro for MH-ET LIVE Core.

Version 2.1.0

Added compile guard.
Added USE_PORTB_FOR_TX_PIN to allow TX pin on port B for ATtiny87/167.
Improved #if guard for instance naming.

Version 2.0.0 - 09/2021

Renamed ATtinySerialOut.cpp to ATtinySerialOut.hpp => TX pin can be defined in main program.
Added symbol TINY_SERIAL_INHERIT_FROM_PRINT - if defined, you can use this class as a replacement for standard Serial as a print class.

Version 1.2.2 - 03/2021

Cloned ATtinySerialOut.cpp as ATtinySerialOut.hpp for direct include.
Added ATtiny88 support.

Version 1.2.1 - 10/2020

Added ATtinyX4 support.

Version 1.2.0 - 7/2020

Removed workaround #define __FlashStringHelper fstr_t for old Digispark core < 1.6.8 in order to work with core >= 1.7.0.
Added ATtiny167 support.
Moved functions from h to cpp file.

Version 1.1.0 - 5/2020

Removed symbol TINY_SERIAL_INHERIT_FROM_PRINT and replaced by macro #define Print TinySerialOut
Changed int to int16_t and long to int32_t.
Use utoa() and ultoa() for uint16_t and uint32_t.

Version 1.0.5 - 3/2020

Added function writeCRLF()

Version 1.0.4 - 1/2020

Symbol TINY_SERIAL_INHERIT_FROM_PRINT - if defined, you can use this class as a replacement for standard Serial as a print class.
Improved all ...Hex() functions.
Define FlashStringHelper for digispark.
Changed label loop to txloop in write1Start8Data1StopNoParity() for 38400 baud.

Version 1.0.3

OpenWindowAlarm example updated.

Version 1.0.2

printHex() now using capital letters.
Improved OpenWindowAlarm example.

Version 1.0.1

Renamed example to be consistent.

Version 1.0.0

Initial Arduino library version.

Remark

C version of serial code is included for better understanding, but assembler version is used. This is because for the C code the timing depends on compiler optimisation switches. You should get the right timing if you compile the C code it with Arduino standard settings or:

avr-g++ -I"C:\arduino\hardware\arduino\avr\cores\arduino" -I"C:\arduino\hardware\arduino\avr\variants\standard" -c -g -w -Os -ffunction-sections -fdata-sections -mmcu=attiny85 -DF_CPU=1000000UL -MMD -o "TinySerialOut.o" "TinySerialOut.cpp"

Badges

Extracted from project README