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Modifying SoftwareSerial timing to work with new digitalRead() and digitalWrite() functions.

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This commit is contained in:
David A. Mellis 2007-04-20 23:18:25 +00:00
parent d277488310
commit 81b0054893
2 changed files with 14 additions and 11 deletions
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20
targets/libraries/SoftwareSerial/SoftwareSerial.cpp
View File

@ -46,14 +46,16 @@ SoftwareSerial::SoftwareSerial(uint8_t receivePin, uint8_t transmitPin)
void SoftwareSerial::begin(long speed)
{
_baudRate = speed;
_bitPeriod = 1000000 / _baudRate;
digitalWrite(_transmitPin, HIGH);
delayMicroseconds( _bitPeriod); // if we were low this establishes the end
}
int SoftwareSerial::read()
{
int val = 0;
int width = 1000000 / _baudRate;
int fudge = -8;
//int fudge = -16;
int bitDelay = _bitPeriod - clockCyclesToMicroseconds(50);
// one byte of serial data (LSB first)
// ...--\ /--\/--\/--\/--\/--\/--\/--\/--\/--...
@ -66,18 +68,18 @@ int SoftwareSerial::read()
if (digitalRead(_receivePin) == LOW) {
// frame start indicated by a falling edge and low start bit
// jump to the middle of the low start bit
delayMicroseconds(width / 2);
delayMicroseconds(bitDelay / 2 - clockCyclesToMicroseconds(50));
// offset of the bit in the byte: from 0 (LSB) to 7 (MSB)
for (int offset = 0; offset < 8; offset++) {
// jump to middle of next bit
delayMicroseconds(width + fudge);
delayMicroseconds(bitDelay);
// read bit
val |= digitalRead(_receivePin) << offset;
}
delayMicroseconds(width + fudge);
delayMicroseconds(_bitPeriod);
return val;
}
@ -90,7 +92,7 @@ void SoftwareSerial::print(uint8_t b)
if (_baudRate == 0)
return;
int bitDelay = 1000000 / _baudRate - 15;
int bitDelay = _bitPeriod - clockCyclesToMicroseconds(50); // a digitalWrite is about 50 cycles
byte mask;
digitalWrite(_transmitPin, LOW);
@ -110,7 +112,7 @@ void SoftwareSerial::print(uint8_t b)
delayMicroseconds(bitDelay);
}
void SoftwareSerial::print(char *s)
void SoftwareSerial::print(const char *s)
{
while (*s)
print(*s++);
@ -167,7 +169,7 @@ void SoftwareSerial::println(char c)
println();
}
void SoftwareSerial::println(char c[])
void SoftwareSerial::println(const char c[])
{
print(c);
println();

5
targets/libraries/SoftwareSerial/SoftwareSerial.h
View File

@ -28,13 +28,14 @@ class SoftwareSerial
uint8_t _receivePin;
uint8_t _transmitPin;
long _baudRate;
int _bitPeriod;
void printNumber(unsigned long, uint8_t);
public:
SoftwareSerial(uint8_t, uint8_t);
void begin(long);
int read();
void print(char);
void print(char[]);
void print(const char[]);
void print(uint8_t);
void print(int);
void print(unsigned int);
@ -43,7 +44,7 @@ class SoftwareSerial
void print(long, int);
void println(void);
void println(char);
void println(char[]);
void println(const char[]);
void println(uint8_t);
void println(int);
void println(long);