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Topic: software serial2 (Read 4282 times) previous topic - next topic

ladyada

i need to use software serial to interface with the xport, but i couldnt get consistant results, even at 9600 so i poked at it a little and made a version that uses a pinchange interrupt (for diecimila or NG with chip upgrade only!). now it buffers the input characters to avoid the dreaded 'lost bits' errors i got.
it seems to work great! i will clean it up and make it more 'objecty' and maybe turn it into a library, but if someone wants to play with it...

/*
* Software UART
*
*/

int ledPin = 13;                // LED connected to digital pin 13

/***************************************************************************************/

#include <avr/pgmspace.h>

#define altPrint(x) alt_ROMputstring(PSTR(x), 0)
#define altPrintln(x) alt_ROMputstring(PSTR(x), 1)

int rxpin, txpin, altserialdelay = 0;
#define MAX_ALTRX_BUFF 8
char altRXD[MAX_ALTRX_BUFF];
int altrxsize = 0;

SIGNAL(SIG_PIN_CHANGE0)
{
 if ((rxpin >=8) && (rxpin <= 13)) {
   altRecv();
 }
}
SIGNAL(SIG_PIN_CHANGE2)
{
 if (rxpin <8) {
   altRecv();
 }
}

void altDelay(int delay) {
 while (delay != 0) {
    delay--;
 }
}

void altRecv(void) {
 char i, d = 0;
 if (digitalRead(rxpin))
   return;       // not ready!
 altDelay(altserialdelay-5); // one half bit
 for (i=0; i<8; i++) {
   PORTB |= _BV(5);
   altDelay(altserialdelay*2); // one bit
   PORTB &= ~_BV(5);
   if (digitalRead(rxpin))
     d |= (1 << i);
 }
 altRXD[altrxsize] = d; // save data
 altrxsize++;  // got a byte
 altDelay(altserialdelay*2);
}

void altSerialSetup(int baudrate, char tx, char rx) {
 txpin = tx;
 pinMode(txpin, OUTPUT);
 digitalWrite(txpin, HIGH);
 rxpin = rx;
 pinMode(rxpin, INPUT);
 digitalWrite(rxpin, HIGH);  // pullup!
 if (baudrate == 19200) {
    altserialdelay = 62; // these are determined experimentally
 } else if (baudrate == 9600) {
    altserialdelay = 128;  // these are determined experimentally
 }    
 if (rxpin < 8) {
   // a PIND pin, PCINT16-23
   PCMSK2 |= _BV(rxpin);
   PCICR |= _BV(2);
 } else if (rxpin <= 13) {
   // a PINB pin, PCINT0-5
   PCICR |= _BV(0);    
   PCMSK0 |= _BV(rxpin-8);
 }
}


void altPutchar(char d) {
 int i;
 cli();  // turn off interrupts, make it nice & kleen
 digitalWrite(txpin, LOW);       //start bit
 altDelay(altserialdelay*2);
 for (i=0; i< 8; i++) {
   if (d & 0x1) {
      digitalWrite(txpin, HIGH);
   } else {
      digitalWrite(txpin, LOW);
   }
   altDelay(altserialdelay*2);
   d >>= 1;
 }
 digitalWrite(txpin, HIGH);     // one stop bit
 sei();   // turn on interrupts
 altDelay(altserialdelay*2);  
}

void alt_ROMputstring(const char *str, uint8_t nl) {
 uint8_t i;

 for (i=0; pgm_read_byte(&str); i++) {
   altPutchar(pgm_read_byte(&str));
 }
 if (nl) {
   altPutchar('\n'); altPutchar('\r');
 }
}
void altPrintNumber(uint16_t n) {
     uint8_t cnt=0, flag=0;
     
     while (n >= 10000UL) { flag = 1; cnt++; n -= 10000UL; }
     if (flag) altPutchar('0'+cnt);
     cnt = 0;
     while (n >= 1000UL) { flag = 1; cnt++; n -= 1000UL; }
     if (flag) altPutchar('0'+cnt);
     cnt = 0;
     while (n >= 100UL) { flag = 1; cnt++; n -= 100UL; }
     if (flag) altPutchar('0'+cnt);
     cnt = 0;
     while (n >= 10UL) { flag = 1; cnt++; n -= 10UL; }
     if (flag) altPutchar('0'+cnt);
     cnt = 0;
     altPutchar('0'+n);
     return;
}

int altAvailable(void) {
 
 
}

/***************************************************************************************/



void setup()                    // run once, when the sketch starts
{
 pinMode(ledPin, OUTPUT);      // sets the digital pin as output
 altSerialSetup(9600, 2, 3);
 Serial.begin(9600);
}

int counter=0;
void loop()                     // run over and over again
{
 digitalWrite(ledPin, LOW);    // sets the LED off

 if (altrxsize) {
     Serial.print(altRXD[0]);
     altrxsize--;
 }
 if (Serial.available()) {
     altPutchar(Serial.read());
 }

}


mellis

Awesome.

The current SoftwareSerial library kind of sucks, so it would be great to have this as a replacement.  Let us know when you do and I can include it in the distribution.

ladyada

ok i fixed it

http://www.ladyada.net/make/eshield/AFSoftSerial.zip

supports RX and TX, up to 57600 tested. due to the delay inherent in digitalRead() its probably not possible to go any faster.
should probably be poked at by others. currently only for Diecimila (16mhz atmega168)

#include <AFSoftSerial.h>

AFSoftSerial mySerial =  AFSoftSerial(3, 2);

void setup()  {
 pinMode(13, OUTPUT);
 Serial.begin(9600);
 // set the data rate for the SoftwareSerial port
 mySerial.begin(9600);
 mySerial.println("Hello, world...");
}

void loop()                     // run over and over again
{
 if (mySerial.available()) {
     Serial.print((char)mySerial.read());
 }
 if (Serial.available()) {
     mySerial.print((char)Serial.read());
 }
}

John_Ryan

#3
Feb 06, 2008, 04:53 am Last Edit: Feb 06, 2008, 04:55 am by John_Ryan Reason: 1
Quote
ok i fixed it

http://www.ladyada.net/make/eshield/AFSoftSerial.zip

supports RX and TX, up to 57600 tested. due to the delay inherent in digitalRead() its probably not possible to go any faster.
should probably be poked at by others. currently only for Diecimila (16mhz atmega168)

#include <AFSoftSerial.h>

AFSoftSerial mySerial =  AFSoftSerial(3, 2);

void setup()  {
 pinMode(13, OUTPUT);
 Serial.begin(9600);
 // set the data rate for the SoftwareSerial port
 mySerial.begin(9600);
 mySerial.println("Hello, world...");
}

void loop()                     // run over and over again
{
 if (mySerial.available()) {
     Serial.print((char)mySerial.read());
 }
 if (Serial.available()) {
     mySerial.print((char)Serial.read());
 }
}


What a genius, you rock! That fixes a huge problem, that would enable a few serial devices to be connected to one board, how did you do it?

Will it work with BT's, Lilypads and NG's?

ladyada

Quote

What a genius, you rock! That fixes a huge problem, that would enable a few serial devices to be connected to one board, how did you do it?


actually you can only have one software serial device at a time (right now) because of the pinchange interrupt. i could adapt it for more but its a real hassle and, well, i figure this is good enough for now.

Quote

Will it work with BT's, Lilypads and NG's?


er, no..."currently only for Diecimila (16mhz atmega168)"  ;)

mem

Thanks for that, it will be a huge help.

One question, with interrupts turned off when sending a char, does that mean that receive bits will be lost if they are presented at the same time as a character is being sent?

John_Ryan

Quote
[

er, no..."currently only for Diecimila (16mhz atmega168)"  ;)


er, pity

ladyada

Quote
Thanks for that, it will be a huge help.

One question, with interrupts turned off when sending a char, does that mean that receive bits will be lost if they are presented at the same time as a character is being sent?


yes
but the old software serial couldnt do that either so its not really a big deal

ladyada

Quote
Quote
[

er, no..."currently only for Diecimila (16mhz atmega168)"  ;)


er, pity



send me a lilypad an an NG with an 8mhz xtal and ill make it work with 'em!

John_Ryan

Quote
Quote
Quote
[

er, no..."currently only for Diecimila (16mhz atmega168)"  ;)


er, pity

send me a lilypad an an NG with an 8mhz xtal and ill make it work with 'em!


I needed a solution a while back, but improvised this instead.

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1201476854/5#5

This should work with your 168's aye, if I wanted to make something like a dualCoreDuino  ;D

mem

#10
Feb 06, 2008, 10:58 am Last Edit: Feb 06, 2008, 11:01 am by mem Reason: 1
Quote
Quote
Thanks for that, it will be a huge help.

One question, with interrupts turned off when sending a char, does that mean that receive bits will be lost if they are presented at the same time as a character is being sent?


yes
but the old software serial couldnt do that either so its not really a big deal
No big deal at all (as long as users are aware that data may be missed if received while sending). Many thanks for taking the time and effort to impliment this. It will be very useful to me and I am sure many other people.




Cheater

Quote
er, no..."currently only for Diecimila (16mhz atmega168)"  ;)

Isnt the Lillypad a 168? Not sure about the Bluetooth one.

mem

Quote
Quote
er, no..."currently only for Diecimila (16mhz atmega168)"  ;)

Isnt the Lillypad a 168? Not sure about the Bluetooth one.
I believe the lilypad uses the internal clock so runs at 8mhz.  

kwan6887

Hello ladyada,

     I am working on the RFID reader which operates at baudrate 2400. I have tried to amend your coding in order to support it but I cannot figure out the correct  _bitDelay for baudrate 2400....

Would you please provide me the library that supports baudrate 2400?!

Thanks for your assistant in advance!!!!!

John_Ryan

You don't need to be changing the library, the parameters are set by the application.

SS works "up to" 9600, so the phidgets at 2400 should be fine

Code: [Select]

#include <AFSoftSerial.h>

AFSoftSerial mySerial = AFSoftSerial(3, 2);

void setup() {
 pinMode(13, OUTPUT);
 Serial.begin(9600);
 // set the data rate for the SoftwareSerial port
 mySerial.begin(2400);
 mySerial.println("Hello, world...");
}

void loop()           // run over and over again
{
 if (mySerial.available()) {
   Serial.print((char)mySerial.read());
 }
 if (Serial.available()) {
   mySerial.print((char)Serial.read());
 }
}


You'll need to remove the 'hello world' of course :)

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