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Topic: SPI interface with other board_AVR_ESK1100 or among Arduino itself (Read 12163 times) previous topic - next topic

Nick Gammon


This code works fine with making SPDR = 0x00; at ISR but I have observed on Oscilloscope that sometime few data goes back to MISO, Slave is not able to clear SPDR perfectly, what could be the reason.
...
Just keeping bandwidth of site in mind I am attaching one oscilloscope photo for your reference.


I can reproduce that. I am guessing that the Timer interrupt (used by millis() and delay() ) is slowing it down enough that it cannot respond quickly (this would happen every few milliseconds, because if the timer interrupt happens to fire when the SPI interrupt needs to fire, the SPI interrupt won't change SPDR fast enough).

By adding this line to setup the problem goes away:

Code: [Select]

  // disable timer interrupts
  TIMSK0 = 0;


Modified sketch:

Code: [Select]

//Slave receiving data
#include <SPI.h>

void setup (void)
{
  Serial.begin(115200);
  // have to send on master in, *slave out*
  pinMode(MISO, OUTPUT);
  SPI.setBitOrder(MSBFIRST);
  SPI.setDataMode (SPI_MODE2);
  SPI.setClockDivider(SPI_CLOCK_DIV64) ;

  // turn on SPI in slave mode
  SPCR |= _BV(SPE);

  // turn on interrupts
  SPCR |= _BV(SPIE);

  // disable timer interrupts
  TIMSK0 = 0;
}  // end of setup


// SPI interrupt routine
ISR (SPI_STC_vect)
{
  byte c = SPDR;  // what we received from the master
  SPDR = 0;    // what to return to the master
}  // end of ISR SPI_STC_vect


void loop (void)
{

}  // end of loop


This is why you cannot use delay inside the ISR (as you had, commented out). In any case, delay() doesn't work inside an ISR.

The ISR has to be fast, because if you don't change SPDR fast enough, the incorrect data will be sent on the next transfer.

Of course, if you turn off timer interrupts you won't know how much time has elapsed.

What you could do is have an interrupt on the SS (slave select) line. When that goes low, turn off timer interrupts, wait for the incoming data, and when SS goes high again, turn timer interrupts back on.
Please post technical questions on the forum, not by personal message. Thanks!

More info:
http://www.gammon.com.au/electronics

Nick Gammon


This code works fine with making SPDR = 0x00; at ISR but I have observed on Oscilloscope that sometime few data goes back to MISO, Slave is not able to clear SPDR perfectly, what could be the reason.


I'm not convinced you read and understood my page here:

http://www.gammon.com.au/spi


In that I mention this exact problem. To get a response you need to allow time for the slave to do whatever it needs to do, and set up a response (ie. set SPDR). See this diagram from that page:



In the code on that page I built in a delay on the master end, to slow down communications long enough to give the slave time to respond. It's all on the page. Please read it again, and again.


Quote
... what could be the reason.


You need to read my page and understand it.
Please post technical questions on the forum, not by personal message. Thanks!

More info:
http://www.gammon.com.au/electronics

Graynomad

Is channel 1 on the scope trace really set to 50mV/div? If so you are in deep trouble.

At the other extreme the top trace seems to pulse well over 7v. Is that right?

______
Rob
Rob Gray aka the GRAYnomad www.robgray.com

Nick Gammon

He's probably got the 10x switch flicked on the probe.
Please post technical questions on the forum, not by personal message. Thanks!

More info:
http://www.gammon.com.au/electronics

ranjeetray


He's probably got the 10x switch flicked on the probe.


Yes , It is 10X probe of Tektronix TDS2024C(200MHz/100MHz, 10MOhm/<12pF 300V CAT II).

ranjeetray

#80
Nov 17, 2012, 05:06 am Last Edit: Nov 17, 2012, 05:28 am by ranjeetray Reason: 1


This code works fine with making SPDR = 0x00; at ISR but I have observed on Oscilloscope that sometime few data goes back to MISO, Slave is not able to clear SPDR perfectly, what could be the reason.


I'm not convinced you read and understood my page here:

http://www.gammon.com.au/spi


In that I mention this exact problem. To get a response you need to allow time for the slave to do whatever it needs to do, and set up a response (ie. set SPDR). See this diagram from that page:



In the code on that page I built in a delay on the master end, to slow down communications long enough to give the slave time to respond. It's all on the page. Please read it again, and again.


Quote
... what could be the reason.


You need to read my page and understand it.


Hi...!!

I am reading http://www.gammon.com.au/spi again and again and trying to grasp SPI, but not getting expected results.

Can we write the codes like this, are these correct codes for mater and slave
Code: [Select]

//Master sending data
#include <SPI.h>// include the SPI library:
#define SCK_PIN   13
#define MISO_PIN  12
#define MOSI_PIN  11

const int spidata = 10;//Pin 11 is data(MOSI) and pin 13 SCK ,set pin 10(SS) as the slave select for the digital pot:
int array[30] = {0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x06, 0x00,0x00, 0x00, 0x00, 0x00, 0x08,0x00, 0x00, 0x00, 0x00, 0x00, 0x0A, 0x00, 0x00, 0x00, 0x00,0x00};
int chr;

void setup() {

 pinMode (spidata, OUTPUT);// set the spi_data_pin as an output:

 SPI.begin();// initialize SPI:
 Serial.begin(115200);
 SPI.setDataMode(SPI_MODE2);
 SPI.setClockDivider(SPI_CLOCK_DIV64) ;
 SPI.setBitOrder(LSBFIRST);
 digitalWrite(spidata,HIGH);

}

void loop() {
 int data[10];
 char ch;


   //delay(14);
  digitalWrite(spidata,LOW);
  SPI.transfer(array[0]);
  SPI.transfer(array[1]);
  digitalWrite(spidata,HIGH);
   //delay(14);
 
  digitalWrite(spidata,LOW);
  SPI.transfer(array[2]);
  SPI.transfer(array[3]);
  digitalWrite(spidata,HIGH);
  // delay(14);
 
  digitalWrite(spidata,LOW);
  SPI.transfer(array[4]);
  SPI.transfer(array[5]);
  digitalWrite(spidata,HIGH);
   delay(1);
 
  digitalWrite(spidata,LOW);
  SPI.transfer(array[6]);
  SPI.transfer(array[7]);
  digitalWrite(spidata,HIGH);
 
    digitalWrite(spidata,LOW);
  SPI.transfer(array[8]);
  SPI.transfer(array[9]);
  digitalWrite(spidata,HIGH);
 
     digitalWrite(spidata,LOW);
  SPI.transfer(array[10]);
  SPI.transfer(array[11]);
  digitalWrite(spidata,HIGH);
 delay(1);
 
    digitalWrite(spidata,LOW);
  SPI.transfer(array[12]);
  SPI.transfer(array[13]);
  digitalWrite(spidata,HIGH);
  // delay(14);
 
  digitalWrite(spidata,LOW);
  SPI.transfer(array[14]);
  SPI.transfer(array[15]);
  digitalWrite(spidata,HIGH);
  // delay(14);
 
  digitalWrite(spidata,LOW);
  SPI.transfer(array[16]);
  SPI.transfer(array[17]);
  digitalWrite(spidata,HIGH);
  delay(1);
 
    digitalWrite(spidata,LOW);
  SPI.transfer(array[18]);
  SPI.transfer(array[19]);
  digitalWrite(spidata,HIGH);
 
     digitalWrite(spidata,LOW);
  SPI.transfer(array[20]);
  SPI.transfer(array[21]);
  digitalWrite(spidata,HIGH);
   digitalWrite(spidata,LOW);
  SPI.transfer(array[22]);
  SPI.transfer(array[23]);
  digitalWrite(spidata,HIGH);
 //  delay(14);
 

   }


Slave receiving data from master then sending the data back to master, is it right.

Code: [Select]

//Slave receiving data from master and sending back data
#include "pins_arduino.h"
#include <SPI.h>
#define SS 10
int dat[24] = {0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14};
byte c;
void ss_falling()
{
 c = 0;
}

void setup (void)
{

 // have to send on master in, *slave out*
 pinMode(MISO, OUTPUT);
 SPI.setBitOrder(MSBFIRST);
 SPI.setDataMode (SPI_MODE2);
 SPI.setClockDivider(SPI_CLOCK_DIV64) ;

 // turn on SPI in slave mode
 SPCR |= _BV(SPE);

 // turn on interrupts
 SPCR |= _BV(SPIE);
 
// disable timer interrupts
 TIMSK0 = 0;
 // interrupt for SS falling edge
 attachInterrupt (0, ss_falling, FALLING);
  // disable timer interrupts
 TIMSK0 = 0;
 
}  // end of setup


// SPI interrupt routine
ISR (SPI_STC_vect)
{
 c = SPDR;
 
if(c == 0x04)
 {
   digitalWrite(SS, LOW);
 SPI.transfer(dat[0]);
 SPI.transfer(dat[1]);
  digitalWrite(SS, HIGH);
 
  digitalWrite(SS, LOW);
 SPI.transfer(dat[2]);
 SPI.transfer(dat[3]);
  digitalWrite(SS, HIGH);
 
  digitalWrite(SS, LOW);
 SPI.transfer(dat[4]);
 SPI.transfer(dat[5]);
  digitalWrite(SS, HIGH);
}

 else if(c == 0x06)
 {
  digitalWrite(SS, LOW);
 SPI.transfer(dat[6]);
 SPI.transfer(dat[7]);
  digitalWrite(SS, HIGH);
 
  digitalWrite(SS, LOW);
 SPI.transfer(dat[8]);
 SPI.transfer(dat[9]);
  digitalWrite(SS, HIGH);
 
  digitalWrite(SS, LOW);
 SPI.transfer(dat[10]);
 SPI.transfer(dat[11]);
  digitalWrite(SS, HIGH);
}
 else
SPDR = 0x00;    // what to return to the master



}  // end of interrupt service routine (ISR) SPI_STC_vect

void loop (void)
{

}  // end of loop



Graynomad

Nick had this

Code: [Select]
// SPI interrupt routine
ISR (SPI_STC_vect)
{
  byte c = SPDR;  // what we received from the master
  SPDR = 0;    // what to return to the master
}  // end of ISR SPI_STC_vect


You have this

Code: [Select]
ISR (SPI_STC_vect)
{
  c = SPDR;
 
if(c == 0x04)
  {
    digitalWrite(SS, LOW);
  SPI.transfer(dat[0]);
  SPI.transfer(dat[1]);
   digitalWrite(SS, HIGH);
   
   digitalWrite(SS, LOW);
  SPI.transfer(dat[2]);
  SPI.transfer(dat[3]);
   digitalWrite(SS, HIGH);
   
   digitalWrite(SS, LOW);
  SPI.transfer(dat[4]);
  SPI.transfer(dat[5]);
   digitalWrite(SS, HIGH);
}

  else if(c == 0x06)
  {
   digitalWrite(SS, LOW);
  SPI.transfer(dat[6]);
  SPI.transfer(dat[7]);
   digitalWrite(SS, HIGH);
   
   digitalWrite(SS, LOW);
  SPI.transfer(dat[8]);
  SPI.transfer(dat[9]);
   digitalWrite(SS, HIGH);
   
   digitalWrite(SS, LOW);
  SPI.transfer(dat[10]);
  SPI.transfer(dat[11]);
   digitalWrite(SS, HIGH);
}
  else
SPDR = 0x00;    // what to return to the master



}  // end of interrupt service routine (ISR) SPI_STC_vect


Do you see the difference?

Nick said this

Quote
The ISR has to be fast, because if you don't change SPDR fast enough, the incorrect data will be sent on the next transfer.


You have an ISR as long as your arm that will take about three weeks to execute.

Nick said this

Quote
you need to allow time for the slave to do whatever it needs to do, and set up a response (ie. set SPDR).


Your code has the odd delay but not after every transfer.

On the master you are toggling the for every two bytes, why?

On the slave you do similar on the SS pin. You DON'T touch the SS pin on the slave. You DON'T call SPI.transfer() on the slave(). You DON'T do nothing on the slave except put data in the SPDR register. If you need to parse the first byte as a command you'd better do it real quick and use the results to point to a different array of bytes to return to the master.


______
Rob
Rob Gray aka the GRAYnomad www.robgray.com

Graynomad

I know I'm going to regret this but here's my quick version of one way to do the slave

Code: [Select]
#define MAX_BYTES 4  // is there 4 bytes? if not change this and the arrays.

byte cmd_04_data[MAX_BYTES] = {1,2,3,4}; // you fill in the numbers
byte cmd_06_data[MAX_BYTES] = {5,6,7,8};
byte * data_ptr;
int byte_count = 0;

ISR (SPI_STC_vect) {
  byte c = SPDR;
  if (byte_count == 0) {
      // set a pointer to one or other array based on the byte just received
      data_ptr = (c == 0x04) ? cmd_04_data : cmd_06_data;
  }
  SPDR = *(data_ptr + byte_count);
  byte_count++;   
  if (byte_count = MAX_BYTES) byte_count = 0;



It compiles but I can't test it.

_____
Rob

Rob Gray aka the GRAYnomad www.robgray.com

ranjeetray


Nick had this

Code: [Select]
// SPI interrupt routine
ISR (SPI_STC_vect)
{
  byte c = SPDR;  // what we received from the master
  SPDR = 0;    // what to return to the master
}  // end of ISR SPI_STC_vect


You have this

Code: [Select]
ISR (SPI_STC_vect)
{
  c = SPDR;
 
if(c == 0x04)
  {
    digitalWrite(SS, LOW);
  SPI.transfer(dat[0]);
  SPI.transfer(dat[1]);
   digitalWrite(SS, HIGH);
   
   digitalWrite(SS, LOW);
  SPI.transfer(dat[2]);
  SPI.transfer(dat[3]);
   digitalWrite(SS, HIGH);
   
   digitalWrite(SS, LOW);
  SPI.transfer(dat[4]);
  SPI.transfer(dat[5]);
   digitalWrite(SS, HIGH);
}

  else if(c == 0x06)
  {
   digitalWrite(SS, LOW);
  SPI.transfer(dat[6]);
  SPI.transfer(dat[7]);
   digitalWrite(SS, HIGH);
   
   digitalWrite(SS, LOW);
  SPI.transfer(dat[8]);
  SPI.transfer(dat[9]);
   digitalWrite(SS, HIGH);
   
   digitalWrite(SS, LOW);
  SPI.transfer(dat[10]);
  SPI.transfer(dat[11]);
   digitalWrite(SS, HIGH);
}
  else
SPDR = 0x00;    // what to return to the master



}  // end of interrupt service routine (ISR) SPI_STC_vect


Do you see the difference?

Nick said this

Quote
The ISR has to be fast, because if you don't change SPDR fast enough, the incorrect data will be sent on the next transfer.


You have an ISR as long as your arm that will take about three weeks to execute.

Nick said this

Quote
you need to allow time for the slave to do whatever it needs to do, and set up a response (ie. set SPDR).


Your code has the odd delay but not after every transfer.

On the master you are toggling the for every two bytes, why?

On the slave you do similar on the SS pin. You DON'T touch the SS pin on the slave. You DON'T call SPI.transfer() on the slave(). You DON'T do nothing on the slave except put data in the SPDR register. If you need to parse the first byte as a command you'd better do it real quick and use the results to point to a different array of bytes to return to the master.


______
Rob

Hi...!!!

Thanks. More than two SPI.transfer(); does not work fine and 2 bytes of data transfer gives continuous 16clock pulse.
Following code does not work fine with SPDR = data; and I want to send back more than 10 data. And I am not able to give proper delay.
Can you please tell me how much delay I should give at Master side or Slave side.

Code: [Select]

#include "pins_arduino.h"
#include <SPI.h>
#define SS 10
int dat[24] = {0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14};
byte c;
void ss_falling()
{
 c = 0;
}

void setup (void)
{

 // have to send on master in, *slave out*
 pinMode(MISO, OUTPUT);
 SPI.setBitOrder(MSBFIRST);
 SPI.setDataMode (SPI_MODE2);
 SPI.setClockDivider(SPI_CLOCK_DIV64) ;

 // turn on SPI in slave mode
 SPCR |= _BV(SPE);

 // turn on interrupts
 SPCR |= _BV(SPIE);
 
// disable timer interrupts
 TIMSK0 = 0;
 // interrupt for SS falling edge
 attachInterrupt (0, ss_falling, FALLING);
  // disable timer interrupts
 TIMSK0 = 0;
 
}  // end of setup


// SPI interrupt routine
ISR (SPI_STC_vect)
{
 c = SPDR;
 
 if(c == 0x04)
 {
   
   SPDR = dat[0];
 
}

  else if(c == 0x06)
 {
   SPDR = dat[1];
 
}
 else
SPDR = 0x00;    // what to return to the master



}  // end of interrupt service routine (ISR) SPI_STC_vect

void loop (void)
{

}  // end of loop



ranjeetray


I know I'm going to regret this but here's my quick version of one way to do the slave

Code: [Select]
#define MAX_BYTES 4  // is there 4 bytes? if not change this and the arrays.

byte cmd_04_data[MAX_BYTES] = {1,2,3,4}; // you fill in the numbers
byte cmd_06_data[MAX_BYTES] = {5,6,7,8};
byte * data_ptr;
int byte_count = 0;

ISR (SPI_STC_vect) {
  byte c = SPDR;
  if (byte_count == 0) {
      // set a pointer to one or other array based on the byte just received
      data_ptr = (c == 0x04) ? cmd_04_data : cmd_06_data;
  }
  SPDR = *(data_ptr + byte_count);
  byte_count++;   
  if (byte_count = MAX_BYTES) byte_count = 0;



It compiles but I can't test it.

_____
Rob




Hi..!!

This code gives following result, which is attached here, blue line is MISO yellow MOSi and Pink line is SCK.

Code: [Select]

#define MAX_BYTES 4  // is there 4 bytes? if not change this and the arrays.

byte cmd_04_data[MAX_BYTES] = {1,2,3,4}; // you fill in the numbers
byte cmd_06_data[MAX_BYTES] = {5,6,7,8};
byte * data_ptr;
int byte_count = 0;
void setup (void)
{
}
ISR (SPI_STC_vect) {
  byte c = SPDR;
  if (byte_count == 0) {
      // set a pointer to one or other array based on the byte just received
      data_ptr = (c == 0x04) ? cmd_04_data : cmd_06_data;
  }
  SPDR = *(data_ptr + byte_count);
  byte_count++;   
  if (byte_count = MAX_BYTES) byte_count = 0;
}
void loop (void)
{

}  // end of loop

Graynomad

That wasn't a stand-alone program, what happened to all your setup() code (most or which you don't need anyway I think).

______
Rob
Rob Gray aka the GRAYnomad www.robgray.com

ranjeetray

#86
Nov 17, 2012, 06:32 am Last Edit: Nov 17, 2012, 06:44 am by ranjeetray Reason: 1
Code: [Select]
[code][quote author=Nick Gammon link=topic=120454.msg999023#msg999023 date=1353098493]
[quote author=ranjeetray link=topic=120454.msg998331#msg998331 date=1353063009]
Can we do like this, after receiving data can we check(if condition) data and then send back data to master like this.
[/quote]

I really don't know what you are trying to do. You are doing an SPI.transfer in the middle of the ISR?

You send back data to the master [b]by assigning to SPDR in the interrupt service routine[/b]. No other way. What are you thinking?
[/quote]

Hi...!!

This way(SPDR = dat[0]) also it is not able to send back data to Master, and I am not able to give delay properly and synchronize with master. Slave is not getting chance to send back data, I think so.


[code]

#include "pins_arduino.h"
#include <SPI.h>
#define SS 10
int dat[24] = {0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14};
byte c;
void ss_falling()
{
 c = 0;
}

void setup (void)
{

 // have to send on master in, *slave out*
 pinMode(MISO, OUTPUT);
 SPI.setBitOrder(MSBFIRST);
 SPI.setDataMode (SPI_MODE2);
 SPI.setClockDivider(SPI_CLOCK_DIV64) ;

 // turn on SPI in slave mode
 SPCR |= _BV(SPE);

 // turn on interrupts
 SPCR |= _BV(SPIE);
 
// disable timer interrupts
 TIMSK0 = 0;
 // interrupt for SS falling edge
 attachInterrupt (0, ss_falling, FALLING);
  // disable timer interrupts
 TIMSK0 = 0;
 
}  // end of setup


// SPI interrupt routine
ISR (SPI_STC_vect)
{
 c = SPDR;
 
 if(c == 0x04)
 {
   
   SPDR = dat[0];
 
}

  else if(c == 0x06)
 {
   SPDR = dat[1];
 
}
 else
SPDR = 0x00;    // what to return to the master



}  // end of interrupt service routine (ISR) SPI_STC_vect

void loop (void)
{

}  // end of loop

[/code][/code]

ranjeetray


That wasn't a stand-alone program, what happened to all your setup() code (most or which you don't need anyway I think).

______
Rob


Hi..!!

This code give following results, which have been attached here.

Code: [Select]



#include "pins_arduino.h"
#include <SPI.h>

#define MAX_BYTES 4  // is there 4 bytes? if not change this and the arrays.

byte cmd_04_data[MAX_BYTES] = {1,2,3,4}; // you fill in the numbers
byte cmd_06_data[MAX_BYTES] = {5,6,7,8};
byte * data_ptr;
int byte_count = 0;
void setup (void)
{
 
  // have to send on master in, *slave out*
  pinMode(MISO, OUTPUT);
  SPI.setBitOrder(MSBFIRST);
  SPI.setDataMode (SPI_MODE2);
  SPI.setClockDivider(SPI_CLOCK_DIV64) ;

  // turn on SPI in slave mode
  SPCR |= _BV(SPE);

  // turn on interrupts
  SPCR |= _BV(SPIE);
 
// disable timer interrupts
  TIMSK0 = 0;
  // interrupt for SS falling edge
  //attachInterrupt (0, ss_falling, FALLING);
   // disable timer interrupts
  TIMSK0 = 0;
}
ISR (SPI_STC_vect) {
  byte c = SPDR;
  if (byte_count == 0) {
      // set a pointer to one or other array based on the byte just received
      data_ptr = (c == 0x04) ? cmd_04_data : cmd_06_data;
  }
  SPDR = *(data_ptr + byte_count);
  byte_count++;   
  if (byte_count = MAX_BYTES) byte_count = 0;
}
void loop (void)
{

}  // end of loop

Graynomad

I can't make out anything from the scope screen shots, there's obviously something happening though.

Tell you what I'll do, against my better judgement I'll try to write you some code for both ends based on what I think you want to do.

______
Rob
Rob Gray aka the GRAYnomad www.robgray.com

ranjeetray


That wasn't a stand-alone program, what happened to all your setup() code (most or which you don't need anyway I think).

______
Rob


Hi..!!

With this code , attached result is coming.

Code: [Select]


#include "pins_arduino.h"
#include <SPI.h>

#define size_data 4  // is there 4 bytes? if not change this and the arrays.

byte send_04_data[size_data] = {1,2,3,7}; // you fill in the numbers
byte send_06_data[size_data] = {3,8,7,9};
byte * data_ptr;
int byte_count = 0;
void setup (void)
{
 
  // have to send on master in, *slave out*
  pinMode(MISO, OUTPUT);
  SPI.setBitOrder(MSBFIRST);
  SPI.setDataMode (SPI_MODE2);
  SPI.setClockDivider(SPI_CLOCK_DIV64) ;

  // turn on SPI in slave mode
  SPCR |= _BV(SPE);

  // turn on interrupts
  SPCR |= _BV(SPIE);
 
// disable timer interrupts
  TIMSK0 = 0;
  // interrupt for SS falling edge
  //attachInterrupt (0, ss_falling, FALLING);
   // disable timer interrupts
  TIMSK0 = 0;
}
ISR (SPI_STC_vect) {
  byte c = SPDR;
  if (byte_count == 0)
  {
     
      data_ptr = (c == 0x04) ? send_04_data : send_06_data;
 
  SPDR = *(data_ptr + byte_count);
  byte_count++; } 
  else
 
  {
    SPDR = 0;      //******** Added
 
  }
  if (byte_count = size_data)
  byte_count = 0;
}
void loop (void)
{

}  // end of loop

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