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// ---------------------------------
// Stress test program/example for TinyWireS I2C library.
// Run this slave program on the Attiny.
// Run the other master program on the Arduino Uno R3.
// ---------------------------------
// // Written by Scott Hartog, 2/6/2016, to stress test the TinyWireS library.
// https://github.com/rambo/TinyWire
//
// This project uses the Tiny85 as an I2C slave.
//
// The slave program using TinyWireS, running on a Attiny85, receives
// N bytes of random data in a single receiveEvent() callback and
// stores that data in a global buffer. It then responds the first requestEvent()
// callback with that same data. The requestEvent() callback overwrites the data
// buffer with zeros after responding so it will only respond correctly to the
// first requestEvent() callback after each receiveEvent() callback. Subsequent
// requestEvent() will respond with 0xff for all data bytes.
//
//
// SETUP:
// AtTiny Pin 5 (PB0/SDA) = I2C SDA
// connect to SDA on master with external pull-up (~4.7K)
// AtTiny Pin 7 (PB0/SCL) = I2C SCL
// connect to SCL on master with external pull-up (~4.7K)
// AtTiny Pin 1 (PB5/!RST)
// connect to reset on master (or just pull-up)
//
// Please see credits and usage for usiTwiSlave and TinyWireS in the .h files of
// those libraries.
#include "TinyWireS.h" // wrapper class for I2C slave routines
#define I2C_SLAVE_ADDR 0x26 // i2c slave address (38, 0x26)
// global buffer to store data sent from the master.
uint8_t master_data[16];
// global variable to number of bytes sent from the master.
uint8_t master_bytes;
const int LEDPin = 4; //pin 4 arduino, pin 3 on ATTiny85)
const int FanPin = 1; // pin 1 arduino, pin 6 on ATtiny85)
// Gets called when the ATtiny receives an i2c write slave request
void receiveEvent(uint8_t num_bytes)
{
uint8_t i;
// save the number of bytes sent from the master
master_bytes = num_bytes;
// store the data from the master into the data buffer
for (i = 0; i < master_bytes; i++)
master_data[i] = TinyWireS.receive();
analogWrite(FanPin, master_data[0]);
analogWrite(LEDPin, master_data[1]);
}
// Gets called when the ATtiny receives an i2c read slave request
void requestEvent()
{
uint8_t i;
// send the data buffer back to the master
for (i = 0; i < master_bytes; i++)
TinyWireS.send(master_data[i]);
// corrupt the byte values in the data buffer
// so that subsequent call won't match
for (i = 0; i < master_bytes; i++)
master_data[i] += 0x5a;
// corrupt length of the request, but dont' make it zero
// if the usiTwiSlave.c is working fine, then this number is completely irrelevant
// because the requestEvent() callback will not be called again until
// after the next receiveEvent() callback, so the master_data and
// master_bytes variables will be set by that call.
// If the usiTwiSlave.c has the issue of calling the requestFrom() callback
// for each byte sent, the buffer will accumulate by this amount *for each byte
// in the original request*.
//
// Making it zero will obscure the 1-byte send issue in the usiTwiSlave.c
// that is being tested.
// Making it small will allow a few requests to succeed before the tx buffer
// overflows and the usiTwiSlave.c hangs on the "while ( tmphead == txTail );"
// line
master_bytes = 2;
}
void setup()
{
// initialize the TinyWireS and usiTwiSlave libraries
TinyWireS.begin(I2C_SLAVE_ADDR); // init I2C Slave mode
// register the onReceive() callback function
TinyWireS.onReceive(receiveEvent);
// register the onRequest() callback function
TinyWireS.onRequest(requestEvent);
pinMode(LEDPin, OUTPUT);
pinMode(FanPin, OUTPUT);
TCCR0B = TCCR0B & 0b11111000 | 0b001; // Sets internal timer to 31250 Hz, and PWM frequency on PB0 (Arduino pin 4) to 31250 Hz, fast enough for a fan!
//analogWrite(FanPin, FanPwm);
//analogWrite(LEDPin, LEDPwm);
}
void loop()
{
// This needs to be here
TinyWireS_stop_check();
// otherwise empty loop
}
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