I know this is about eeproms but it is a software question.
I am using the AT24c256 library and the example that comes with it.
/**
* This sketch shows examples on how to use all the features of this library
*
* It can also be used as a test to verify that you have your eprom configured
* propery to your Arduino as it prints out the results so you can see if everything works
*/
#include <at24c256.h>
// Create a eprom object configured at address 0
// Sketch assumes that there is an eprom present at this address
AT24C256 eprom(AT24C_ADDRESS_0);
// Create another eprom object configured att address 2
// Sketch assumes that there is NO eprom present at this address
AT24C256 badEprom(AT24C_ADDRESS_2);
void setup() {
Serial.begin(115200);
Serial.println("Starting up");
// Initialize the i2c library
Wire.begin();
/** Write and read an integer */
int foo = 42;
// Write the integer foo to the eprom starting at address 0
eprom.put(0, foo);
int foo_in;
// Read the integer foo_in from eprom starting at address 0
eprom.get(0, foo_in);
Serial.println(foo_in);
/** Write and read a double */
double pi = 3.141593;
// Write the double pi to the eprom starting at address 0
eprom.put(0, pi);
double pi_in;
// Read the double pi_in from eprom starting at address 0
eprom.get(0, pi_in);
// Create a buffer and convert pi_in to a string to be able to print it
char buffer[10];
dtostrf(pi_in, 9, 6, buffer); // Converts a double to a string
Serial.println(buffer);
/** Write and read a struct */
// Declare the struct "Point"
struct Point {
int x;
int y;
};
Point point = {17, 42};
// Write the struct point to the eprom starting at address 0
eprom.put(0, point);
Point point_in;
// Read the struct point_in from eprom starting at address 0
eprom.get(0, point_in);
Serial.println(point_in.x);
Serial.println(point_in.y);
/** Write and read a single byte */
// Write the value 77 to the eprom byte at address 0
eprom.write(0, 77);
// Read the value of the byte at address 0
int value = eprom.read(0);
Serial.println(value);
/** Write and read a byte buffer */
uint8_t out[15] = "Test of buffer";
// Write the 15 bytes long buffer "out" to eprom starting at address 0
eprom.writeBuffer(0, out, 15);
uint8_t in[15];
// Read 15 bytes from eprom starting at address 0 into the buffer "in".
eprom.readBuffer(0, in, 15);
Serial.println((char*)in);
/** Error handling on write, no error */
// Read a byte from address 0, this should not result in an error
eprom.write(0, 77);
// Get the last error code, it should be 0 since there was no error
int lastError = eprom.getLastError();
Serial.print("last status on write: ");
Serial.println(lastError);
/** Error handling on write, using a eprom address without eprom */
// Write the value 77 to an eprom that is not connected - this will fail
badEprom.write(0, 77);
// Get the last error code, it should not be zero, but 2 which means that there were no response from the eprom
int lastError2 = badEprom.getLastError();
Serial.print("last error on write: ");
Serial.println(lastError2);
/** Error handling on read, using a eprom address without eprom */
// Read the value from address 0 from an eprom that is not connected (and print it)
badEprom.read(0);
// Get the last error code, it should not be zero, but 2 which means that there were no response from the eprom
int lastError3 = badEprom.getLastError();
Serial.print("last error on read: ");
Serial.println(lastError3);
// Read the size of the eprom and print it
Serial.println(eprom.length());
/** Write and read a long byte buffer, >32 which is TwoWire's internal buffer size and
* >64 which is the at24c256 page size) */
uint8_t out2[80] = "Writing a really long message, testing some of several buffer limits on the way";
// Write the long buffer to the eprom starting at address 0 and check how many bytes were actually written
int written = eprom.writeBuffer(0, out2, 80);
Serial.print(written);
Serial.print(" bytes written, last error on write: ");
// Get the last error and print it
Serial.println(eprom.getLastError());
uint8_t in2[80];
// Read 80 bytes from eprom starting at address 0 and store it in the in2 buffer. Check how many bytes were actually read
int readBytes = eprom.readBuffer(0, in2, 80);
Serial.print(readBytes);
Serial.print(" bytes read, last error on read: ");
// Get the last error and print it
Serial.println(eprom.getLastError());
in2[79] = '\0';
Serial.println((char*)in2);
}
// This test program has no loop, it just runs once
void loop() {
}
I have cut it down to
/**
* This sketch shows examples on how to use all the features of this library
*
* It can also be used as a test to verify that you have your eprom configured
* propery to your Arduino as it prints out the results so you can see if everything works
*/
#include <at24c256.h>
// Create a eprom object configured at address 0
// Sketch assumes that there is an eprom present at this address
AT24C256 eprom(AT24C_ADDRESS_0);
// Create another eprom object configured att address 2
// Sketch assumes that there is NO eprom present at this address
AT24C256 badEprom(AT24C_ADDRESS_2);
void setup() {
Serial.begin(115200);
Serial.println("Starting up");
// Initialize the i2c library
Wire.begin();
/** Write and read a byte buffer */
uint8_t outa[15] = "Test of buffer";
// Write the 15 bytes long buffer "out" to eprom starting at address 0
eprom.writeBuffer(0, outa, 15);
uint8_t outb[15] = "Tess of buffer";
// Write the 15 bytes long buffer "out" to eprom starting at address 0
eprom.writeBuffer(8, outb, 15);
// Read 15 bytes from eprom starting at address 0 into the buffer "in".
uint8_t ina[15];
eprom.readBuffer(0, ina, 15);
Serial.println((char*)ina);
uint8_t inb[15];
eprom.readBuffer(8, inb, 15);
Serial.println((char*)inb);
}
// This test program has no loop, it just runs once
void loop() {
}
This should now just load the line
'Test of Buffer'
into address 0 and
'Tess of buffer'
into address 8
I thought I would get
'Test of Tess of
Tess of buffer'
since the second one over writes the first but I get
'Test of Tess of buffer
Tess of buffer'
Should it not just give me the first 15 letters on the first line since I am only asking for ina to read the first 15 addresses? why does it give me 24?
