How to write 16bit integer to SRAM via Arduino? - arduino

Question

The base of the problem: I have an Arduino Due and a MPU6050 accelerometer and an 23lcv512. MPU gives me 16bit signed integer. I would like to save the datas to the SRAM and after the measurement read them back and via Serial send it to PC. Sending to PC is not a problem. The problem is that this SRAM has 128k pcs 8bit address. My numbers are 16 bit. I can't write them directly. Here is my code. I tested the RAM with this code:
`
void loop() {
int i = 0;
Serial.print("Write Byte: ");
for (i = 0; i < 70000; i++) {
//Serial.print("Write Byte: ");
//Serial.print(i);
//Serial.println();
SRAM.writeByte(START_ADDRESS, i);
START_ADDRESS = START_ADDRESS + 1;
}
Serial.print("Write End");
i = 0;
START_ADDRESS = 0;
for (i = 0; i < 300; i++) {
Serial.print("Read Byte: ");
Serial.print(SRAM.readByte(START_ADDRESS));
Serial.println();
Serial.println();
START_ADDRESS = START_ADDRESS + 1;
delay(100);
}
}`
I added the 23LC library. If it's run reads back the numbers from the RAM but after 255 it starts to read 0 again. I know why does it happen. But I don't know howto solve the problem.
I tried to use the writeBlock command but it only works for me with char variables. Char variable requires more space than integers. I have not too much.
Is there anyone who can write a sample code which can write 16 bit signed integer to sram?

Answer 1

I've commented the most obvious problems in your original code below:
void loop() {
int i = 0;
Serial.print("Write Byte: ");
for (i = 0; i < 70000; i++) { // since i is a 16bit int, 70,000 is out of range.
SRAM.writeByte(START_ADDRESS, i); // cool you wrote 1 byte, where is the other write?
START_ADDRESS = START_ADDRESS + 1; // try to keep all caps names for constants.
// this will make your code easier to read, trust me!
}
Serial.print("Write End");
i = 0;
START_ADDRESS = 0;
for (i = 0; i < 300; i++) {
Serial.print("Read Byte: ");
Serial.print(SRAM.readByte(START_ADDRESS)); // you read 1 byte, you can't expect a 16 bit
// value out of that.
Serial.println();
Serial.println();
START_ADDRESS = START_ADDRESS + 1;
delay(100);
}
}
Here's a more sound approach, it stores unsigned ints, but that can easily be changed to signed ints.
#define SRAM_SIZE (128UL << 10) // we have 128K of SRAM available.
// The U and L make this value an unsigned long.
// ALWAYS use unsigned values for addresses.
void loop()
{
Serial.print(F("Writing sequential numbers into SRAM...")); // _always_ store string constants in flash.
// save your RAM for more interesting stuff.
for (unsigned long i = 0; i < SRAM_SIZE; i += 2) // filling SRAM
{
// this is the (truncated from 0-65535) value we'll write.
unsigned int value = static_cast<unsigned int>(i & 0xFFFF);
SRAM.writeByte(i, value & 0xFF); // write lowest 8 bits
SRAM.writeByte(i + 1, (value >> 8) & 0xFF); // write next 8 bits.
}
Serial.println(F("done."));
// read back
Serial.println(F("SRAM contents (16-bits unsigned values):"));
for (unsigned long i = 0; i < SRAM_SIZE; i += 2) // reading all SRAM in 16-bit chunks.
{
Serial.print(i, HEX);
Serial.print(F(": "));
// read two consecutive bytes and pack them into a 16-bit integer.
unsigned int value = SRAM.readByte(i) + (static_cast<unsigned int>(SRAM.readByte(i+1)) << 8); // the cast is necessary.
Serial.println(value);
}
delay(100);
}