Sending long variables via I2C but only 16bit for long as result

hi all,

i connected 2 arduinos unos via i2c , need send long variables. therefor convert long byte array , send it.

my problem re-conversion correctly received 4 bytes long variable:

here code fragment:

code: [select]

  readbytes(arduino_slave_i2c_address, 8 , &rawdata[0]); // read 8  raw data bytes
  long myvariable =(  (rawdata[0] << 24) | (rawdata[1] << 16) | rawdata[2]<<8 | rawdata[3] );   // turn bytes signed 32-bit value

  serial.print(rawdata[0],bin);serial.print(" ");serial.print(rawdata[1],bin);serial.print(" ");serial.print(rawdata[2],bin);serial.print(" ");serial.println(rawdata[3],bin);
  serial.println(test, bin);
  serial.println(test, dec);

this gives this:

quote

11 101100 1010000 10101000
101000010101000
20648

so bytes correct, controlled it! long number should "53235880"
but why have 16 bit long? googled lot did not find solution :-/

all best
tim

integer expressions evaluated ints, if no operand long.

you cast bytes shifting unsigned longs.

code: [select]

long myvariable =(  (((unsigned long)rawdata[0]) << 24) | (((unsigned long)rawdata[1]) << 16) | (((unsigned long)rawdata[2])<<8) | rawdata[3] );

Arduino Forum > Using Arduino > Networking, Protocols, and Devices (Moderator: fabioc84) > Sending long variables via I2C but only 16bit for long as result

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