From the Arduino playground documentation for the Nrf2401 library, the .write method accepts either: a byte to transmit, a pointer to your unsigned char buffer; or a void argument meaning use the library's internal buffer. You must have called the .txmode() method first.

Since you're trying to use your own buffer, you'll need to make it long enough to contain the message you want to transmit (plus one byte for the terminating NUL). You'll need a character representation of the value you want to send, not the binary number itself. At a quick read of the library doc I didn't see the message format the library wants, but assuming it's something like: T<space>12.34<newline>, you'll need something like this (untested, it may need tweaking)

sprintf(data, "T %f5.2\n, currentTemp);   // build command in data[]
radio.txMode(strlen(data));               // set # bytes to xmit
radio.write(data);                        // send bytes

From the Arduino playground documentation for the Nrf2401 library, the .write method accepts either: a byte to transmit, a pointer to your unsigned char buffer; or a void argument meaning use the library's internal buffer. You must have called the .txmode() method first.

Since you're trying to use your own buffer, you'll need to make it long enough to contain the message you want to transmit (plus one byte for the terminating NUL). You'll need a character representation of the value you want to send, not the binary number itself. At a quick read of the library doc I didn't see the message format the library wants, but assuming it's something like: T<space>12.34<newline>, you'll need something like this (untested, it may need tweaking)

sprintf(data, "T %5.2f\n", currentTemp);  // build command in data[]
radio.txMode(strlen(data));               // set # bytes to xmit
radio.write(data);                        // send bytes