Meaning of code

[MBB]

Does anyone know what this code means:

float Adafruit_seesaw::getTemp() {
uint8_t buf[4];
this->read(SEESAW_STATUS_BASE, SEESAW_STATUS_TEMP, buf, 4, 1000);
int32_t ret = ((uint32_t)buf[0] << 24) | ((uint32_t)buf[1] << 16) |
((uint32_t)buf[2] << 8) | (uint32_t)buf[3];
return (1.0 / (1UL << 16)) * ret;
}

or in python this:

def get_temp(self):
    """Read the temperature"""
    buf = bytearray(4)
    self.read(_STATUS_BASE, _STATUS_TEMP, buf, 0.005)
    buf[0] = buf[0] & 0x3F
    ret = struct.unpack(">I", buf)[0]
    return 0.00001525878 * ret

[Anobium]

The C conversion follows.

The real question would be ... what is the sensor and how do you get the result with integer maths.. So, what is the sensor?

Evan

function getTemp as Long
Dim buf(4) at GetTemp
//! This is another routine called read()
  //! SEESAW_STATUS_BASE  - some constant value
  //! SEESAW_STATUS_TEMP  - some constant value
  //! buf()               - the array/buffer being used to pass the data
  //! 4                   - the size of the array/buffer - my guess
  //! 1000                - a timeout - my guess
  //!
  //! return range is unknown.
read( SEESAW_STATUS_BASE, SEESAW_STATUS_TEMP, buf(), 4, 1000)

//! build up a the return..
//! Note array starts at element 1 
//!  equates to getemp_E = buf(1)
//!  equates to getemp_U = buf(2)
//!  equates to getemp_H = buf(3)
//!  equates to getemp = buf(4)
int32_t ret = ((uint32_t)buf[0] << 24) | ((uint32_t)buf[1] << 16) |
((uint32_t)buf[2] << 8) | (uint32_t)buf[3];

//! return the value...
//!  1UL << 16 means:
/*
  1UL is 1 as an unsigned long integer
  << 16 shifts it left by 16 bits
  This is equivalent to multiplying by 2^16
  2^16 = 65,536


  So 1UL << 16 = 65,536
  Now we're calculating 1.0 / 65,536
  This equals approximately 0.0000152587890625

The exact result is 1/65,536 = 0.0000152587890625 (this is precise as it's a power of 2 division)
*/
  return (1.0 / (1UL << 16)) * ret;

end Sub

[MBB]

Thanks!

I'm using this board https://www.adafruit.com/product/3657