Thread: Count number of 1 in a binary data trame through the serial port DB9

Normal asynchronous serial ports (RS232 compatible for example) give you 8 bits of data at a time, in a packet of 10 bits of start + 8 data + stop bits. If you receive a 8-bit data packet, you can of course count the number of ones in it:

Code:

int count = 0;
unsigned char data = DataFromSerialPort();
for(i = 0; i < 8;i++)
{
  count += data & 1;
  data >>= 1;
}

(There are ways to do a table that holds for example 16 values, with the corresponding number of 1s of each 4-bit half of an 8 bit number, which speeds up the process a bit. But it's a lot more to write].

--
Mats

If on UNIX, open the device file that corresponds to the serial port, read data from it and bitwise AND it with the binary equivalent of the RxD pin set.

Originally Posted by itCbitC

If on UNIX, open the device file that corresponds to the serial port, read data from it and bitwise AND it with the binary equivalent of the RxD pin set.

Huh?
Reading the device-file will give you, a byte at a time, from the serial port's RxD pin - since that's the pin that receives the data from the other end. There is no need for any AND operation in this place. Of course, to count the number of 1s, we'd have to use the AND operator (at least, if we use the method from above).

--
Mats