Issue in changing data format (2 bytes) into a 16 bit data.

[GiggsB]

What does struct.unpack() return? Have you read the documentation for the struct library? The answer is there.

Got it! Thank you. I changed the "I" to "H" which is for unsigned short (2 bytes) and I was able to receive the values combining every 2 bytes. But I got stuck into this tricky part where I only want to write every other value in the file. For example, write value[0], ignore value[1], write value[2], and so on...To work on this, I made the following change, but now the data is not being written into the file at all...any hints?

def spi_process(gpio,level,tick):
    data = bytes([0]*2048)
    spi.xfer2([0x02])
    for x in range(1):
        recv = spi.xfer2(data)
        values = struct.unpack(">" +"H"*1024, bytes(recv))
        f.write("\n")
        num=1
        while num in range(0,2047):
            if num%2==0:
                f.write("\n")
                f.write(str(x))

[deanhystad]

I would try something like this:

def spi_process(*_):
    spi.xfer2([0x02])
    data_bytes = bytes(spi.xfer2([0]*2048))
    num_shorts = len(data_bytes) // 2
    data_short = struct.unpack(f">{num_shorts}H", data_bytes)
    # Write every other short to a file
    for index in range(0, num_shorts, 2):
        f.write(f"{data_short[index]}\n")

Or if you prefer unpacking to long and using shift.

def spi_process(*_):
    spi.xfer2([0x02])
    data_bytes = bytes(spi.xfer2([0]*2048))
    num_long = len(data_bytes) // 4
    for value in struct.unpack(f">{num_long}L", data_bytes):
        f.write(f"{value >> 16}\n")

I have not tested this code at all. I can't even install the spidev package.

Why aren't you using read_bytes() and write_bytes()?