How do I represent a byte array position value into binary string?

Don M · 2021-03-10 22:38

Let's say I have a byte array of 16 bytes and also a 2 byte array. If any one of those 16 bytes is an $FF then I would want the corresponding position of one of the bits set in the 2 byte array. I know it's hard to explain.

Byte array of 16: $00, $03, $05, $FD, $FF, $FF, $EE, $FF, $09, $00, $03, $05, $FD, $FF, $50, $09
then the 2 byte array would look like this in binary: 0000 1101 0000 01000

So how do I go about testing the bytes in the array and then setting a bit in the 2 byte array (or 1 word) if it's an $FF?

dgately · 2021-03-10 23:35

@"Don M" said:
Let's say I have a byte array of 16 bytes and also a 2 byte array. If any one of those 16 bytes is an $FF then I would want the corresponding position of one of the bits set in the 2 byte array. I know it's hard to explain.

Byte array of 16: $00, $03, $05, $FD, $FF, $FF, $EE, $FF, $09, $00, $03, $05, $FD, $FF, $50, $09
then the 2 byte array would look like this in binary: 0000 1101 0000 01000

So how do I go about testing the bytes in the array and then setting a bit in the 2 byte array (or 1 word) if it's an $FF?

In spin (probably much more efficient ways to do this, but this explains how):

'' Test  RE:  https://forums.parallax.com/discussion/173110/how-do-i-represent-a-byte-array-position-value-into-binary-string

con
  _clkmode = xtal1 + pll16x
  _clkfreq = 80_000_000

obj
    term : "fullduplexserial"

var
    byte arrayBytes[16]
    word bitArray

dat
    dataBytes byte  $00, $03, $05, $FD, $FF, $FF, $EE, $FF, $09, $00, $03, $05, $FD, $FF, $50, $09 


pub main() | idx, mask

  term.start(63, 62, 0, 115_200)            '' terminal setup
  term.str(string("Testing..."))
  term.tx(13)
  term.tx(10)

  bytemove(@arrayBytes, @dataBytes, 16)

    repeat idx from 15 to 0
        if arrayBytes[idx] == $FF
            mask := 1 << (15 - idx)
            bitArray |= mask

    term.bin(bitArray, 16)

Downloading file to port /dev/cu.usbserial-DN02MWJI
2664 bytes sent                  
Verifying RAM
Download successful!
[ Entering terminal mode. Type ESC or Control-C to exit. ]
Testing...
0000110100000100

dgately

Don M · 2021-03-11 00:39

Thanks. Much appreciated.

Don M · 2021-03-11 00:59

One more question.. leaving the dataBytes in the order they are in your example how do I reverse the order in the bitArray so it comes out 0010000010110000 ? I tried reversing the "repeat idx from 15 to 0" to "0 to 15" but it was still the same.

Don M · 2021-03-11 01:01

Figured it out. Changed mask := 1 << (15 - idx) to mask := 1 << ( idx)

Thanks.

dgately · 2021-03-11 01:56

@"Don M" said:
Figured it out. Changed mask := 1 << (15 - idx) to mask := 1 << ( idx)

Thanks.

Welcome...

How do I represent a byte array position value into binary string?

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