On 07Sep2018 15:45, Chip Wachob <wach...@gmail.com> wrote:
Basically I'm trying to write a block of unsigned bytes to the device
and read back an equal sized block of unsigned bytes. There's a
function that is provided called transfer(data_to_send, num_of_bytes)
that handles the heavy lifting. Unfortunately there seems to be a bug
in the part and if I attempt to send the entire block of bytes (64),
the device will lock up. I've been able to determine that if I send
16 bytes at a time, I'm okay.
So, I take my bytearray(64) and step through it 16 bytes at a time like this:
my function's main pieces are:
def transfer_byte_array():
MAX_LOOP_COUNT = 64
slice_size = 16
read_ary = bytearray(MAX_LOOP_COUNT)
scratch_ary = bytearray()
for step in range (0, MAX_LOOP_COUNT, slice_size):
scratch_ary = transfer(data_to_send, slice_size)
for bytes in range (0, slice_size):
read_ary = scratch_ary[bytes]
return(read_ary)
Ideally, I'd like to take the slice_size chunks that have been read
and concatenate them back togetjer into a long MAX_LOOP_COUNT size
array to pass back to the rest of my code. Eg:
read_ary = ary_slice[0] + ary_slice[1] + ary_slice[2] + ary_slice[3]
Minor remark: don't use the name "bytes" for a variable, it is a builtin type
name and you're shadowing it.
It looks to me like "transfer" hands you back a buffer with the read data, so
this:
scratch_ary = bytearray()
don't do anything (it gets discarded).
If you're getting back a bytes or bytearray object from transfer, just gather
them all up in an list:
returned_buffers = []
for ......
response = transfer(data_to_send, slice_size)
returned_buffers.append(response)
.......
read_ary = b''.join(returned_buffers)
Note that that makes a new bytes object for read_ary to refer to. You don't
need the earlier initialisation of read_ary.
Also note that the bytes object is read only; if that is a problem you'll need
to construct a bytearray instead.
[...]
The problem that I repeatedly run into is with the line:
read_ary = scratch_ary[bytes] (or variants thereof)
The traceback is this:
Traceback (most recent call last):
File "SW8T_5.py", line 101, in <module>
loop_size = RSI_size_the_loop(Print)
File "/home/temp/Python_Scratch/examples/RSI.py", line 350, in
RSI_size_the_loop
read_ary.append(scratch_ary[singles])
TypeError: an integer or string of size 1 is required
Yeah I thought that looked weird to me too.
or, one of the other common ones that I've seen is
TypeError: can't concat bytearray to list
This one is confusing because both of the operands are bytearry
types.. or at least I thought they should be...
No, one will be a list :-) putting a bunch of:
print(repr(foo))
replacing "foo" with relevant variables will be illuminating to you; you can
see immediately where this are not what you expected.
I'm obviously missing something fundamental here. Problem is I can't
seem to find any examples of people asking this question before on the
inter-webs..
You have the opposite of my problem. I can often find people asking the same
question, but less often an answer. Or a decent answer, anyway.
Cheers,
Cameron Simpson <c...@cskk.id.au>
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