Sorry, not what i meant at all (I get terser as midnight approaches, ha!)
You are only reading 64 bytes from flash, which is 16 32-bit ints, so your
result is entirely expected. The rest of the data array is uninitialised.
Correct code would look something like this:
uint32_t data[64 >> 2];
...
bytes_to_read = min(64, fa->fa_size - data_off);
flash_area_read(fa, data_off, data, bytes_to_read);
...
for (i = 0; i < bytes_to_read >> 2; i++){
if (data[i] != (uint32_t) -1) {
goto not_empty;
}
}
for (i = i << 2; i < bytes_to_read; i++) {
if (*(((uint8_t *) data) + i) != (uint8_t) -1) {
goto not_empty;
}
}
...
On Fri, May 26, 2017 at 11:09 AM, Jacob Rosenthal <[email protected]>
wrote:
> Just trying to cargo cult what chris said. whats appropriate? uint32_t?
>
> Could be related, but what Im seeing is
>
> data after flash_area_read before erase
>
> (gdb) p data
> $1 = {3735928559 <repeats 30 times>, 126616, 46299, 1, 45733, 1, 145408,
> 112640, 112640, 128076, 103483, 1, 127960, 536872908, 43465, 4294967295,
> 4294967295, 4294967295,
> 4294967295, 1, 536872908, 4294967295, 43503, 1, 127960, 127948,
> 536872908, 127960, 536872963, 112640, 536872960, 46289, 109467, 103572,
> 16777728}
> (gdb) p data
> $2 = {2532554812, 36, 32, 860, 18, 0, 0, 0, 536887296, 145449, 4085258752,
> 4085286932, 553879568, 1744979993, 1610760970, 1744979992, 3735928559
> <repeats 14 times>, 126616,
> 46299, 1, 45733, 1, 145408, 112640, 112640, 128076, 103483, 1, 127960,
> 536872908, 43465, 4294967295, 4294967295, 4294967295, 4294967295, 1,
> 536872908, 4294967295, 43503, 1,
> 127960, 127948, 536872908, 127960, 536872963, 112640, 536872960, 46289,
> 109467, 103576, 1090519552}
>
>
> data after flash_area_read after erase
>
>
> $2 = {4294967295 <repeats 16 times>, 536874064, 536874068, 536883092,
> 536873880, 0, 38233, 536883088, 536874048, 536874048, 536873534, 536876440,
> 111639, 2, 536874048, 126612,
> 46299, 1, 45733, 1, 145408, 112640, 112640, 126612, 46299, 32, 45733, 32,
> 145408, 32, 0, 536873624, 103483, 32, 0, 536873688, 108847, 1, 127956,
> 536883076, 536878212,
> 127956, 536873687, 2, 127968, 46289, 109155, 103576, 1090519552}
> (gdb)
>
> seems like it successfully erases only 16 uint32s
>
>
> On Thu, May 25, 2017 at 11:49 PM, Simon Ratner <[email protected]> wrote:
>
> > At a glance, you are confusing bytes with ints (data is declared as
> > unsigned int), so for the most part you are comparing uninitialised stack
> > memory.
> >
> > Hth,
> >
> > simon
> >
> > On Thu, May 25, 2017 at 11:04 PM, Jacob Rosenthal <
> [email protected]
> > >
> > wrote:
> >
> > > Pushed something like you described, new flash_area_is_empty function
> in
> > > flash_map
> > > https://github.com/apache/incubator-mynewt-core/pull/281
> > >
> > > Currently doesnt actually work.. either my code sucks or the erase
> doesnt
> > > actually ever succeed on nrf51 is is leaving behind non 0xff bytes..
> not
> > > sure which
> > >
> > > On Tue, May 16, 2017 at 5:26 PM, Christopher Collins <[email protected]
> >
> > > wrote:
> > >
> > > > On Tue, May 16, 2017 at 05:11:36PM -0700, Jacob Rosenthal wrote:
> > > > > Seems like it could go in flash_map?
> > > > >
> > > > > Its also been requested to also have a function that detects if an
> > area
> > > > > should be erased, based on it having any non 0xff bytes within.
> > > > >
> > > > > Should that go there as well.
> > > >
> > > > That is the same thing, isn't it?
> > > >
> > > > > Whats a good method to loop through all bytes of a flash area?
> > > >
> > > > Perhaps something like the following:
> > > >
> > > > 1. Allocate a buffer that is properly aligned to be accessed by an
> > > > unsigned int*. It may take some testing to
> > > > determine a good size that balances speed and size efficiency; I
> would
> > > > start with 64 bytes. I would also start by putting this buffer on
> the
> > > > stack.
> > > >
> > > > 2. Read a chunk of flash into the buffer
> > > > (min(size-of-buffer, num-unread-bytes).
> > > >
> > > > 3. Use an unsigned int* to iterate through the buffer. If the
> pointer
> > > > points to something other than (unsigned int)-1, then the flash is
> not
> > > > erased.
> > > >
> > > > 4. If there are any remaining bytes (i.e., number of bytes read is
> not
> > a
> > > > multiple of sizeof(unsigned int)), compare them individually against
> > > > 0xff using a uint8_t*.
> > > >
> > > > Chris
> > > >
> > >
> >
>
