Add support for Microchip SST26VF016B & SST26VF032B and make fastread working

[LoicGRENON]

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Pull request details

• Please check if the PR fulfills these requirements

• The commit message/s explain/s all the changes clearly
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

• Bug fix
• Added feature
• Documentation update
• Other - Please explain here: new chip support (I added it on March but I saw you added support for these chips in the meantime)

• What is the current behavior? (You can also link to an open issue here)
  Fastread mode do not work (only tested with SST26VF016B & SST26VF032B chips)

• What is the new behavior? (if this is a feature change)
  Make fastread mode works (only tested with SST26VF016B & SST26VF032B chips)

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)
  Nothing

• Other information:
  As I don't have any other chip, especially Winbond ones. Can you confirm that fastread mode is not actually working on your side ?
  If it working with other chip than Microchip ones, I probably need to do some verifications to identify it.

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[Marzogh]

Hi Loic,

Thanks for this - I'll just test this over the next day or so and pull it into the development branch. W.R.T Fast Read, the Winbond chips call for 8 dummy clocks after the 24-bit address is clocked in (Re: Section 8.2.9 in the datasheet here). I don't know if the SST25 and SST26 series need that - I'll check that out as part of the testing 🙂

[Marzogh]

Hi mate, after checking the library code, it turns out I'd made a mistake when I wrote the _beginSPI() function that broke FastRead. The bug has now been fixed (as of commit 7e0825a) and confirmed to work on both Winbond and SST26 series chips.

Also, I had already included SST26 series support in the development branch before your pull request came through, so, I won't need to merge it here after all. However, thank you for taking the time to catch and fix the bug and add support for new chips! 🙂

[LoicGRENON]

Hello,

The same fix as of commit 7e0825a is needed for SPIFram on SPIFramIO.cpp at line 164 : The dummy byte needed for fast read operation should be sent after the two-bytes address.
However, it seems to not be sufficient to make fast read to work with a FRAM chip...

[LoicGRENON]

Well, in fact the SPIFram::_read() template defined in SPIFram.h need to also be modified like SPIFlash::_read defined in SPIFlash.h

Need to change _nextByte(WRITE, FASTREAD); and _nextByte(WRITE, READDATA); to _beginSPI(FASTREAD); and _beginSPI(READDATA); at lines 339 and 342.
Then remove _transferAddress(); at line 344.

I made a new pull request that solve this new issue : #203