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SPI data flash device drivers (pure Python)

Project description

SPI data flash device drivers (pure Python)

SPI flash devices, also known as DataFlash are commonly found in embedded products, to store firmware, microcode or configuration parameters.

PySpiFlash comes with several pure Python drivers for those flash devices, that demonstrate use of SPI devices with PyFtdi. It could also be useful to dump flash contents or recover from a bricked devices.

Supported SPI flash devices

Vendor Atmel Atmel Macronix SST Winbond Eon Numonix Micron
DataFlash AT45 AT25 MX25L SST25 W25Q EN25Q M25P N25Q
Status Tested Tested Tested Tested Tested Not tested Not tested Tested
Sizes (MiB) 2,4 2,4,8 2,4,8,16 2,4 2,4     8
Read (KiB/s) 1278 1279 1329 642 1252     1315
Write (KiB/s) 56 64 71 2 63     107
Erase (KiB/s) 60 63 31 500 60     84

Notes about performances

  • Read operation is synchronous with SPI bus clock: it therefore only depends on the achievable frequency on the SPI bus, which is bound to the highest supported frequency of the flash device.
  • Write operation depends mostly on the flash device performance, whose upper limit comes mostly from the maximum write packet size of the device, as the device needs to be polled for completion after each packet: the shorter the packet, the higher traffic on the SPI and associated overhead.
  • Erase operation depends mostly on the flash device performance, whose fully depends on the flash device internal technology, as very few and short packets are exchanged over the SPI bus.

Supporting new flash devices of series ‘25’

Many flash devices support a common subset to for read/write/erase operations. Critical differences appear with lock and protection features, and with security features. An NDA is often required to obtain details about the advanced security features of these devices.

It should be nevertheless quite easy to add support for new flash device variants:

  • match method in the PyFtdi flash device API should be the first to look at to detect more compatible flash devices.

Supported SPI flash commands

The SPI device driver is automatically selected based on the detected SPI flash device
Read byte sequences of any size, starting at any location from the SPI flash device
Write arbitrary byte sequences of any size, starting at any location to the SPI flash device
Erase SPI flash device blocks, whose size depend on the capabilities of the flash device, typically 4KiB and/or 64KiB.
Unlock any protected flash device sectors

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