pyspiflash

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

Identification

The SPI device driver is automatically selected based on the detected SPI flash device

Read

Read byte sequences of any size, starting at any location from the SPI flash device

Write

Write arbitrary byte sequences of any size, starting at any location to the SPI flash device

Erase

Erase SPI flash device blocks, whose size depend on the capabilities of the flash device, typically 4KiB and/or 64KiB.

Unlock

Unlock any protected flash device sectors

Dependencies

PySpiFlash relies on PyFtdi module to access the SPI flash device. The internal API of PyFtdi has been changed with version 0.11.0.

PySpiFlash version	PyFtdi version
0.2.*	0.9 .. 0.10
0.3.*	0.11+