I'm sorry about my impoliteness earlier. What you said reminded me of my 
experience reporting issues with Docker, where there were issues that the very 
opinionated devs refused to do anything about. That and other bad experiences 
also made me hesitant to reach out. I intend to submit a couple patches soon, 
one to support Zetta NOR flash devices, and one for adding helpful information 
to the error message.


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**[tickets:#408] No support for generic SPI flash**

**Status:** new
**Milestone:** 0.11.0
**Created:** Sat Jul 08, 2023 06:33 AM UTC by Ben Larson
**Last Updated:** Wed Jul 12, 2023 09:57 AM UTC
**Owner:** nobody


I have been using the RP2040 with an SPI flash chip that was not on the list in 
`src/flash/nor/spi.c`. I found that I could write programs onto the chip using 
the RP2040 bootloader (which presents itself as a USB mass storage device), but 
OpenOCD 0.12.0 was unable to upload anything to the flash, giving the error 
`Unknown flash device (ID 0x001560ba)`. Considering that almost all SPI flash 
chips can be programmed and read using the same commands and parameters, 
shouldn't an unknown flash device be treated that way, as done in the RP2040 
bootloader?

(sourced from multiple datasheets and Pico bootrom code at 
[https://github.com/raspberrypi/pico-bootrom/tree/master/bootrom])
* use a slow clock speed
* keep ~WP pin high
* 03h reads until stopped
* 06h enables writing
* 20h erases 4kB (usually called a sector)
* 02h writes up to 256B (usually called a page)
* assume that the chip has enough memory when writing, then verify by reading

Am I missing anything? While reading/writing/erasing past the end of the flash 
memory seems to be undefined behavior, it seems very unlikely to damage the 
chip, and should always result in write verification failure.


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