we are developping a imp003 new based device with a 512MB spi flash (N25Q512A13GF840E, Micron Technology Inc.).
The board was designed following the sample schemes found in the “Designing Hardware with the imp003” document, but we initially left the HOLD_L and WP_L pins unconnected (not pulled-up/down as in the sample scheme).
We assembled 3 boards and they all present the same problem. The boards behave as follows:
- when powered up the led color start flashing the “SPI Flash Error” code (long red, short amber, long off)
- during the boot no activity is present on the MISO pin of the flash
- starting a blink-up sequence stops the blinking of the led
- after the blink-up sequence ends, the flashing starts again, but signaling the “SPI Flash Not Found” error code (long amber, short red, long off)
After checking again the documentation we tried to pull-up the HOLD_L pin. We now have activity on the MISO pin during the boot sequence, but the problem persists (same blinking codes).
We also tried pulling-down the WP_L pin as shown in the sample schemes (is this really needed/correct?). This doesn’t affect the boards behavour.
To have a double check on the memory compatibility we tried replacing our 512 MB memory with the smaller 4MB one listed in the recommended components in the imp003 datasheet (MX25L4006E, Macronix). Nothing changed.
As vaguely suggested in the Micron documentation, we also tried pulling-down the clock line but without any change.
At the moment we dont have acces to a logic analyzer but we verified with an oscilloscope the flash pins activity/state and they appear to be correct. The chip supply and groung are ok. On the clock, miso and mosi pins there is activity; the HOLD_L pin is pulled-up. We also tested all the possible states of WP_L (pulled-up, pulled-down and floating).
At this point we are a little bit out of ideas. Some help/suggestions would by really appreciated.