B-M2MEM-PACK1 shield

Overview

The ST B-M2MEM-PACK1 M.2 serial memory pack carries two devices: a serial NOR flash and an I2C EEPROM that describes the module. This sample reads the EEPROM, prints what the module claims to be, and then runs three tests on the flash to check that the claim holds and that the memory is usable.

The tests are:

Compare JEDEC IDs. Read the JEDEC ID from the flash at runtime and compare it with the value the identification EEPROM reports for the memory position. A mismatch means the module is not what its EEPROM says it is.
Erase. Erase one sector and check that the operation succeeds. The remaining test depends on this one, so the sample stops if it fails.
Write and read back. Write a known pattern into the erased sector and read it back.

The first test needs the jedec-id property on the flash node. Shield variants that do not carry it skip that test and run the other two.

Results go to the console and to the two shield LEDs, so the sample is also usable without a serial terminal:

LED behaviour	Meaning
Alternating blink	A test is about to start
Green for 2 s	The test passed
Red for 2 s	The test failed
Both steady on	All tests completed

Requirements

A board with an M.2 Key A slot wired according to the ST serial memory connector pinout (see UM3611), exposing the m2mem_connector node and the labels listed in the ST B-M2MEM-PACK1 M.2 serial memory pack shield documentation, with a B-M2MEM-PACK1 module fitted. The tests write to the flash at offset 0xff000, so any data stored there is lost.

Building and Running

This example uses a Nucleo U3C5ZI Q board. Select the shield variant that matches the fitted module:

west build -b nucleo_u3c5zi_q --shield b_m2mem_pack1_mb1928_33lb samples/shields/b_m2mem_pack1
west flash

The other variants are b_m2mem_pack1_mb1927_18ba, b_m2mem_pack1_mb1927_33ba and b_m2mem_pack1_mb1928_33la.

Sample Output

The board information read from the EEPROM is printed first, followed by one section per test:

==============================================
 B-M2MEM-PACK1 shield test
==============================================
ID EEPROM size: 16384 bytes
Board: nucleo_u3c5zi_q

EEPROM board information
----------------------------------------------
Card part number:           MB1928-33LB-C01
...

----------------------------------------------
TEST 1: Compare JEDEC ID's:
----------------------------------------------
JEDEC ID - devicetree:       ef 40 15
JEDEC ID - eeprom:           ef 70 15
jedec id stored in eeprom doesn't match one in devicetree.
TEST 1: FAIL
----------------------------------------------

----------------------------------------------
TEST 2: Erase flash section and verify erased:
----------------------------------------------
flash_erase success.
TEST 2: PASS
----------------------------------------------

----------------------------------------------
TEST 3: Write flash section and verify written:
----------------------------------------------
Data written matches data read.
TEST 3: PASS
----------------------------------------------

==============================================
 All tests completed: 2/3 passed
==============================================

Known result on MB1928-33LB

The run shown above is the expected one for this module. Its EEPROM records the JEDEC ID ef 70 15, but the fitted W25Q16JV answers ef 40 15. The second byte is the memory type and separates two ordering options of the same part: 40 is the plain SPI variant that is actually fitted, 70 is the DTR one.

The devicetree value is the correct one, and it is verified on every boot: the flash driver reads the JEDEC ID and compares it against the jedec-id property before switching to quad mode, so the device would not become ready if they disagreed.

The error is in the reference EEPROM record published by ST, not in a single mis-programmed module, so TEST 1 is left strict. It reports a real inconsistency, and the two flash tests still run and pass.