microReticulumTbeam/exercises/19_SD_Card_diag

Exercise 19: SD Card Diagnostics

This exercise exists to develop and test a reusable SD card diagnostics library, sdcard_diag, under a simple sketch that prints the current card status to the serial console.

The immediate goal is operational: when a board in the field has an SD-related problem, the serial output from this exercise should help identify which card was installed and what the board could read from it at the time of the problem.

What It Reports

The sketch prints:

• PMU and SD rail status
• SD pin map and pin levels
• SPI idle probe results for HSPI and FSPI
• Mount result and working SPI bus/frequency
• Card type and capacity
• Filesystem total, used, and free space
• Root directory summary and a few sample entries
• CID-derived identity fields:
  • mid
  • manufacturer_guess
  • oem
  • product
  • revision
  • serial
  • date
  • CID raw

Important Certainty Boundary

The following fields are read from the card and should be treated as authoritative:

• mid
• oem
• product
• revision
• serial
• date
• CID raw

The manufacturer_guess field is not authoritative. It is a best-effort interpretation of mid using community-observed mappings. This matters because:

• the public SD documentation describes the MID field, but does not provide a public authoritative MID -> vendor name table
• counterfeit or reprogrammed cards may present misleading identity data
• some real cards may use manufacturer IDs not covered by the current lookup table

Also note the difference between a retail brand and a CID-reported card identity:

• the label printed on the card or the Amazon listing may identify a reseller, storefront brand, or private-label marketer
• the CID fields identify what the card itself reports electronically
• those two may match, but they do not have to match
• for troubleshooting, trust the printed CID: line and CID raw: more than marketplace branding

For issue work, always keep the full CID: line and the CID raw: line.

Typical Output

CID: mid=0x03 manufacturer_guess=SanDisk oem=SD product=SD32G revision=8.5 serial=0x2CC7ADB4 date=2025-12
CID raw: 03 53 44 53 44 33 32 47 85 2C C7 AD B4 01 9C 6B

That output usually tells you much more than a retail package label. Even if manufacturer_guess is Unknown, the remaining fields are still valuable for correlation.

Build

From the repository root:

source /home/jlpoole/rnsenv/bin/activate
pio run -d exercises/19_SD_Card_diag/ -e cy

Upload

source /home/jlpoole/rnsenv/bin/activate
pio run -d exercises/19_SD_Card_diag/ -e cy -t upload --upload-port /dev/ttytCY

Monitor

date
source /home/jlpoole/rnsenv/bin/activate
pio device monitor -b 115200 --port /dev/ttytCY

If manufacturer_guess Is Unknown

Use the following process:

1. Capture the full CID: line and CID raw: line from the serial log.
2. Use mid, oem, and product together when searching. mid alone is often not enough.
3. Compare the card against the references below.
4. If the card still cannot be identified, record the raw CID in the issue so the lookup table in sdcard_diag can be extended later.

Suggested search terms:

SD CID MID 0xNN OID XX product YYYYY

or

microSD CID 03 53 44 53 44 33 32 47 ...

Reference URLs

These pages are useful when investigating an unknown or suspicious card.

Official SD/SD-3C references:

• SD Association Physical Layer Simplified Specification downloads page: https://www.sdcard.org/downloads/pls/
• SD Association simplified specification PDF referenced during development: https://www.sdcard.org/cms/wp-content/themes/sdcard-org/dl.php?f=Part1_Physical_Layer_Simplified_Specification_Ver6.00.pdf
• SD-3C home page: https://www.sd-3c.com/Default.aspx

Community and field-reference pages:

• IT-SD secure digital card registers: https://www.it-sd.com/articles/secure-digital-card-registers/
• Camera Memory Speed CID notes: https://www.cameramemoryspeed.com/sd-memory-card-faq/reading-sd-card-cid-serial-psn-internal-numbers/
• Zero Alpha SD technology explainer: https://zeroalpha.com.au/services/data-recovery-blog/sd/secure-digital-sd-memory-card-technology-explained

Notes For Issue Assignees

• Treat manufacturer_guess as a clue, not proof.
• Treat CID raw as evidence.
• If the board mounts the card but CID parsing fails, retain the mount and filesystem details anyway.
• If a new legitimate MID is identified, update the lookup table in lib/sdcard_diag/SdCardDiag.cpp and add provenance for the new mapping.