xblink/docs/plans/2026-03-03-ntag5-config-check.md

NTAG5Link Config Verification via uFR Zero

Date: 2026-03-03 Status: Tool written, reader connection blocked

Goal

Read-only verification that the NTAG5Link Click board's configuration matches xblink requirements, using the Digital Logic uFR Zero Multi-ISO reader.

Tool

tools/ntag5_config_check.py — Python script using uFCoder library (ctypes) in ISO15693 transparent mode.

Features:

• ISO15693 INVENTORY to discover all tags by UID
• Addressed mode for all config reads (supports multiple tags in field)
• Reads CONFIG block (0x37) and EH/ED CONFIG block (0x3D)
• NXP system info for interface type verification
• Checks against xblink expected config values

Expected Config

Setting	Expected	Config Location
EH mode	low_field_strength	CONFIG byte 0, bits 3:2 = 10
Use case	i2c_slave	CONFIG byte 1, bits 5:4 = 00
SRAM enabled	true	CONFIG byte 1, bit 1 = 1
Arbiter mode	sram_passthrough	CONFIG byte 1, bits 3:2 = 10
EH enable	true	EH_CONFIG byte 0, bit 0 = 1
EH voltage	3.0V	EH_CONFIG byte 0, bits 2:1 = 10

Reader Connection Issue

Problem: uFCoder library returns UFR_TIMEOUT_ERR (0x1002) for all ReaderOpenEx parameter combinations.

USB device: 10c4:ea60 — Silicon Labs CP2102 USB to UART Bridge Controller, iSerial "0001". Generic descriptor, no D-Logic branding in USB strings.

Raw serial investigation:

• At 1 Mbps (expected uFR baud): responds with 00 80 (2 bytes) — not a valid uFR protocol frame (expected 6+ bytes with 0x55...0xAA framing)
• At 115200 bps: returns ASCII shell commands mentioning "systemctl", "proxmark3" paths
• At 250 Kbps: returns structured but unrecognized data

Possible causes:

1. Device may not be a uFR Zero — the CP210x bridge has generic descriptors
2. Reader firmware may need updating
3. Reader may be in a non-standard mode
4. Different hardware variant requiring different protocol

Next steps:

1. Physically verify the device is indeed the uFR Zero (check labels, LEDs)
2. Try the D-Logic ufr_online Windows utility to confirm reader identity
3. If confirmed as uFR Zero, check firmware version and update if needed
4. Alternative: use the ACR1552 PCSC reader with ntag5sensor directly (requires porting the reader to share the field with NTAG5 Click)

Fallback Plan: ntag5sensor + ACR1552

If the uFR Zero connection cannot be resolved, use the existing ntag5sensor Python tooling with the ACR1552 PCSC reader:

# From ntag5sensor — already has full config read/write support
chip = NTAG5Link(reader)
config = chip.get_config_info()
eh_config = chip.get_eh_ed_config_info()

The ACR1552 is already proven with ntag5sensor. Only change needed: physically position the ACR1552 over the NTAG5 Click board instead of the uFR Zero.

Config Change Plan (if mismatches found)

Use ntag5sensor's write functions (via ACR1552 or adapted for uFR Zero):

# Set I2C slave mode + SRAM passthrough + SRAM enable
chip.write_config1(
    sram_enable=True,
    arbiter_mode=NXP_CONFIG_1_ARBITER_MODE_SRAM_PASSTHROUGH,
    use_case=NXP_CONFIG_1_USE_CASE_CONF_I2C_SLAVE
)

# Set EH: 3.0V, enabled, current limit TBD
chip.write_eh_ed_config(
    enable=True,
    voltage=NXP_EH_CONFIG_EH_VOUT_V_SEL_3_0,
    current=NXP_EH_CONFIG_EH_VOUT_I_SEL_12_5,  # max for testing
    ed_config=NXP_ED_CONFIG_NFC_FIELD_DETECT
)

# Set EH mode in CONFIG byte 0
chip.write_config0(eh_mode=NXP_CONFIG_0_EH_MODE_LOW_FIELD_STRENGTH)