# NTAG5Link Config Verification via NFC Reader

**Date**: 2026-03-03
**Status**: Partial — tag detected, config read requires ACR1552

## Goal

Read-only verification that the NTAG5Link Click board's configuration matches xblink requirements.

## Tool

`tools/ntag5_config_check.py` — Python script using pyscard (PCSC) with auto-detection of reader capabilities.

**Reader support:**
- **ACR1552**: Full NXP config verification via transparent ISO15693 mode (NXP READ_CONFIG 0xC0)
- **uFR Zero (CCID)**: Basic tag info only — UID, EEPROM blocks. Cannot read NXP config registers.

## 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 |

## uFR Zero Investigation Results

The D-Logic uFR Zero Multi-ISO reader presents as a **CCID** (USB SmartCard class 0x0B) device, not serial.

**USB**: VID:PID `3629:301b`, serial "UD101156"

### What works (PCSC/CCID)

| Command | APDU | Result |
|---------|------|--------|
| GET_DATA (UID) | `FF CA 00 00 00` | UID: `E0:04:01:58:7F:8F:11:00` (NXP ISO15693) |
| READ_BINARY | `FF B0 00 xx 00` | Reads ISO15693 user EEPROM blocks |
| NDEF CC (block 0) | `FF B0 00 00 00` | `E1 40 80 09` — NDEF v4.0, 1024 bytes |

### What doesn't work

| Approach | Result | Why |
|----------|--------|-----|
| uFCoder `ReaderOpen` | 0x1002 (timeout) | Library scans serial/tty, doesn't support CCID USB |
| uFCoder `ReaderOpenHnd_ZeroUSB` | 0x0054 (opening error) | Even with pcscd stopped |
| PCSC transparent (FF C2) | SW=6A81 | Not supported by uFR Zero CCID firmware |
| CCID escape (IOCTL 0x42000001) | 6A81 for all commands | Advertised but non-functional |
| Raw ISO15693 via SCardControl | 6A81 | No passthrough mechanism |

### Key finding: CP210x is NOT the uFR Zero

`/dev/ttyUSB0` (`10c4:ea60`, Silicon Labs CP210x) is a **separate device** (Proxmark3). The uFR Zero is a pure CCID device with no serial interface.

### CCID setup required

The uFR Zero must be added to the CCID driver's device list:

1. Add VID `0x3629` / PID `0x301B` to `/usr/lib/pcsc/drivers/ifd-ccid.bundle/Contents/Info.plist`
2. Set `ifdDriverOptions` to `0x0001` (enables CCID exchange — though escape commands still return 6A81)
3. Restart pcscd: `systemctl restart pcscd`

## Path Forward: ACR1552

The ACR1552 reader supports transparent ISO15693 mode (FF C2 pseudo-APDUs with TLV encoding), enabling NXP custom commands. The `ntag5_config_check.py` tool auto-detects the ACR1552 and switches to full config verification mode.

```python
# ntag5sensor has proven ACR1552 + NXP custom command support:
chip = NTAG5Link(reader)
config = chip.get_config_info()
eh_config = chip.get_eh_ed_config_info()
```

## Config Change Plan (if mismatches found)

Use ntag5sensor's write functions via ACR1552:

```python
# 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)
```