P2U52 Adapter EC25‑E FAQ – UAC Audio, VoLTE, Firmware, SIM Slot

FAQs: P2U52 Adapter with EC25-E Mini PCIe

Product Overview

The P2U52 Adapter is an industrial-grade Mini PCIe to USB adapter designed to host Quectel EC25-E Mini PCIe modules. It converts USB 5V input to 3.6V via a DC-DC power chip to power the module and SIM card.
Notes
NOTE: This is a pure hardware adapter — no driver is needed for the adapter itself, but the module requires its own drivers to function

Q1: What SIM card size does the push slot accept?

Answer: The push-type SIM slot accepts a Standard SIM (also known as Mini SIM, 2FF).
SIM Type
Size (mm)
Compatibility
Standard (2FF)
25 × 15 mm
✅ Direct fit
Micro (3FF)
15 × 12 mm
Requires adapter
Nano (4FF)
12.3 × 8.8 mm
Requires adapter
Notes
Recommendation: If you have a Nano or Micro SIM, please use a SIM card adapter to convert it to Standard (2FF) size before inserting

Q2: Does the EC25-E module support VoLTE?

Answer: Yes, the EC25-E module supports VoLTE functionality.

Important Considerations:

  1. VoLTE support depends on the firmware version installed on the module.
  2. Carrier certification varies by region and network operator.
  3. For European networks (including Deutsche Telekom), the EC25-EUX variant is the recommended choice as it holds specific carrier certifications for EMEA operators
AT Command
Remark
AT+QGMR
# Check firmware version
AT+QMBNCFG="list"
# List available operator profiles

Q3: Does the EC25-E module support USB Audio (UAC) for voice calls?

Answer: Yes — but UAC support is firmware-dependent.

How It Works:

The module can be configured to expose itself as a USB sound card (UAC device) to the host system. However:
  1. Older firmware may not support UAC at all.
  2. Newer firmware (e.g., EC25EFAR06A21M4G and later) includes UAC support.

Required AT Commands (Community‑validated):

AT Commands
Remark
AT+QCFG="usbcfg",0x2C7C,0x0125,1,1,1,1,1,0,1
Enables UAC function in the USB configuration.
AT+QPCMV=1,2
Routes voice data to the UAC interface.

Important Notes:

  1. The UAC interface operates at 8kHz / S16 / mono.
  2. If AT+QCFG="usbcfg" returns ERROR, the firmware does not support UAC.
  3. UAC support is firmware‑dependent. Older firmware versions may lack UAC functionality.
  4. Known firmware versions with confirmed UAC support include: EC25EFAR06A21M4G, EC25EUXGAR08A19M1G (and later)

Post‑configuration Verification:

cat /proc/asound/cards
aplay -l

Q4: Can I request a specific firmware version before shipping?

Answer: We can flash specific firmware for individual orders before shipping. By default, all modules ship with the manufacturer's standard factory firmware.