[RTL8735B / AmebaPro2] Technical Inquiry: Built-in Fast Ethernet PHY (FEPHY) Bring-up, Hardware Schematics, and SDK Configuration

Hardware
1

We are conducting a detailed feasibility and hardware evaluation for using the built-in Fast Ethernet PHY (FEPHY) on the RTL8735B (AmebaPro2) for an upcoming mass-production project.

To help us determine whether the internal FEPHY is the right path compared to an external USB-to-Ethernet bridge, we have compiled the following technical inquiries regarding silicon readiness, hardware design, and driver stability:

1. Silicon Validation & Production Readiness

  • [Q1 / A-1] Silicon Validation & Errata: Has the built-in FEPHY in RTL8735B fully passed silicon validation and reliability testing for mass production? Are there any known silicon-level errata or silicon revision limitations?

  • [Q2 / A-4] Official Recommendation & Forum Clarification: In forum thread /t/rtl8735b-fast-ethernet-interface-is-fully-functional-or-not/4794, the inquiry regarding silicon validation went unanswered, and the response suggested using USB Ethernet instead. What is Realtek’s official position—is internal FEPHY recommended for mass production?

  • [Q3 / A-8] Mass Production Reference Cases: Are there existing mass-production products or customer reference designs currently shipping with the RTL8735B internal FEPHY active?

2. Hardware Reference Design & EVB Layout

  • [Q4 / A-2] FEPHY Reference Schematics & Layout Guidelines: Please provide reference schematics and layout guidelines for FEPHY. Specifically:

    • Recommended RJ45 and network magnetics/transformer specifications.

    • Is the PHY voltage-mode or current-mode? Does the transformer center tap require an active DC bias voltage or just decoupling capacitors?

    • Differential pair trace impedance (100 Ohm) and ESD protection recommendations.

  • [Q5 / A-3] Pro2 EVB Component Omission: Why are the RJ45 jack and magnetics unpopulated (DNP) on the official AmebaPro2 EVB? Was this due to bill-of-materials (BOM) cost savings or hardware/functional limitations?

3. Software Architecture, Workarounds & Driver Stability

  • [Q6 / A-5] FEPHY Software Patch Root Cause: In component/ethernet_mii/ethernet_mii.c, there is a periodic 10-second polling thread running eth_phy_state_detect() with the comment "Pro2 FEPHY s/w patch". What specific issue or HW behavior does this software patch mitigate? Is it a workaround for link-drop or register auto-negotiation stability?

  • [Q7 / A-6] MAC Address Provisioning: Can the Ethernet MAC address be stored directly in the SoC’s internal eFuse/OTP or Flash? What is the recommended factory mass-production programming toolchain and flow for burning MAC addresses?

  • [Q8 / A-9] USB CDC-ECM Binary & Driver Bug Status:

    • Is the source code for usbh_cdc_ecm_hal.c available, or is it strictly provided as a pre-compiled library?

    • Has the issue reported in forum thread /t/amb82-mini-usb-ethernet-failing/4803 (Lwip link down $\rightarrow$ USB_DeInit during sustained RTSP streaming) been resolved in the current SDK release?

4. Power Consumption

  • [Q9 / A-7] FEPHY Power Consumption Data: What is the typical and maximum power consumption (mA / mW) of the internal FEPHY during 100Mbps TX/RX operational states? We require this data for PoE Class classification and thermal budget evaluation.

We would greatly appreciate your detailed feedback to assist our hardware architecture freeze and design review.

2

Hi @Hsu_Shawn ,

To ensure you get the most out of the Ameba AIoT ecosystem and to help us provide the best support, we would love to learn a bit more about your project and company, would you mind to fill up this Private User Form for us?

Thank you.

3

Hi Kevin,

I have filled it up already. Can someone help to answer to question?
Thank you!

4

Hi @Hsu_Shawn ,

Thanks for the update. Please give us some time to discuss internally and we will get back to you privately via email.

Thank you.