RK3308 peripherals: USB, RMII, display and debug

Based on RK3308 Hardware Design Guide V1.0 (2018-09-14), with the 2023 V1.1 compatibility note used to identify variant boundaries. P2 Pro uses RK3308B-S; the historical reference does not replace its board design. This topic article is not a complete page-by-page translation. Source values are not ArmSoM measurements. Check actual interfaces, SDK/BSP, kernel and firmware for the board revision.

RK3308硬件设计指南_V1.0_20180914.pdf · §2.4; compatibility V1.1 §7

Check the suffix before USB design

On the original RK3308, USB0 is OTG/flashing and USB1 is host. The reference uses 2.2Ω in DP/DM and 100Ω in ID. The 2018 USB_RBIAS requirement of 133Ω 1% belongs to older silicon: the 2023 note marks C15 as NC on SMIC S, requiring the corresponding GF external resistor arrangement to change. P2 Pro uses B-S; inspect its actual schematic before judging component population rather than adding a resistor from the old drawing.

Review networking as a system

100Mbps RMII needs an external PHY. Its clock may come from a crystal or MAC_CLK; define the direction from the chosen reference. If PHY reset uses an RC circuit, the guide requires controllable PHY power. MDIO still needs a pull-up. SDIO 3.0 Wi-Fi/BT must match the SoC SDIO/UART levels, CTS/RTS direction and PCM path. Source table 2-20 labels RMII data MAC_TXD[2:0]/RXD[2:0]. Treat this as unresolved and consult PinOut/TRM rather than inventing a third RMII data wire.

Keep display and service access coherent

LCDC exposes 18 data signals; select RGB/MCU mapping from the source diagram. MCU-panel RD, WR, CS and CMD require their defined functional mapping, not arbitrary GPIO substitution. Reserve UART2_M0 when SDMMC conflicts with UART2_M1. External connectors also need series protection, ESD return paths and unpowered-state checks. Validate sustained network traffic, USB hot-plug, display refresh and audio concurrently, since isolated interface success does not prove system stability.

Source figures and review pages

Only Chinese originals are available in this batch. All four languages use the same source images, retaining figure context; image labels are not translated. Prose is editable. Page numbers are physical PDF pages.