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Rock Pi 4C variant adds mini-DP while Rock Pi E offers dual LAN

Oct 2, 2019 — by Eric Brown 7,402 views

[Updated: Oct. 3] — Radxa is prepping a $75 “Rock Pi 4C” variant of the RK3399-based Rock Pi 4B SBC that adds a 2-lane mini-DisplayPort for dual simultaneous displays. There’s also an RK3328-based “Rock Pi E” in the works with dual LAN ports.

Radxa CEO Tom Cubie announced an upcoming “Rock Pi 4C” SBC that adds dual simultaneous display support to the Rock Pi 4B design. There’s also a tiny Rock Pi E SBC in the works, which we updated on Oct. 3 (see farther below).

The Rock Pi 4C, which will ship by the end of the month at $74.95, is a variant of the similarly open-spec Rock Pi 4, a Rockchip RK3399 based Raspberry Pi pseudo-clone. More specifically, it’s based on the Rock Pi 4B, a $74.95 model with 4GB RAM and a WiFi/Bluetooth module. There’s also a $39 4A model with 1GB RAM and no wireless. Both of these Linux- and Android-driven boards were updated to v.1.4 in late June with the addition of 4MB SPI for booting NVMe drives, among other enhancements.

Rock Pi 4C (left) and earlier Rock Pi 4B
(click images to enlarge)

The Rock Pi 4C enables dual display support by adding a mini-DisplayPort. To make room, Radxa switched the full-size HDMI 2.0 port to a micro-HDMI port. The mini-DP is enabled via the hexa-core RK3399 SoC’s USB Type-C controller, which supports DP output in Alt mode, shared with USB 3.0 buses.


Because Radxa used the Type-C controller to drive dual USB 3.0 host ports instead of a Type-C port, the mini-DP only has 2-lanes instead of 4-lanes. (As before, there’s also a USB Type-C port limited to power input.)

Cubie had expected the 2-lane limitation would reduce DP resolution to 1080p HD, but as it turned out, the port can drive 2560 x 1440 @ 60Hz displays on a DP 1.2 monitor. The micro-HDMI can continue to power 3840 x 2160 @ 60Hz displays when the mini-DP is not in use, and in dual simultaneous display mode each port can achieve 2560 x 1440 @ 60Hz in extend mode.

Presumably the 2-lane MIPI-DSI interface is still available, but Cubie did not mention whether you can perform dual displays with DSI and either DP or HDMI. Previously, the DSI specs listed support for “dual display mirror or extend with HDMI,” but apparently only at HD resolution.

Like the 4B model, the 4C is offered only with 4GB LPDDR4. For the 4C model, Radxa switched to “a new 64-bit single chip” RAM module “for better manufacturing and QA,” writes Cubie.

Otherwise, the Rock Pi 4C is identical to the 4B, which closely matches the Raspberry Pi layout and feature set. It’s equipped with a native GbE port with PoE support via the Rock Pi Poe HAT introduced in June. In addition to the 2x USB 3.0 ports, there are two USB 2.0 ports.

Other features include MIPI-CSI, an audio jack with mic, an RTC, and 40-pin GPIO. The Rock Pi 4 A and B have an 0 to 80°C range, a 5.5-20V input, and support for Android 9.0. Debian, and Ubuntu Server.

Cubie announced the 4C today via email and at the Foundation’s XDC2019 conference in Montréal. This open source graphics conference covers topics including the Linux kernel, Mesa, DRM, Wayland, X11, and Panfrost. Cubie noted his particular interest in Panfrost, the open source Mali GPU driver project. Radxa has posted a YouTube demo showing Panfrost running on the Rock Pi 4’s RK3399 SoC, which includes a high-end Mali-T864 GPU in addition to 2x Cortex-A72 @ up to 1.8GHz and 4x Cortex-A53 @ 1.4GHz.

Rock Pi E

On the Radxa site we noticed a preliminary page with no photo for an upcoming Rock Pi E SBC that features dual Ethernet ports. The Rock Pi E runs Debian based on Rockchip’s Linux 4.4 kernel on the Rockchip RK3328, a quad-core, Cortex-A53 SoC clocked here at up to 1.3GHz. The RK3328 is also found on Pine64’s Rock64.

Like the RK3308 based Rock Pi S SBC announced in June, the Rock Pi E has a tiny footprint — 65 x 56mm compared to the 43 x 43mm Rock Pi S. After initially posting this story we were alerted to a secondary wiki page that lists both GbE and 10/100 Fast Ethernets with optional PoE.

The Rock Pi E supports 512MB to 4GB DDR3 and offers a microSD slot and between 16GB and 128GB eMMC. There’s also a USB 3.0 host port and an 802.11n/BT 4.0 wireless module. Like the Rock Pi S, this appears to be a headless board without display interfaces.

Other features include a 40-pin GPIO header and USB Type-C port with 5V input. You also get an RTC connector, LEDs, and internal single USB 2.0, I2S0, 4x I2C, 2x SPI, 3x UART, 3x PWM, and 2x 5V and 3.3V interfaces.

Rock Pi S

Since our June report on the Rock Pi S, the SBC has become available at Radxa distributors including Allnet China, starting at $10 with 256MB RAM, ranging up to $24 with 512MB RAM, a wireless module, PoE, and 1GB NAND.

The Rock Pi S runs Debian on the RK3308, which has 4x low-power, 64-bit Cortex-A35 cores but no 2D or 3D GPU. The SBC does, however, offer extensive digital audio interfaces via a 26-pin header. Other features include USB 2.0 host OTG Type-C ports, 10/100 Ethernet, and a second 26-pin header for GPIO.

Rock Pi X

Last month, Radxa unveiled its first x86-based SBC. The Rock Pi X runs Linux or Windows 10 on an Intel “Cherry Trail” Atom x5-Z8300 with up to 4GB LPDDR3 and up to 128GB eMMC. The open-spec Raspberry Pi lookalike is further equipped with USB 3.0, microSD, HDMI, eDP/MIPI, GbE, and a 40-pin header plus optional WiFi and Bluetooth 4.2 LE.

Further information

The Rock Pi 4C will be available for $74.95 later this month. No documentation appears to have been posted. No shipping or pricing information was provided for the upcoming Rock Pi E. More information may be found on the preliminary Rock Pi E product page and the newly discovered wiki and getting started page.

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One response to “Rock Pi 4C variant adds mini-DP while Rock Pi E offers dual LAN”

  1. Bernard says:

    Why does there need to be a 2 lanes limitation on the mini-DP port?

    According to:
    This states that the chip has a single DisplayPort controller that needs to be shared by both Type-C controller, but that the Type-C PHY does support 4 lanes operation.

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