• Product Reviews, Single-board Computers
    6 min | 6916

    #Rock Pi S: a tinier version of the Raspberry Pi with Alexa functionalities

    Product Reviews, Single-board Computers | 6 min | 6916

    Radxy, the company behind the Rock Pi 4 is back! A couple of days ago, I've received the Rock Pi S (see Fig. 1), a miniature developer board that measures just 38 x 38 mm. The board is powered by the Rockchip RK3308 SoC, which integrates four 64-bit ARM Cortex-A35 cores (Ultra-High-Efficiency). Each of the cores reaches up to 1.3 GHz. The SoC also has a built-in voice activity detector (VAD) for use with IoT and smart voice applications.

    Despite its tiny size, the Rock Pi S includes a 26-pin GPIO header along with a 26-pin audio/voice header and a microSD card reader. Additionally, the Rock Pi S has a 100 Mbps Ethernet port, a USB 2.0 Type-A port and a USB 2.0 Type-C port that supports OTG and 5V power. You can choose between two RAM options: 256 MB or 512 MB and optionally, you can get 1-8 GB of onboard NAND for storage, and an extra RTL8723BS controller that supports Wi-Fi and Bluetooth 4.0. Speaking of OS, the board runs Debian (right now only Stretch) and supports also the Buildroot.

    The board costs between $9.99 and $23.99 depending on the features that you want. The cheapest version has only 256 MB RAM. However, most expensive version includes 512MB, Bluetooth 4.0, Wi-Fi, PoE and 1GB of onboard NAND storage (versions with 8 GB are still not available to sell).

    Since my last posts are about evaluation of hardware for IoT, I wanted to buy one board from Allnetchina to test the performance. Unfortunately, they do not ship to Germany. Thus, I contacted Radxa and they reacted quickly (thanks again to Norbert and Tom) and sent me a board to evaluate. So let's evaluate the board!

    The Rock Pi S
    Fig. 1: The Rock Pi S


    The following table includes some of the main features of the board. One of the pin headers has colors to indicate the pin functionalities (red = +V, black = GND, etc. -see Fig. 1). I find this a nice upgrade.

    Rock Pi S
    CPUSoC – Rockchip RK3308 quad-core Cortex A35 processor @1.3 GHz
    System Memory256 to 512 MB SDRAM
    Storage microSD card for OS storage media

    optional: 128 MB/1 GB onboard NAND storage for cost saving

    Connectivity10/100M Ethernet
    optional: 802.11 b/g/n WiFi 4 (RTL8723BS) with external antenna
    USB1x USB 2.0 host ports
    1x micro USB OTG type-C port
    Expansion headers26-pin Pi GPIO header
    26-pin voice/audio header
    Supported OSDebian and Buildroot
    Power Supply5V via micro USB port or optional PoE (additional HAT required)
    Dimensions - Weight38 x 38 mm - 26 g

    The hardware and software that will be used in this article are listed here:

    Installing/Compiling Debian

    You can find the official images here. Nowaday only Debian Stretch and Slackware ARM are available, but there are plans for Ubuntu Server and Armbian (Wip) -this should be there, but the link is still not working-.

    At the moment of writing this article, the Debian image (dated 2019-08-06) does not support temperature measuring. Thus, for my test with the N-Queens-Problem benchmark, I had to compile an image from scratch, because the temperature support was added with this commit on GitHub.

    You can follow the instructions from this link, but I prefer to use a Docker with the needed toolchain, libraries and packages, so I combined two tutorials together and these are the steps:

    1. Install the prerequisites and Docker:

      sudo apt-get update
      sudo apt-get install binfmt-support qemu-user-static
      curl -sSL https://get.docker.com | sh  
    2. Download the repository and switch the branch:

      cd ~
      git clone --recursive https://github.com/radxa/rockchip-bsp.git
      cd rockchip-bsp
      git checkout stable-4.4-rockpis
      git fetch origin
      git rebase origin/stable-4.4-rockpis
      git submodule update
      cd kernel
      git checkout stable-4.4-rockpis
      cd ../u-boots
      git checkout stable-4.4-rockpis
    3. Build the Docker image with the tools and libraries for compiling the image:

      cd ~/rockchip-bsp/docker
      sudo docker build -t rockchip-radxa:1 -f ./Dockerfile .

      The Docker image rockchip-radxa:1 is ready. Everytime you want to build images, just run a Docker container.

    4. Run the Docker container:

      docker run --privileged -it -v ~/rockchip-bsp:/root rockchip-radxa:1 /bin/bash

      The line starts a container from the image rockchip-radxa:1 in an iterative mode (-it), links the folder (-v) ~/rockchip-bsp with /root and defines the entrypoint to /bin/bash. Thus, after running that line, you are inside the container and the repositories are available under /root/.

    Now, after installing prerequisities and building and running the container, you can build the image with the following steps:

    cd /root/
    # Build u-boot
    ./build/mk-uboot.sh rockpis
    # Build kernel
    ./build/mk-kernel.sh rockpis

    The generated images will be copied to out/u-boot and you will get the kernel image and dtb file under out/kernel/:

    root@ae530e6ef32d:~# ls out/u-boot/
    idbloader.img  sd-nand  spi  trust.img  uboot.img
    root@ae530e6ef32d:~# ls out/kernel/
    hw_intfc.conf  Image  overlays  rockpi-s-linux.dtb

    After that, you need to build a base debian system from linaro. You can choose from a 32bit or a 64bit version:

    # Use one of this option:
        # To build 32bit rootfs:
    export ARCH=armhf   # I used this option to build the base image
        # To build 64bit rootfs:
    export ARCH=arm64   

    and then, run these lines to build the image.

    cd rootfs
    dpkg -i ubuntu-build-service/packages/*        # ignore the broken dependencies, they will be fixed in the next step
    apt-get install -f
    RELEASE=stretch TARGET=desktop ARCH=${ARCH} ./mk-base-debian.sh

    This bootstraps a Debian stretch image, and you get a rootfs tarball named linaro-stretch-alip-xxxx.tar.gz.

    If you get the following error:

    chroot: failed to run command `/usr/bin/env': Exec format error
    Failed to run livebuild, please check your network connection.

    it is probably becase you did not run this on your host computer:

    sudo apt-get install binfmt-support qemu-user-static

    Then, build the rk-debian rootfs with debug using:

    VERSION=debug ARCH=$ARCH ./mk-rootfs-stretch.sh  && ./mk-image.sh

    This installs Rockchip specified packages and hooks on the standard Debian rootfs and generates an ext4 format rootfs image at rootfs/linaro-rootfs.img.

    Finally, combine everything into one image using:

    build/mk-image.sh -c rk3308 -t system -r rootfs/linaro-rootfs.img

    This combines the u-boot, kernel and rootfs into one image and generates a GPT partition table. The output is out/system.img

    After that, you can exit the container executing the command exit.

    The last step is to flash the image on a microSD card. You can use e.g. etcher to do that. Please be aware that the default user and password to connect using SSH will be: linaro-

    Performance Test

    The N-Queens Problem library needs python3 and the tqdm module. Thus, to install those type the following:

    sudo apt-get install python3 python3-pip
    pip3 install tqdm

    Because the RockPi does not have a GPU temperature sensor (or any function that provides that information), I modified the get_gpu_temp(...) function in the temperature.py file as:

    def get_gpu_temp(self):
        #res = os.popen('vcgencmd measure_temp').readline()
        #res = float(res.replace('temp=','').replace('\'C\n',''))
        res = float(os.popen("cat /sys/class/thermal/thermal_zone1/temp").read())/1000
        return res

    to return the temperature of the thermal zone 1.

    For the test, I used the same heatsink as for the Raspberry Pi:

    E-ink Screen
    • Aluminum Heatsink Kit

    The N-queens-problem benchmark (N=12) was launched and repeated 100/50 times with multi-thread and single-thread configuration, respectively. The N-queens-problem is a well-known problem that consists of placing N chess queens on an N×N chessboard so that no two queens attack each other. In this case, there are 14200 solutions for 12 queens.

    The multi-thread and single-thread performances resulted as described in Fig. 2a and 2b, respectively.

    Fig. 2a: Multi-thread ConfigurationFig. 2b: Single-thread Configuration

    The following table sumarizes the performance of the Rock Pi S and compares it with the Orange Pi Zero LTS (Armbian) and Raspberry Pi 3B and 3B+ models (Raspbian Stretch).




    Zero LTS


    Model 3B+


    Model 3B

    Avg. Multi-Thread Solving Time112.32 s69.97 s62.66 s70.85 s
    Multi-Thread Max. Temperature56.16 °C71.75 °C68.78 °C78.69 °C
    Avg. Single-Thread Solving Time336.14 s251.65 s213.34 s251.30 s
    Single-Thread Max. Temperature48.19 °C31.10 °C54.22 °C52.61 °C

    The performance is very limited, but I think it is a problem of the Kernel/OS. The maximal temperature is very low for the chip, thus I estimate that the performance is somehow limited by software. I'll keep you updated when the new images are released. The single-thread test was in average 3.00x slower than the multi-thread test (274.77 min vs 91.85 min to solve 50 N-queens-problems).


    The market has become more difficult for competitors with the release of the Raspberry Pi 4. But, it is still worth thinking about alternatives to Raspberry in the low-cost segment. The Rock Pi S positions itself here against the much lower-power, single-core variants of the Raspberry Pi Zero. In comparsion with the Orange-Pi Zero LTS, the performance is still very limited. But as I said, it has to be a problem with the OS/Kernel. The board is very small and the pin header with colors is a great idea. The community has to grow up and the documentation is still in its beginning phase, which makes it difficult to experiment with the board. However, the audio/voice capabilities of the RK3308 can make a big difference in decision making to buy such a board. Thus, I will try in the next days to use the 26-pin audio/voice header, and see how it works. Stay tuned!


    Stuart Naylor 08.17.2020


    rock@rockpis:~/RPi3-64-Bit-Benchmarks$ ./whetstonePi64
    Single Precision C Whetstone Benchmark armv8 64 Bit, Mon Aug 17 08:46:47 2020
           0.04 Seconds          1   Passes (x 100)
           0.06 Seconds          5   Passes (x 100)
           0.21 Seconds         25   Passes (x 100)
           1.06 Seconds        125   Passes (x 100)
           5.28 Seconds        625   Passes (x 100)
    Use 1182  passes (x 100)
    From File /proc/cpuinfo
    processor       : 0
    BogoMIPS        : 48.00
    Features        : fp asimd aes pmull sha1 sha2 crc32
    CPU implementer : 0x41
    CPU architecture: 8
    CPU variant     : 0x0
    CPU part        : 0xd04
    CPU revision    : 2
    processor       : 1
    BogoMIPS        : 48.00
    Features        : fp asimd aes pmull sha1 sha2 crc32
    CPU implementer : 0x41
    CPU architecture: 8
    CPU variant     : 0x0
    CPU part        : 0xd04
    CPU revision    : 2
    processor       : 2
    BogoMIPS        : 48.00
    Features        : fp asimd aes pmull sha1 sha2 crc32
    CPU implementer : 0x41
    CPU architecture: 8
    CPU variant     : 0x0
    CPU part        : 0xd04
    CPU revision    : 2
    processor       : 3
    BogoMIPS        : 48.00
    Features        : fp asimd aes pmull sha1 sha2 crc32
    CPU implementer : 0x41
    CPU architecture: 8
    CPU variant     : 0x0
    CPU part        : 0xd04
    CPU revision    : 2
    Serial          : 2f2aeacee81f7ce9
    From File /proc/version
    Linux version 4.4.143-55-rockchip-g6b7accbc999b (root@431768422ca2) (gcc version 7.3.1 20180425 [linaro-7.3-2018.05 revision d29120a424ecfbc167ef90065c0eeb7f91977701] (Linaro GCC 7.3-2018.05) ) #1 SMP PREEMPT Wed Jul 29 02:54:35 UTC 2020
              Single Precision C/C++ Whetstone Benchmark
    Loop content                  Result              MFLOPS      MOPS   Seconds
    N1 floating point     -1.12475013732910156       362.994              0.063
    N2 floating point     -1.12274742126464844       379.590              0.419
    N3 if then else        1.00000000000000000               256559280.000    0.000
    N4 fixed point        12.00000000000000000                1616.227    0.230
    N5 sin,cos etc.        0.49911010265350342                  24.615    3.995
    N6 floating point      0.99999982118606567       310.430              2.054
    N7 assignments         3.00000000000000000                 776.080    0.281
    N8 exp,sqrt etc.       0.75110864639282227                  14.909    2.949
    MWIPS                                           1183.046              9.991