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ROCK Model 4C+ The last decade or so has seen the introduction of compact and affordable single-board computers, starting with the Raspberry Pi Model B and followed by numerous successors and similar products. The Radxa ROCK Model 4C+ is compatible with much of the Raspberry Pi ecosystem but adds several novel features. Single Board Computer Review by Tim Blythman T he Raspberry Pi Foundation has set the standard for single-board computers (SBCs) with many models that have appeared since the Model B in 2012. While initially intended as a computer cheap enough to be used by classrooms of students, they have found many other uses. We have reviewed a number of their models, starting with the original Model B in May 2013 (siliconchip.au/ Article/3781) and, most recently, the Model 4B in August 2019 (siliconchip. au/Article/11772). It has been around five years since the release of the Model 4B, and the Raspberry Pi Model 5 has just been released. It wasn’t easy to get one, but we are working on a review now. While waiting for the Pi 5, we decided to review this ROCK SBC as it will make an interesting comparison. You might have heard of the shamelessly named Banana Pi and Orange Pi boards. The ROCK 4C Plus from Radxa also claims compatibility with the Pi Model 4B but has some unique features that appear to set it apart from other SBCs. Altronics is selling the ROCK Model 4C+, so they sent us one to try. We have heard reports of people using single-­ board computers as desktop computers, so we included that as part of our tests. The manufacturer Radxa (https://radxa.com/about) was established in Shenzhen, China in 2012 as one of the earlier manufacturers of SBCs. Their product history includes several products that parallel those from the Raspberry Pi Foundation, including compact ‘Zero’ boards and ‘Compute’ modules. Compute modules are minimal single-board computers intended to be used in large numbers. Like many of Radxa’s single-board computers, the ROCK 4C+ uses a system on a chip (SoC) incorporating the processor, memory, peripherals, connectivity and graphics processing unit Photo 1: a small u.FL antenna (shown enlarged) is included with the ROCK 4C+ 58 Silicon Chip Australia's electronics magazine (GPU). This one is the RK3399 from the Chinese fabless semiconductor company RockChip. The RK3399 is also the main processor in several tablets and Chromebooks, as are many of RockChip’s other SoC products. Radxa’s website also mentions a commitment to opensource philosophies. Data sheets, circuit diagrams and 3D models can be found at https://wiki. radxa.com/Rock4/hardware and several software repositories are online at https://github.com/radxa The ROCK Model 4C+ The documentation for the ROCK 4C+ states that it is the same form factor as the Raspberry Pi Model 4B and is compatible with Raspberry Pi 4 accessories, so we will focus our comparisons on the Raspberry Pi 4B. Photos 2 and 3 show the front and back of the ROCK 4C+. The external connections look much the same as on the Pi 4B; the important connectors, such as USB, HDMI and Ethernet appear identically located, as do the mounting holes. Note the power button, eMMC module socket and an unpopulated SPI flash chip, none of which are present on the Pi 4B. A nice touch not seen on the various Pi models is the colour-coding of the GPIO header; the siliconchip.com.au plastic surrounding the pins is coded according to their functions. 5V pins are red, 3.3V pins are yellow and ground pins are black. The generally usable GPIO pins are green, with two special function pins being blue. It’s no substitute for a full pin map, but it could help to avoid accidental damage. Table 1 shows the main features compared to the Pi 4B. When we reviewed the Pi 4B, the 8GB RAM option was not yet available. So, in the hardware stakes, the ROCK 4C+ is similar to the Pi 4B we reviewed. The big difference is the processor; most other features are identical. Keen readers will note that the Pi 4B was specified at 1.5GHz at launch, similar to the two primary cores of the ROCK 4C+; the 1.8GHz upgrade comes courtesy of a hardware update. Differences Some interesting features are noted in the Product Brief, which can be downloaded via the User Manual link on the Altronics ROCK 4C+ product page at siliconchip.au/link/absi Page seven notes that most of the GPIO (general purpose input output) pins are rated to 3.0V nominal logic levels, with a 3.14V maximum. However, one GPIO pin is specified to work with nominal 3.3V levels (up to 3.498V). In practice, we found that the I/O pins deliver a voltage close enough to 3.3V, so perhaps there has been an undocumented update to the hardware to match the more common 3.3V levels. Our board is marked version 1.41. One GPIO feature of the ROCK 4C+ that the Pi 4B lacks is an ADC (analog-­ to-digital converter); we can’t recall any other single-board computers that have an integrated ADC. This pin appears to be only connected to the ADC, so it cannot be used as a digital input or output. The ROCK 4C+ also supports an optional eMMC module (and Radxa offers such modules and adaptors for working with them), which it can also boot from. eMMC stands for embedded multimedia card and usually provides better performance and endurance than a microSD card. eMMC is an often-requested feature for the Raspberry Pi range, so clearly, Radxa is listening to its potential customers. The ROCK 4C+ can also boot from SPI flash, and the pins to do this siliconchip.com.au Photo 2: there are few surprises on the back of the ROCK Pi 4C+ except the optional eMMC module socket. Radxa sells eMMC modules and adaptors for those wanting storage beyond the standard microSD card. Photo 3: the main connectors of the ROCK Pi 4C+ are in much the same locations as those on the Pi 4B. The provision of a footprint for an (optional) SPI flash memory chip is sure to be handy for certain users. Table 1 – comparison between the ROCK 4C+ and Raspberry Pi 4B ROCK 4C Plus Raspberry Pi 4B RockChip RK3399T (6 cores) Dual 1.5GHz ARM-Cortex A72 + Quad 1.0GHz ARMCortex A53 1MB + 512KB L2 caches BCM2711 (4 cores) Quad 1.8GHz ARM-Cortex A72 1MB L2 cache Processor (CPU) 600MHz Mali T860MP4, four shaders, 256KB L2 cache 500MHz VideoCore 6, 1MB L2 cache shared with CPU cores GPU two micro-HDMI, up to 4K + 2K (60Hz with one or both) two micro-HDMI, up to 4K + 4K (60Hz with one or 30Hz for both) Display output HD stereo, up to 24bit/96kHz Stereo, PWM-based Audio output 4GB 1GB, 2GB, 4GB or 8GB RAM 5V/3A, USB-C or pin header 5V/3A, USB-C or pin header Power requirements 2× USB2, 2× USB3 2× USB2, 2× USB3 USB 1× Gigabit 1× Gigabit Ethernet 802.11 b/g/n/ac (WiFi 5) Bluetooth 5.0 u.FL antenna 802.11 b/g/n/ac (WiFi 5) Bluetooth 5.0 PCB antenna Wireless 40-pin header: 1× PWM 2× SPI channels 2× I2C channels 1× ADC (analog) channel 40-pin header: 4× PWM 2× SPI channels 2× I2C channels I/O Australia's electronics magazine April 2024  59 Screen 1: the Debian 11 image is the only official image with a usable graphical desktop environment. The desktop is quite familiar, even to those who may not have used Linux before. are available on the GPIO header or as an unpopulated footprint on the PCB. The ROCK 4C+ includes an RTC (real-time clock) chip; its function is part of the PMIC (power management IC), although it does require an external battery to provide backup power. The presence of an RTC is helpful, although marginally so, as NTP (network time protocol) is readily available through the internet. The MIPI (mobile industry processor interface) camera and display connectors are different from those on the Raspberry Pi boards, so we couldn’t try them out using the official Raspberry Pi displays and cameras. Adaptor cables exist that should allow the official Raspberry Pi devices to be used with the ROCK 4C+. Hands-on testing Screen 2: the Discover app allows other apps to be installed. We installed the LibreOffice Writer word processor and the Arduino IDE with ease. We even wrote part of this article on the ROCK. With the ROCK 4C+ being very similar, feature-wise and in general size and layout, to the Pi 4B, we need to look at software and support to see the differences. Like the Raspberry Pi computers, various Linux operating system (OS) images based on Debian and Ubuntu are available for installation, as well as an Android image. We started with the Debian distribution as this would theoretically be the most similar to the Raspberry Pi OS (formerly ‘Raspbian’). Installing the OS is much the same as for other single-board computers and requires a disk image file to be written to a microSD card. The zipped files for the ROCK 4C+ can be downloaded from https://wiki.radxa.com/ Rockpi4/downloads That page also has files for other ROCK boards, so be sure to choose the correct tab before downloading! We used a 3A USB Type-C mains power supply designed for use with a Raspberry Pi 4B, and it worked fine. You will also need one or two micro-HDMI to full-size HDMI adaptors (type-D male to type-A female) or cables, plus a USB keyboard and mouse. Debian Screen 3: the Ubuntu distribution only offers a command line interface (CLI) on the ROCK 4C Plus. Still, it was pretty easy to connect to a WiFi network and update the operating system. 60 Silicon Chip Australia's electronics magazine Screen 1 shows the Debian desktop after booting up, installing updates and basic configuration, such as connecting to WiFi. The Firefox web browser is pre-installed and shows the Radxa ROCK 4 operating system downloads page. siliconchip.com.au We were also able to install the free LibreOffice Writer word processor and actually wrote some of this article on the ROCK 4C+ using this software. Apps are easily installed through the Discover app, as shown in Screen 2. We found the Writer word processor app was quite functional, but the ROCK 4C+ struggled if a few web browser windows were open at the same time. All the included software was functional and intuitive enough to find, install, and use, but it tended to be a bit sluggish. We had no trouble using Bluetooth to send files to another computer. Those with meagre requirements might find the ROCK 4C+ a useful substitute for their Windows PC or as a second machine. The range of included and available software is quite good, but the processor is not fast by modern PC standards. We found many familiar programs ready to install, including the Arduino IDE. For all the time we were running Debian, the main processor chip was quite hot to the touch; it is clearly being worked very hard. We didn’t try any heatsink or fan options, but they may be worth considering for prolonged use in this role. Ubuntu The Ubuntu distribution available for download is actually a commandline-only server edition; its boot screen is shown in Screen 3. It is intended for users who prefer a command line interface, although there is a good introductory guide at https://wiki.radxa.com/ Rockpi4/Ubuntu The distribution is set up for headless operation (without a keyboard or display) and has an SSH server enabled by default. This could be a good way to get started with command line Linux, as the guide has information about using Bluetooth, WiFi and the GPIO header from the command line. It would be suitable for use as a web server, file server or similar roles. If you manage to corrupt the installation, it is easy enough to reflash the operating system image to the microSD card to recover it. Android We tried the Android 11 image available on the downloads page. It is currently the oldest supported version of Android, with version 14 being current. The Android system was siliconchip.com.au Screen 4: the Android operating system image had a few glitches that we could not easily resolve. As a result, we could not thoroughly test it, but most of the things that we tried worked as expected. functional (with a mouse instead of a touch screen), although it is apparent that the diminishing support affects usability. Screen 4 shows the home screen; the white banner at the top could not be dismissed and continued to sound an alert. That could only be muted by turning down the notification volume. Some of the installed apps needed to be updated to work, but we couldn’t do so due to the Google Play Protect error. So, the Android image will mainly be useful if you have a specific app you wish to run and can install without using the Play Store, for example, by side-loading the APK. After testing this, we came across a forum post explaining a multi-step process that can get rid of this error message and allow Google Play Services to run on the ROCK 4C+ but we have not tried it. You can find the instructions at siliconchip.au/link/absj Other options The downloads page lists around ten other third-party operating system distributions, including options for media centre use and game emulation. So it appears the ROCK 4C+ has broad community support for many operating systems. Forum The communities that have developed around ecosystems like the Raspberry Pi computers and the Arduino IDE have been instrumental in their usability and thus broad acceptance. The Radxa forum (https://forum. radxa.com/) is handy for engaging Australia's electronics magazine with other ROCK board users and finding answers to common problems. While trying out the ROCK 4C+, if we could not find where to change a particular setting, an internet search usually led us back to the forum and the answer to our question. Summary The ROCK 4C+ is an interesting alternative to the Raspberry Pi Model 4B. It has certain features, such as the optional eMMC module, that could give the edge to users with specific use cases. The analog (ADC) input on the GPIO header is another feature that could be very handy under some circumstances. The Debian distribution offers a decent desktop computer experience, even for those who have not tried Linux before. It will undoubtedly be familiar to anyone who has worked with Raspbian or Raspberry Pi OS. We don’t think it’s ready to replace a desktop computer completely, but it could be handy for light duties or as a second machine. Other distributions could turn the ROCK 4C+ into a games machine or media centre. At the time of writing, the ROCK 4C+ retails for about the same as a Raspberry Pi Model 4B. Altronics is selling the ROCK 4C+ (Cat ZR6302G) for $133. Order one before the end of April and get a free USB QC3.0/PD power supply/charger (normally $29.95). Jaycar is also selling the ROCK 4C+ (XC9300) and has a special price for Silicon Chip readers – see the inner front cover advert for details. SC April 2024  61