reTerminal is missing something important

There comes a time in the maker’s life when they need something fancy, cool and Raspberry Pi based. While joyous products like CrowPi2 and RaspPad3 bring interesting and unique takes on your favourite SBC, SeeedStudio takes it a step further. By removing the bulky form factor of the regular RasberryPi 4 and utilising RaspberryPi Compute Module 4 instead. reTerminal brings a new exciting touchscreen interface inside a rugged, industrial case. Is it enough to catch your attention? It got mine!

A terminal with an industrial side

I had an eye on reTerminal for some time. Despite being familiar with the device’s product page I completely misjudged the size of the device. Product pictures included on Seeed’s website don’t portray how portable reTerminal is. I imagined something chunkier and bigger in size, while in reality reTerminal fits nicely in one hand and impresses me with the industry-grade build quality of the gadget.

Don’t dismiss the plastic enclosure. It feels great in my hand while the massive aluminium heatsink at the back adds to the heft of the panel. Buttons feel clicky and satisfying while 11 brass screw inserts (10 x M4, 1 x 1/4″) offer a virtually infinite way of mounting reTerminal. 4 programmable LED status lights come in handy to quickly display the operational status of the module, while 5″ ISP panel 1280 x 720 and 293 PPI density – crowns the panel with a practical capacitive touch interface.

I/O

Compute Modules aren’t famous for their I/O, and Seeed Studio took an interesting turn in breaking the most popular I/O in reTerminal. The device comes with:

• USB-C (power)
• 2 x USB 2.0
• mini HDMI
• RJ45 Ethernet (1Gbit)
• 40 pin GPIO header
• HSI connector
• 5 buttons

The module inside is a 4GB RAM version of the Raspberry Pi Computer Module 4 with the integrated 32GB eMMC storage. It comes with all the bells and whistles of the Raspberry Pi 4 like dual-band 2.4GHz/5GHz Wi-Fi and Bluetooth 5.0 BLE.

High-Speed Interface

Instead of breaking out the PCIe lane as USB 3.0 ports like it’s done on Raspberry Pi 4 boards, reTerminal uses the PCIe single lane host (5Gbps) to enable the HSI connector hidden under the rubber cover at the back. This connector may not appeal to a typical maker, but access to a high-speed interface like this will be advantageous to anyone willing to develop add-ons and modules compatible with reTerminal. The first expansion is available now and you can read more about reTerminal E10-1 and what this add-on brings to the table.

All this goodness is sprinkled with a touch of extra sensors integrated into reTerminal. You will also get RTC (NPX PCF8563T), accelerometer (STM LIS3DHTR), light sensor (Levelek LTR-303ALS-01)and a buzzer.

Not everything is there

The list looks overwhelming already, but there is one thing that reTerminal is missing, none of the HSI add-ons teased by Seeds Studio is available as of yet. At the time of the writing, there is no dedicated battery pack for this device, even though you can power it up by supplying a 5V/2A through GPIO header. I understand that industrial applications wouldn’t care about the battery, but Seeed Studio is known for providing excellent devices for makers and not having this add-on available simply feels odd.

Buyers should also bear other limitations in mind. reTerminal comes with digital GPIO pins only. Anyone looking to hook up analogue inputs will be disappointed (Compute Module 4 limitation). PWM pins are limited to one.

With enough I2C, UART and SPI interfaces, adding modules that support missing functionalities shouldn’t be a big problem. While Seeed Studio promises to utilise the HSI to add exciting modules, it has been 8 months since the launch and no extra modules are available. I hope to see options soon from promised mic array & speaker, camera, industrial I/O, LoRaWAN, 5G/4G, and PoE.

It’s a shame that until the add-ons happen, the PCIe and USB 3.0 is locked behind the HSI socket. Average maker won’t be able to access that without external modules. I think SeeedStudio has made a big mistake, not releasing it with an HSI extension which would open up some of the interfaces locked behind the proprietary socket. reTerminal is nice, but anyone getting one will feel like they purchased a product with locked away features.

Inside

Despite the solid enclosure (bear in mind, it’s not rated for water and dust protection) it’s easy to peek inside. reTerminal uses a carrier board to provide all the functionality. It’s great news for anyone looking at swapping the module for an 8GB RAM version or just assigning the CM4 for another use case.

Hidden inside lays a microSD card reader should you wish to load another version of RaspbianOS or experiment with Linux distros. Anyone looking for vision-enabled projects will be happy to see CSI connectors (yes, 2 of them (15 pin and 22 pin version) and a dedicated slot at the back of the case to feed the ribbon cable through. If you are keen on trying out the HQ Raspberry Pi camera – reTerminal has got you covered.

If Raspberry Pi Foundation continues with the CM form factor, further upgrades will be also possible.

In use

Tech spec, PCBs and datasheets are all cool, but it means nothing unless reTerminal is fun to use. I plugged it in and tried it for myself to figure out who would benefit most from getting a unit for yourself.

Unlike RasPad 3, reTerminal is ready to go. Once I removed it from the box, added a USB-C 3A power supply I was greeted with a custom installation of Raspbian OS and a demo app on the desktop. It loaded quickly (20 sec boot time) and it feels responsive.

Touch me if you can

The 5″ ISP display (720p) is an actual highlight of the panel. With wide viewing angles, accurate touch representation and 60 FPS it’s perfect for the job at hand. Even if you have to deal with default scaling of the Rasbian OS and onboard – the onscreen keyboard. Even my hardened from assembling industrial robots, fingertips didn’t have issues operating menus. If there is anything I would improve, is the double click speed. The default one is a bit fast for the touchscreen interface.

The shoulder button wakes up the device while the 4 button front panel allows the user to configure it to your liking. By default, the buttons are linked to some random keystrokes. Rebinding or using these as input won’t require rocket science.

Thermals

The inclusion of the massive heatsink promises decent heat dissipation. To put that to the test I run CPU intensive benchmarks. At the ambient of 20℃, the device runs cool at 35℃ thanks to its passive cooler.

Ramp up the efforts with a 45 min stress test and the situation changes. The temperature slowly rises to 55℃ and saturates the heat dissipation rate by the big radiator. The cooling performance is pretty good but there is a catch. It’s cooled passively, it takes forever to emit all that stored heat. It took approximately 40 min to return the CPU temperature to the “pre-test” levels.

I had some time on my hands, and I do these tests often enough that I made an entire interface in NodeRED. Feel free to give it a shot if you think you could benefit from that flow.

WiFi & Ethernet

To verify the network performance I used the iperf3 test to quickly test the speeds over 2.5GHz and 5GHz WiFi and test the good old RJ45 connection.

Interface	Speed (as receiver/sender)
1Gbps Ethernet	926 Mbits/sec | 936 Mbits/sec
2.4GHz in ideal conditions	45.7 Mbits/sec | 45.0 Mbits/sec
5 GHz in ideal conditions	93.0 Mbits/sec | 90.4 Mbits/sec

The 2.4GHz bandwidth struggled a little bit, but if I factor in my ZigBee network cross-talk, it won’t be far off to what’s expected from Raspberry Pi 4.

Storage

If included 32GB of eMMC storage isn’t enough, storage can be expanded by microSD card (slot inside) or via USB. Baked into the PCB storage is respectable too. Quick read/write tests bring the following results:

dd if=test of=/dev/null bs=1048576
209715200 bytes (210 MB, 200 MiB) copied, 0.395081 s, 531 MB/s   #READ
dd if=/dev/zero of=test bs=1048576 count=200
209715200 bytes (210 MB, 200 MiB) copied, 1.72545 s, 122 MB/s   #WRITE

Final Thoughts

Thanks to multiple attachment points, reTerminal cab be mounted on virtually anything. It’s a solid device with a great IPS panel and touchscreen. I will spend some time using it to visualise the data from my automation as the included demo program gave me some ideas. If you are looking for a handy terminal panel with a RaspberryPi 4 inside – reTerminal is definitely an interesting choice as long as you are happy with the limitations listed in this article. Seeed Studio made it available for $195 (with CM4 included). I for one, can’t wait to see what HSI add-ons will become available in the future. Let me know what do you think about it and how would you use it in this Reddit thread.

🆓📈 – See the transparency note for details.