An interesting, but perplexing expansion board for the Raspberry Pi

Expansion board for Raspberry Pi
This afternoon our Twitter stream informed us of the existence of this thing: An Expansion Board Made for Raspberry Pi made by a company called SupTronics, which appears to be headquartered in Shenzhen, China. It can be purchased from this site, and the specifications can be found here. Quoting from that page:


The X100 expansion board designed for use on the Raspberry Pi (RPi) computer platform. The board supplies RPi with a regulated +5V from a wide-range voltage source and also contains a real-time clock, a RS232 master port, a HDMI to VGA converter, 3-port USB hub, memory card reader, and 8-channel darlington Driver.  
Main Features
  • Exactly same size as Raspberry Pi (85 x 56mm)
  • Directly installed into the GPIO header pins with no wiring or soldering
  • 6-23V input to 5V, 3A high-efficiency step-down DC/DC converter to supply your RPI
  • Supports HDMI to VGA (NOT powered by the RPI’s HDMI port)
  • Supports self-powered USB hub (Total 4 ports available)
  • Supports self-powered SD and Micro-SD card reader
  • RTC based on NXP PCF2127AT / PCF2129AT with CR2032 backup battery
  • RS232 Serial Port
  • Having the reset switch convenient to enable RPi reset facility
  • Having two slots to make use of RPi’s FPC connector (S1 & S5)
  • Allowing to stack along with other expansion boards.
  • 8-channel darlington Driver chip allowing to control electronic circuits which require more current to drive them
  • Have DIP switch to remove connection from RPi’s pin header so as to keep using other expansion board with no effect.
 * This expanson board is suitable for Raspberry Pi Rev 2 Model B.

We haven’t actually had our hands on the device, but our initial impression is that it adds a bunch of things that might each be individually interesting to a certain subset of Raspberry Pi owners, but in most cases it will be priced too high to get that one feature you really need, and if you only need one of those features you can probably build it yourself or find a cheaper way to add it. Let’s take each actual feature in turn:

6-23V input to 5V, 3A high-efficiency step-down DC/DC converter to supply your RPI

This in and of itself is great if it works, since the Raspberry Pi is notoriously finicky about power supplies (use one that’s not quite stable enough and you’re likely to have occasional SD card corruption). But a good power supply wouldn’t cost nearly this much. However, if you want to install a Raspberry Pi in a vehicle that only has a 12 volt supply available, or some other situation where the available power is unstable, then this become a more desirable feature.

Supports HDMI to VGA

WHY? Who uses VGA anymore? Oh, right, this came out of China, where the first world dumps all its CRT monitors that nobody wants anymore. We’d have much rather seen this relatively ginormous space used to provide improved audio capability; perhaps a S/PDIF connector supporting full 5.1 or even 7.1 audio. That would have been something we could actually make use of.  And why do they use the word “Supports” to mean “This is included on the board”?

Supports self-powered USB hub (Total 4 ports available)

It appears this means that it includes 4 USB ports. Which is great if you need them, but you can buy powered USB hubs for less than what this costs.

Supports self-powered SD and Micro-SD card reader

Again this is a rather strange way to word this, because the card reader is on the board. Since the Raspberry Pi already has a SD card slot, what’s the advantage of having one on this board? For many users there will be none.

RTC based on NXP PCF2127AT / PCF2129AT with CR2032 backup battery

This is really only useful if you are using your Raspberry Pi in a situation where you can’t update the time from an Internet-based timeserver. And even then, it only matters if keeping something close to the exact time is important to your application. Again, we could see this being most useful in a vehicle-based application.

RS232 Serial Port

This is so early 2000’s. A rare few people might have a use for this (and for those that do, we suspect that add-on serial port circuits are available for less than this) but for most people this is just a useless port that wastes space that could have been occupied by something useful, like maybe a Wi-Fi or Bluetooth module, or any of a number of things that might actually be useful to people in this decade.

Having the reset switch convenient to enable RPi reset facility

A switch that costs less than a dollar to add is hardly a reason to buy this board, but at least it’s more useful than some of the other things they put on here. But, why not a true power switch, that (when used with some software) would do a proper shutdown on the Raspberry Pi? That would have been far more useful. And, viewed one way, giving people easier access to a cold reset is not such a great idea, since every time you use it you risk corrupting your SD card. Yet we understand that it can be a convenient feature if the Raspberry Pi is prone to freezing up occasionally.

8-channel darlington Driver chip allowing to control electronic circuits which require more current to drive them

This appears to be basically a ULN2803A integrated circuit with the outputs brought out to some inconvenient connectors. It’s described this way:

ULN2803 8-channel RC servo port
Bring in some muscle to your output pins with 8 mighty Darlingtons! This driver chip contains 8 drivers that can sink 500mA from a selecable 5V or input voltage supply and has kickback diodes included inside for driving coils. This will let your little microcontroller or microcomputer power solenoids, DC motors (in one direction) and unipolar stepper motors. The GPIO Pins are connected to ULN2803 inputs through a DIP switch, with the its outputs going to two array of Wire-to-Board header. Alternatively, these ports can be used to supply +5V or input voltage to other external circuitry, or embedded devices.Please note that this is an ‘open collector’ driver – it can only be used to connect the load to ground and there will be a 1 Volt (or more) ‘drop’ across the internal transistors.

For some people this might be the most useful thing on this board, although it would be nice if there were better documentation on how it’s used. It appears that this converts the Raspberry Pi GPIO ports to make them behave more like those on an Arduino, though we can’t be entirely sure. But you can do the pretty much the same thing same thing with a cheap breadboard, a ULN2803A (get the kind with long pins, not the surface mount type), some connector wires, and an external power supply. Here you get all that in one package (except you will still need the external power supply), but why on earth did they add those funky little white GPIO connectors on the board? We realize those appear to be similar to the type used to bring power to certain devices (such as some internal drives) but still, the plugs that fit those connectors are not something that the average person is likely to have lying around.

Basically, it’s our opinion, again based solely on the information we can find online, that this will only be a good fit for people that happen to need several of these features, or that simply have money to burn and no inclination to look for other ways to achieve the same results. And (at least in the first world) relatively few people will have use for a VGA port, and probably even fewer for a serial port. We can see some of the other features being a bit more useful, particularly in vehicle based and remote sensing applications, or cases where you plan to power this off a solar or wind-powered source of electricity.

If there is ever a second revision on this board, we would recommend the following:

– Ditch the VGA port and replace it with a S/PDIF audio output.
– Ditch the serial port and consider replacing it with a wi-fi and/or bluetooth connection
– Change the reset button so that it becomes a true power on/off button, so that when the power is turned off it signals the Raspberry Pi to do a graceful shutdown (the equivalent of typing sudo poweroff at the command prompt) and then waits for that shutdown to complete before removing the power. We would expect that you’d need to run a background task to catch the shutdown signal and run the shutdown sequence, but you have to install additional software to make the RTC work, so this would simply be similar to that procedure. And several people have built standalone devices that do this, so it’s definitely possible, and this would be far better than giving a typical user an easy way to do a “cold” reset that might bork their system.
– Add a receiver for an infrared remote (suggested by Jeff Darlington in the comments section)

We neither recommend this board nor advise against it, we’re just saying that depending on the reasons you’d want to use it, there might be better or less expensive options. But if you can utilize several of the functions on this board, then it might be a good value for you, assuming that it works as advertised and that if you plan to use the GPIO connections, you can actually figure out how you’re supposed to connect to them.

2 thoughts on “An interesting, but perplexing expansion board for the Raspberry Pi

  1. For me the VGA port is significant, I want to use it for a low power device to feed and decode video to my JVC projector, which being archaic ie circa 2001, only supports vga or rgb inputs. I currently use a computer with a 400 watt power supply to feed the image to the projector. It would be great to use my Raspberry PI, strapped to the back of a vga lcd monitor.

    Its a great way to recycle an old monitor and lower the heat in summertime, since the 400 watt lamp on the projector is toasty enough.
    I’m waiting for my X100 expansion board to arrive and we’ll see if its up to the task.

    here’s the mfg’s page with info on how to implement some of the ports etc.

    btw you can get s/pdif with a usb sound card and it allows for a little more flexible placement of the cabling.

    It is truly a swiss army knife of expansion boards, I was surprised they didn’t add an IR port and a remote control, which for my taste would
    be very useful. Lots of things on this little board, I guess everybody wants something different.

  2. Unfortunately Raspberry came with no standard devices….
    Usb should support until 500mA…I cant ‘connect an extenrnal HDD wihtout an HUB usb and price for a powered hub is about 15€….i wanna connect my rapsberry to a VGA monitor, I bought a converter cable on ebay (9eur) but with same problem: if it s not powered it could not working or working until diode will burn… my case the cable doesnt work with rasberry….
    so right now i ve spent 24€ (unusefully in case of hdmi converter) and I need more spoces for 2 more devices….
    To have my vga converter working I need to buy a powered converter….The cheaper I found is 20eur….
    I’m thinkning to buy this expansion board.
    It could be good if it had a buzzer and an IR receiver….anyway for 27 eur it s good.

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