I have an Apple //e, and I quite enjoy using it as a dumb terminal to my Raspberry Pi from time to time. Recently, I came across a few cords that could connect my Android phone (a Pixel) to the DB25 port on the back of the //e's Super Serial Card.

Is there any software I could use to get my Android phone to interact with the Apple? I am using MODEM.MGR currently whenever I connect it to my Raspberry Pi. Is there an app for Android that anybody can verify works with an Apple II Super Serial Card's DB25 port?

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    – wizzwizz4
    Commented Jan 9, 2017 at 21:06
  • Where is this DB25 port? Is it a serial port on a Super Serial Card? Commented Jan 10, 2017 at 1:31
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    Yes, I forgot to mention that I am using the Super Serial Card. Commented Jan 10, 2017 at 3:43
  • I assume the "cable" is a serial USB device and not just a "cable", or of course it won't work. Those devices typically have a DB9 connector, so a DB9-to-DB25 converter for serial ports will probably also be part of the "cable".
    – dirkt
    Commented Jan 10, 2017 at 14:35
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    Did you test the "cable" by using it to connect the Apple and the RaspPi? Does it work? Possible gotcha with "cables" (USB serial ports): Some use +5V instead of RS232 voltages, and this can cause trouble with old serial ports like in the Super Serial Card. In doubt, measure.
    – dirkt
    Commented Jan 11, 2017 at 11:39

2 Answers 2


Most (though not quite all) Android devices support operating the USB port as a USB host, either triggered by the usual OTG role pin on an adapter cable or by vendor-unique software setting. There can be various complex interactions with charging and ability to supply power to a peripheral, but for a low consumption device like a USB serial converter it will in most cases work, though obviously consuming power from the phone battery.

On the software side, Android allows Apps to interact with the USB host mode through a fairly low-level API, so in effect Apps have to bring their own user-mode USB driver implementation built with detailed understanding of how to talk to a particular peripheral. USB serial converter chips tend to be well and widely understood in the technical community, so for the major varieties you should be able to find a pre-made app or perhaps an open source codebase to leverage - but you will need one compatible with your particular converter. If you run into difficulty it may be easiest to try another - don't rule out 9-pin devices with a 9-to-25 pin adapter.

The last level would be having serial line settings and data interpretation compatible with the //e and whatever you are trying to do with it. This is where starting with an open source Android App could be beneficial as you could then customize it to best support what you are doing with the Apple.

As an alternative to USB, you could also look into using a bluetooth to serial module (on Android, classic BT would work better for this than BTLE), or perhaps making a serial-to-wifi bridge out of a small router or something like an ESP8266.


I do not expect it is practical. The reason you can connect the Apple to RPi is that the USB port on the RPi is designed to be a host to USB slave devices - for this case, it is hosting a USB slave that does RS-232. And, perhaps more importantly, the RPi has drivers installed that can recognize RS-232 capable hardware and use it as a terminal connection. So the RPi controls the RS-232 slave, and the slave and Apple computer exchange data with one another over RS-232. The Android phone also has a USB port, but it is commonly only used for charging and for connecting to a host (like the RPi). The Android hardware, or the available drivers, does not support slave devices like the USB-to-RS-232 device, nominally.

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    Most Android phones have a USB OTG port, which can switch between the "host" and "device" roles.
    – Mark
    Commented Jan 25, 2017 at 5:56
  • Thanks. I amended the answer to point more toward the necessity for both hardware and driver support on the Android device which can be taken for granted on the RPi.
    – Brian H
    Commented Jan 31, 2017 at 3:07
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    Well, I can view some information in the DroidTerm app. It says: "Usb Device not supported: MCS7820/MCS7840 2/4 port serial adapter Vendor: MosChip Semiconductor". Since it recognizes the device, I assume it is possible to write to it. However, I would likely have to write that myself, and I don't know where to get started. Commented Feb 19, 2017 at 21:50
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    @ZacharySwanson, you might try different cables. One of them is sure to use the ubiquitous PL2303 USB-to-serial adapter, which Android is quite likely to have a driver for.
    – Mark
    Commented Mar 2, 2017 at 6:48
  • @BrianH this continues to be an effectively incorrect answer. Android has for many years now allowed what are effectively user-mode USB device drivers to be included in Apps. Commented Mar 2, 2017 at 16:47

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