I wanted to interface an LED circuit with smartphones without microcontrollers. Research showed that IC 34825, a 20-pin IC can be used for the interfacing purpose. Also an evaluation board for the same is available. But I could not find anything 'specific' for any detailed use of the IC with respect to Android. Could anyone point me to some?

Okay, Let's cut the cheese. I'm leaving the specifics. How can I convert a data word written to a USB port of say a smartphone into signals of multiple HIGH-LOW bits without a microcontroller. I mean, Is there an IC?

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    \$\begingroup\$ That chip is for the host side, not the device side. \$\endgroup\$ Oct 21, 2016 at 14:56
  • \$\begingroup\$ Since USB is USB, it should be able to interface a smartphone, right? I just wanted to know, if.. any project is available. I couldn't find any. \$\endgroup\$ Oct 21, 2016 at 14:58
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    \$\begingroup\$ That chip is intended to be part of the smartphone itself. \$\endgroup\$ Oct 21, 2016 at 15:02
  • \$\begingroup\$ What about the Evaluation Board? \$\endgroup\$ Oct 21, 2016 at 15:03
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    \$\begingroup\$ That IC doesn't do any manipulation of the USB data, it's just there to simplify the detection of chargers and OTG devices. I think what you want is something like sparkfun.com/products/13613 or nanorivertech.com/usb-adapters.html ; oh and there is no general way of "writing a data word to a USB port", it has to be some specific kind of USB device. \$\endgroup\$
    – pjc50
    Oct 21, 2016 at 15:40

1 Answer 1


The IC 34825 is an analog multiplexer chip that provides different auxiliary functionalities over a USB connector on some device. Depending on pull information on the ID pin and its value, the USB pins can switch and provide different function, ether as audio signal, or debug functions via UART. This is up to whatever is connected through the cable, and up to the unspecified device to decide if it wants to provide this extra functionality. The IC itself does not provide any USB functionality, it just passes USB through unless instructed otherwise by either the ID pin, or I2C interface.

Regarding the final question, if there is an IC that converts some USB data into flip-flop of few digital bits without MCU, it is difficult. Because "USB is USB", which implies a full UNIVERSAL serial interface mechanism that supports all these USB IN-OUT-ACK-NAK serial tokens, with necessary correct responses to get_descriptor etc.,, identifying itself as a certain class of devices, so the host can load a proper driver. Which again implies that you can't simply "write a dataword" into some "USB port" in your smartphone, but rather you need to send some messages to proper device. Because USB is USB.

The easiest way to accomplish the bit-flipping task is to get a u-controller from, say, Cypress, CY7C63803, and program it properly. Or you can get the entire ready-to-go USB device from WWW.J-WORKS.COM.

Alternatively you can look into FTDI FT240x chip (FIFO), maybe there is some hardware configuration that will allow to use it as a single-word parallel port, but I am not sure if this is possible without some additional handshake logic. If you can find it out, please share your findings.

  • \$\begingroup\$ I think the easiest way to interface something with a random smartphone is through Wifi or Bluetooth. There are Bluetooth I/O modules out there, like this one: numato.com/8-channel-bluetooth-gpio-module \$\endgroup\$
    – Janka
    Oct 21, 2016 at 22:55
  • \$\begingroup\$ There is a less expensive (and likely more reliable) GPIO module, numato.com/8-channel-usb-gpio-module-with-analog-inputs using PIC microcontroller \$\endgroup\$ Oct 22, 2016 at 0:22
  • \$\begingroup\$ Slightly disagree because I had so much bad USB hardware (devices, PC hosts and phones – bad in two ways) in the last years. USB is pretty unreliable as soon you want to use it 24/7. Most prominent failure was power management. \$\endgroup\$
    – Janka
    Oct 22, 2016 at 8:24
  • \$\begingroup\$ No, no, I didn't mean to say that USB is reliable. I just feel that fluctuating wireless is worse that a wire. The common USB relies on continuous traversing of main user memory, which has no error correction, and nearly unrestricted access from any junky application, so the USB should not work at all, and if it works, it is a sheer luck.:-) \$\endgroup\$ Oct 22, 2016 at 15:45

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