Secure Mobile Payment Device with Capacitive Touch Pin Pad Interface



Project Description

This project is a great example of the product design capabilities of Blue Sparq, Inc. Zoop actually called us looking for a capacitive touch pin pad for their secure payment device. During their conversation, they got an idea of our product design capabilities and tasked us with creating their first looks like feels like prototype for a trade show that would contain a MagStripe reader, LCD display, PMIC and a capacitive touch keypad.

Blue Sparq, Inc. incorporated its high speed rapid prototyping capability with its Rapid Keypads - Capacitive Touch Keypad Technology to produce this stunning prototype in just a couple of weeks! The mechanical parts were first made using the Blue Sparq FDM machine and then the final parts were produced by a high precision SLA machine. Finally, the parts were given a gorgeous high end paint job!

This project went a long way for Zoop. They presented their ideas to Qualcomm ventures, the investing arm of Qualcomm and won the QPRIZE for the year 2012. They decided to go with us to develop a more complete MPOS solution which was future proof and low cost. The new prototype MPOS will have the following in addition to all the features of the looks like feels like prototype:

  • EMV Chip and Pin card reader
  • NFC/Contactless card reader
  • Bluetooth for communication to iOS and android devices
  • Full Speed USB Interface for firmware updates.

Designing a MPOS involves making a lot of tricky hardware choices. For instance, consider the power supply aspect of this design. Like all modern handheld units, it was required that this device will have a lithium ion battery. This meant the power management solution for the system should

  • Accept external power to charge the Li-ion battery through WALLFB or USB port
  • Seamless transition between input power sources
  • Have atleast 2 high efficiency DC-DC converters
  • Ability to discharge all outputs to ground during shut-down
  • Monitor temperature and stop charging if temperature exceeds Li-ion battery specifications
  • Use a booster if more than 3V is required by any of the other components
  • Will also have a push button similar to modern day cell phones

We used our electrical engineering knowledge and product design experience to choose the right components for this design. A similar exercise was carried out with all other aspects of the design to develop the hardware for the MPOS.

The firmware development involved writing software for the main processor to interact with the various components such as MagStripe reader, Smart Card Reader IC, NFC IC, LCD display, PMIC and a capacitive touch keypad.

To avoid Zoop paying royalties to third parties, the EMV L1 and L2 stack for the Contact Smart Cards and the EMV L1 stack for the Contactless Cards was developed in house by us. The operation of different sections of this stack was tested using the Acquirer device validation tool kit purchased from VISA.

All this work resulted in a Zoop prototype device with the following specifications:

  • Processor: 512KB protected flash and 128KB RAM. 64KB EEPROM
  • Power supply: USB or wall adapter
  • Battery: 3.7V Lithium ion 1590mAh battery
  • Communications: USB CDC device capable of OTG, Bluetooth SPP profile, Apple authentication protocol
  • Display: Chip on glass liquid crystal display module; 2 lines by 16 characters
  • Buttons: 10 numeric, 4 special button and one on/off button
  • LED Indication: 4 LEDs for status indication
  • Magnetic Stripe reader: 3 track bidirectional Magstripe head
  • Smart Card Reader: ISO 7816-3,EMV, GIE-CB standards compatible smart card reader IC
  • Piezo Buzzer
  • NFC Radio

Pictures and videos of this device in action are shown on this page.


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