Project image
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$805
pledged of $1,500pledged of $1,500 goal
23
backers
Funding Unsuccessful
The project's funding goal was not reached on Mon, September 8 2014 11:52 PM UTC +00:00
$805
pledged of $1,500pledged of $1,500 goal
23
backers
Funding Unsuccessful
The project's funding goal was not reached on Mon, September 8 2014 11:52 PM UTC +00:00

About

Link to Tindie Store

Like a lot of folks we got excited when the Raspberry Pi was first announced. We couldn't wait to get our hands on our first board. When our chance came to get a Pi we also bought a prototyping board so we could connect up our own devices to the Pi. We anxiously awaited the arrival of our card. It felt like our card would never arrive.

While we were waiting, we dug deeper and found out that the Raspberry is limited to 3.3V I/O and we realized that the GVS devices we already have  for our Arduinos are 5V parts that would not work with our Raspberry Pi. Sure we could adapt one of the 3.3V to 5V converters out there but that sounded like a lot of work. What we really wanted was a way to allow our 5V GVS parts to connect to the Raspberry Pi without a lot of hand wiring but we couldn't find a card out there that does the 3.3V to 5V voltage conversion that our 5V parts need.

Add to that the recent announcement of the new Raspberry Pi Model B Plus which has additional GPIO pins. The new board increases the USB port count from 2 to 4 which makes perfect sense to us since we like to connect a keyboard, mouse and wireless adapter to our Raspberry Pi.

There were no cards out there so we designed a card to meet our needs, the Raspberry Pi-Plus-GVS

GVS Board for the Raspberry Pi Model B+
GVS Board for the Raspberry Pi Model B+

If you have one of the older Raspberry Pi Model B cards we also have a GVS cape for the Raspberry Pi Model B on kickstarter. If you have a Beaglebone Black we also have a GVS card for the BBB.

The RasPi-Plus-GVS card allows your Raspberry Pi Model B Plus to communicate with 5V devices by performing voltage translation from the 3.3V of the Raspberry Pi B plus to the 5V of most GVS parts.

The RasPi-GVS card provides Ground, Voltage and Signal (GVS) connections to all of your 5V devices so you don't have to worry about power and ground routing from the Raspberry Pi 5V power signals.

This board is modeled on the Arduino Sensor Shields, also known as GVS shields. Arduino Sensor Shields bring out the pins of the Arduino to GVS (set of Ground, Voltage and Signal) pins.

Note: This card only works with the latest Raspberry Pi B Plus card. This is the card with four USB connectors and the Micro SD card.

Features

  • Daughtercard to the Raspberry Pi Model B Plus (you supply the Pi) 
  • (2) 8-bit, 3.3V to 5V bidirectional voltage translators on 16 Raspberry Pi GPIO lines
  • (7) 5V GPIO lines on GVS connectors
  • (2) 5V SPI interfaces (can be used as 5 GPIO lines)
  • (1) 5V UART interface
  • (1) 5V I2C interface (can be used as 5 GPIO lines)
  • GPIO_4 enables/disables the 5V voltage translators
  • (9) 3.3V GPIO interfaces 
  • Resettable Fuse protection on the 5V power lines
  • Power Supply which can power the GVS connectors (within limits)
  • Raspberry Pi B+ card connector
  • Jumper to select power for GVS (allows the GVS connectors to be powered from either the on-board regulator or powered from the Raspberry Pi)
  • Form factor matches the Raspberry Pi B Plus board including the four 2.5mm mounting holes

Voltage Translators

The Raspi-GVS board uses Texas Instrument TXS0108 voltage translators.

Voltage Translators Features

  • No Direction-Control Signal Needed
  • Max Data Rates 60 Mbps (Push Pull) 2 Mbps (Open Drain)
  • 1.2 V to 3.6 V on A Port and 1.65 V to 5.5 V on B Port (VCCA ≤ VCCB)
  • No Power-Supply Sequencing Required – Either VCCA or VCCB Can Be Ramped First
  • Latch-Up Performance Exceeds 100 mA Per JESD 78,
  • Class II ESD Protection Exceeds JESD 22 (A Port)
  • 2000-V Human-Body Model (A114-B)
  • 150-V Machine Model (A115-A)
  • 1000-V Charged-Device Model (C101)
  • IEC 61000-4-2 ESD (B Port) ±6-kV Air-Gap Discharge

What is GVS?

GVS is great for prototyping or deploy-able products. The beauty of the GVS connection is that power and ground are provided with each I/O signal. That provides the power needed to power external sensors and output devices. Otherwise splitting the one or two power pins into separate cables ends up being a real mess.

GVS stands for Ground, Voltage and Signal. It's a 3-pin unofficial standard. It uses 0.1" pitch pins. There are a large number of GVS sensors (inputs) and devices (output) parts on ebay although they are not called GVS sensors typically. They are identifiable by the three pins and the silkscreen near the pins as GVS sensors. Even sensors which don't have the GVS pin ordering can still be used they just require a cable with wiring other than 1:1.

Testing

Our video above shows that we were able to set all (14) 5V and (9) 3.3V GPIO channels to outputs and set one of the GPIO lines high at a time. This demonstrates the connection is made from the 3.3V side to the 5V side. We also tested with GVS input devices and they worked great as well.

The only thing remaining was testing the UART lines. We found this page and when we tried it the UART worked as well.

All in all, we are confident that this is a fine card.

Risks and challenges

We built a prototype card and it works great. We have local talented assemblers and feel comfortable that we can scale production if this project is funded. We believe that others will see the value of this card.

One of the biggest challenges we anticipate for this board is timing. Are we just too early since the card just came out? We spent our summer vacation working on this card and think others might be as excited as we are about the possibilities for the new Raspberry Pi Model B+. That's what we are betting on.

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Funding period

- (32 days)