RPP-UIO-16

Universal I/O Hat for the Raspberry Pi

Board Design

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. Unfortunately, the Raspberry Pi can't work with the same 5V GVS sensors and devices as the Arduino since the Raspberry Pi has 3.3V I/O.

The RasPi-Plus-GVS-Cfg card allows the Raspberry Pi Model B+ to communicate with the same 5V sensors by performing voltage translation from the 3.3V of the Raspberry Pi to 5V.

Features

• All Raspberry Pi I/O lines
• 16-bit bidirectional 3.3V to 5V level translator
• Configuration EEPROM
• Fuses on power
• External 5V Terminal Block
• Raspberry Pi I/O lines

All of the Raspberry Pi Model B+ I/O connections are brought to GVS connectors. This is:

• (17) GPIO lines on GVS connectors
• (2) SPI interfaces (can be used as 5 GPIO lines)
• (1) UART interface (can be used as 2 GPIO lines)
• (1) I2C interface (can be used as 2 GPIO lines)

Example Code/Drivers

• GitHub Repo

Schematic

• RPP-UIO-16 Schematic

Level translators

The RPP-UIO-16 board uses two of 8-bit wide Texas Instrument TXS0108 voltage translator to convert up to 16 of the 3.3V I/O lines to 5V I/O levels.

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 ±8-kV Contact Discharge Voltage Translators Architecture Datasheet

The TXS0108E can be used in level-translation applications for interfacing devices or systems operating at different interface voltages with one another. The TXS0108E is ideal for use in applications where an open-drain driver is connected to the data I/Os. The TXS0108E can also be used in applications where a push-pull driver is connected to the data I/Os, but the TXB0104 might be a better option for such push-pull applications. The TXS0108E device is a semi-buffered auto-direction-sensing voltage translator design is optimized for translation applications (e.g. MMC Card Interfaces) that require the system to start out in a low-speed open-drain mode and then switch to a higher speed push-pull mode.

To address these application requirements, a semi-buffered architecture design is used and is illustrated above (see Figure 1). Edge-rate accelerator circuitry (for both the high-to-low and low-to-high edges), a High-Ron n-channel pass-gate transistor (on the order of 300 Ω to 500 Ω) and pull-up resistors (to provide DC-bias and drive capabilities) are included to realize this solution. A direction-control signal (to control the direction of data flow from A to B or from B to A) is not needed. The resulting implementation supports both low-speed open-drain operation as well as high-speed push-pull operation.

When transmitting data from A to B ports, during a rising edge the One-Shot (OS3) turns on the PMOS transistor (P2) for a short-duration and this speeds up the low-to-high transition. Similarly, during a falling edge, when transmitting data from A to B, the One-Shot (OS4) turns on NMOS transistor (N2) for a short-duration and this speeds up the high-to-low transition. The B-port edge-rate accelerator consists of one-shots OS3 and OS4, Transistors P2 and N2 and serves to rapidly force the B port high or low when a corresponding transition is detected on the A port.

When transmitting data from B to A ports, during a rising edge the One-Shot (OS1) turns on the PMOS transistor (P1) for a short-duration and this speeds up the low-to-high transition. Similarly, during a falling edge, when transmitting data from B to A, the One-Shot (OS2) turns on NMOS transistor (N1) for a short-duration and this speeds up the high-to-low transition. The A-port edge-rate accelerator consists of one-shots OS1 and OS2, Transistors P1 and N1 components and form the edge-rate accelerator and serves to rapidly force the A port high or low when a corresponding transition is detected on the B port.

Fuses

The board has Resettable fuses on the 3.3V and 5V from the Raspberry Pi. These fuses protect your Raspberry Pi from overloads. These fuses are 1 Amp PTC fuses - PTS12066V100 PTC fuses have certain advantages (they are self healing) and disadvantages (they are not like a wire fuse which acts like a switch). If you trust your wiring you may choose to solder a wire over the fuse. Care should be taken when doing so.

Configuration EEPROM

The card has a Raspberry Pi Model B+ configuration EEPROM.

3.3V Connectors

The following are all 3.3VDC connections.

Raspberry Pi B Plus GPIO Connector J8 on the Pi.

Bplus-gpio-edited.png

I2C bus

GND 3.3V SDA SCL

UART I/F

GND 3.3V TxD RxD

IO_4 GVS

GND 3.3V GPIO_4

IO_18 GVS

GND 3.3V GPIO_18

IO_17 GVS

GND 3.3V GPIO_17

IO_27 GVS

GND 3.3V GPIO_27

IO_23 GVS

GND 3.3V GPIO_23

IO_22 GVS

GND 3.3V GPIO_22

IO_24 GVS

GND 3.3V GPIO_24

IO_25 GVS

GND 3.3V GPIO_25

SPI0 (Serial Peripheral Interface)

GND 3.3V MOSI MISO SCK CE0

SPI1 (Serial Peripheral Interface)

GND 3.3V MOSI MISO SCK CE1

IO_5 GVS

GND 3.3V GPIO_5

IO_6 GVS

GND 3.3V GPIO_6

IO_12 GVS

GND 3.3V GPIO_12

IO_13 GVS

GND 3.3V GPIO_13

IO_19 GVS

GND 3.3V GPIO_19

IO_16 GVS

GND 3.3V GPIO_16

IO_26 GVS

GND 3.3V GPIO_26

IO_20 GVS

GND 3.3V GPIO_20

IO_21 GVS

GND 3.3V GPIO_21

J22 - EEPROM Address/Write Enable Header - Rev X2 Hat

Write Enable - Install header to allow writes to EEPROM Remove header to protect EEPROM contents from accidental writes

J23 - Voltage translator, 3V side

V3-0 = Bit 1 V3-1 = Bit 2 V3-2 = Bit 3 V3-3 = Bit 4 V3-4 = Bit 5 V3-5 = Bit 6 V3-6 = Bit 7 V3-7 = Bit 8 V3-8 = Bit 9 V3-9 = Bit 10 V3-A = Bit 11 V3-B = Bit 12 V3-C = Bit 13 V3-D = Bit 14 V3-E = Bit 15 V3-F = Bit 16

5V Connectors

The following are 5V connectors.

V5-0 - GVS connector, 5V side Ground +5V Bit0 V5-1 - GVS connector, 5V side Ground +5V Bit1 V5-2 - GVS connector, 5V side Ground +5V Bit2 V5-3 - GVS connector, 5V side Ground +5V Bit3 V5-4 - GVS connector, 5V side Ground +5V Bit4 V5-5 - GVS connector, 5V side Ground +5V Bit5 V5-6 - GVS connector, 5V side Ground +5V Bit6 V5-7 - GVS connector, 5V side Ground +5V Bit7 V5-8 - GVS connector, 5V side Ground +5V Bit8 V5-9 - GVS connector, 5V side Ground +5V Bit9 V5-A - GVS connector, 5V side Ground +5V Bit10 V5-B - GVS connector, 5V side Ground +5V Bit11 V5-C - GVS connector, 5V side Ground +5V Bit12 V5-D - GVS connector, 5V side Ground +5V Bit13 V5-E - GVS connector, 5V side Ground +5V Bit14 V5-F - GVS connector, 5V side Ground +5V Bit15

Layout

Kickstarter Edition

RPP-UIO-16-X2-CAD.PNG

Design Validation Testing - Rev X1 Board

RASPI-PLUS-GVS-CFG DVT

Factory Acceptance Tests (FAT)

Hardware

FAT requires the following:

Raspberry Pi Model B+ or equivalent (RasPi) Power supply for Raspberry Pi (5V at 1 Amp min) with Micro USB connector Monitor, Keyboard or Ethernet cable and laptop running puTTY Test Software loaded onto RasPi (2) LED-Test card Cable set Unit Under Test (UUT) Preliminary Install UUT onto RasPi Install Cables Power up card Log into RasPi pi raspberry

I2C

Install WE jumper cd ~/RasPi/RPP-UIO-16/eeprom/ sudo ./eep2flash.sh -w -t=24c32 -f=eepcfg.eep sudo ./eep2flash.sh -r -t=24c32 -f=myeep.eep rm stuff.eep ./eepdump myeep.eep stuff.eep more stuff.eep | grep vendor more stuff.eep | grep "product "

Verify: vendor "land-boards.com" # length=15 product "RPP-UIO-16" # length=10 Remove WE jumper cd ~/RasPi/RPP-UIO-16/eeprom/ sudo ./eep2flash.sh -w -t=24c32 -f=eepcfg.eep

Verify Writing... dd: writing `/sys/class/i2c-adapter/i2c-0/0-0050/eeprom': Connection timed out 0+1 records in 0+0 records out 0 bytes (0 B) copied, 0.0564552 s, 0.0 kB/s Error doing I/O operation. Ctrl-C to halt

GVS Connector - Blink LEDs Tests On RasPi console: cd ~/RasPi/RPP-UIO-16/ sudo python blinkLEDs-RPP-UIO-16.py

LEDs should cycle Combined Copy/paste cd ~/RasPi/RPP-UIO-16/eeprom/ sudo ./eep2flash.sh -w -t=24c32 -f=eepcfg.eep sudo ./eep2flash.sh -r -t=24c32 -f=myeep.eep rm stuff.eep ./eepdump myeep.eep stuff.eep more stuff.eep | grep vendor more stuff.eep | grep "product "

cd ~/RasPi/RPP-UIO-16/eeprom/ sudo ./eep2flash.sh -w -t=24c32 -f=eepcfg.eep

cd ~/RasPi/RPP-UIO-16/ sudo python blinkLEDs-RPP-UIO-16.py

Assembly Sheet

• RPP-UIO-16 Rev X2 Assembly Sheet