AdvaBoard RPi1 - Raspberry Pi extension board

mechanics

• PCB-size: 96.5 * 64.8mm
• mounting holes:
  • for a Raspberry Pi Rev. 2
  • in all 4 corners (as generic mount, display-mount and/or fixation for a Raspberry Pis Rev. 1)
• weight: about 50g
• required power-supply: 5V, via 5V-power-supply-connector or via Raspberry Pi (switchable)

The AdvaBoard RPi1 an either be stacked directly above or below a Raspberry Pi, or mounted separately.

real-time clock / RTC

Unfortunately, the Raspberry Pi itself does not contain a real-time clock, so you usually have to either manually enter the current time and date or obtain them from the network (NTP) every time you boot your Raspberry Pi.

The AdvaBoard RPi1 solves this problem, by providing the Raspberry Pi with a (battery-backed) real-time clock. In addition, the real-time clock can be used to power-up the Raspberry Pi and the AdvaBoard on a certain time or in certain intervals (see power-supply / power-management), or to trigger some actions.

power-supply / power-management

The AdvaBoard RPi1 can

• either be powered from the Raspberry Pi and its Micro-USB-power-supply,
• or be powered from the 5V-power-supply-connector on the AdvaBoard, and then also power the Raspberry Pi

But there may always be only one of the two power supplies (5V-power-supply-connector on the AdvaBoard or power-supply on the Raspberry Pi), never both!

The 5V-power-supply-connector on the AdvaBoard should be preferred, since only then the AdvaBoard can turn the Raspberry Pi on and off. The power-management provides the following functions:

• switch the 5V-power-supply on and off (if an appropriate 5V supply is used)
• power-on of the 5V-power-supply at a certain time/on certain time intervals or when an I²C-interrupt occurs
• separately power-on/off the Raspberry Pi, E-SPI/RS-232/RS-485, CPLD and TFT-display by the integrated microcontroller at certain times or certain events
• battery-power for the real-time clock and selected I²C-sensors when the power-supply is switched off

Thereby, the AdvaBoard is perfectly suited for running from a larger battery or for self-contained operation with a solar panel, since the complete system (except the battery-powered real-time clock and maybe some I²C-sensors) can turn itself off, and wake up again depending on time or events. Directly after wakeup, the integrated microcontroller works and can e.g. poll some sensors and turn on additional components or the Raspberry Pi when needed.

To wake the AdvaBoard up, you can use a simple button, I²C-sensors with interrupt-output or an I²C-board including a microcontroller, which e.g. monitors some sensors.

5V-power-supply

Connector: PCB connector, 3 pins, pitch 2.54mm

5V-power-supply jack (male)

(mating view)

pin	signal	description
1	+5V	power-supply-input, 5V
2	GND	ground
3	PWR_ON	power-on/off control-line (low=on, high=off)

battery

Connector: PCB connector, 2 pins, pitch 2.54mm

battery jack (male)

(mating view)

pin	signal	description
1	+VBATT	battery-input, about +3V
2	GND	ground

Raspberry Pi-connector

A 26-way ribbon cable is used to connect the AdvaBoard RPi1 with the Raspberry Pi.

Connector: IDC header, 26 pins, pitch 2.54mm

Raspberry Pi jack (male)

(mating view)

I²C / SMBus

The I²C-bus is by now the interface for digital sensors, e.g. for temperature-sensors, temperature-/humidity-sensors, acceleration-sensors, motion detectors etc.

The AdvaBoard here uses:

• 3.3V supply voltage
• 3.3V levels (not 5V-tolerant!)
• a separate wire for battery-power
• an interrupt-wire for fast response times and for waking up the AdvaBoard/Raspberry Pi on certain events

The pinout was thereby chosen in a way to minimize the crosstalk between SDA, SCL and the interrupt wire.

Connector: IDC header, 6 pins, pitch 2.54mm

I2C jack (male)

(mating view)

E-SPI

The SPI-interface offers a simple and very fast serial bus. It's especially suited for periphery which needs a high data rate or low latency, e.g. external CPLDs/FPGAs, displays etc.

The AdvaBoard here uses:

• 5V supply voltage
• 3.3V level, 5V-tolerant
• 4 additional address-wires
• an optional interrupt

The additional address-wires can either be used as normal chip-selects to altogether select 5 SPI-devices, or to select up to 16 devices with additional address-decoders. So, the "E-SPI" is perfectly suited to easily connect up to 16 external boards with ribbon cables to the AdvaBoard.

The address decoders can also include an interrupt logic, enabling the SPI-slaves to trigger interrupts (without any additional wires).

Connector: IDC header, 10 pins, pitch 2.54mm

E-SPI jack (male)

(mating view)

digital-I/O / analog-I/O

The AdvaBoard includes several analog- and digital-I/Os:

• 8 digital-I/Os via CPLD with optional hardware-supported processing (e.g. for 2-phase-counters)
• 2 digital-I/Os via microcontroller incl. PWM, counter/timer, ...
• 4 analog-inputs (16 bit, 1 ksps) incl. voltage divider and filter
• 2 analog-outputs (8 bit, 0..0.25/0.5/1/2mA, max. 2.0V),
  alternatively usable as digital-I/Os

Connector: IDC header, 20 pins, pitch 2.54mm

I/O jack (male)

(mating view)

RS-485 / EIA-485

The RS-485-interface is a robust and interference-proof industrial interface, which can be used to connect several devices (partly with hubs), and which is also suited for longer distances.

In addition to the RS-485-interface, the AdvaBoard also contains a RS-485-terminator, which can be activated/deactivated by a jumper. Furthermore, it's possible to use an automatic bit-modification to address the devices, which is e.g. necessary for the Advamation-RS-485-protocol.

Connector: PCB-connector, 4 pins, pitch 2.54mm

RS-485 jack (male)

(mating view)

RS-232 TTL

The integrated RS-232-interface with TTL-levels can be used to connect various periphery, like e.g. a GPS or a radio module.

There's also a level-shifter available, which converts this interface to a normal RS-232-interface (with DB-9 female jack), and a USB-RS-232-adaptercable to connect this interface to USB.

Connector: PCB-connector, 5 pins, pitch 2.54mm

RS-232 jack (male)

(mating view)

TFT-display-interface

The AdvaBoard contains an interface incl. controlling logic for digital TFT-displays. These displays can either be directly plugged/stacked on the AdvaBoard (and mounted to it), or connected to it with a ribbon cable and mounted separately.

There are currently TFT-displays available in the sizes 3.2" (320× 240), 4.3" (480×272), 5" (800×480) and 7" (800×480) -- all including a resistive touchscreen. The displays are fixed to a PCB which contains mounting holes, so the displays can be mounted to a front panel. Additionally, all displays contain a SD-card-slot.

Since the displays are controlled without using the Raspberry-Pi graphics chip, they are not intended for playing video or similar, but rather for graphical user interfaces (GUI) or as interactive data-display. However, framerates up to 50 fps (nearly 4 MPixel/s) can be achieved with the 3.2" display.

The display can be controlled both by the Raspberry Pi and the microcontroller of the AdvaBoard (e.g. to display a startup-screen). A framebuffer-driver, to use the display as default Linux-display (incl. X11), is also available.

In the future, it will be possible to connect additional TFT-displays to the AdvaBoard RPi1 via E-SPI.

For special applications, and when using an adapted version of the AdvaBoard and a special CPLD-firmware, it would even be possible to use the display-interface-pins as generic CPLD-I/Os (incl. hardware-supported processing by the CPLD).

Connector: IDC header, 40 pins, pitch 2.54mm

TFT-display jack (female)

(mating view)

JTAG/C2-output

The AdvaBoard includes a JTAG- and a C2-output, which can be used to program Xilinx CPLDs/FPGAs and SiLabs C8051-microcontrollers. So, you don't need a separate programmer for external Xilinx-CPLD- or SiLabs-microcontroller-boards.

It's also possible to use these interfaces to update the AdvaBoard-firmware, e.g. to add further functionality later or to adapt the AdvaBoard to special applications.