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Instant DIY controller project plans Linux add-on

Sep 5, 2014 — by Eric Brown — 1,730 views

The “PIEP” Kickstarter project offers a snap-together, modular, DIY control system with a wide range of processor and I/O boards, and a future Linux option.

E3 Embedded Systems built its “Processor Independent Embedded Platform” (aka PIEP) kit to showcase its various microcontroller unit (MCU) and peripheral boards. The modular development kit not only offers a choice of MCU boards, but let’s you choose among 21 peripheral boards, with more on the way. The stackable design enables up to 36 peripherals modules to fit on one motherboard.

PIEP setup (left), and kit with motherboard, processor cards, expansion modules
(click images to enlarge)

The PIEP project has until Sept. 24 on Kickstarter to meet its $70,000 goal. The modular kit starts at $140, in a package due in March 2015. This gives you a motherboard, an ATMegaX processor board, and three peripherals. A $200 early bird package lets you choose between ARM, PIC, and Freescale MCUs and gets the kit to you by January. Other packages range up to a full $950 early bird kit with three processor boards and all 21 peripherals.

Inside PIEP

The initial PIEP implementation lets you plug one of three E3-built processor boards into the motherboard via a high density 200-pin connector: an Atmel SAM3X (Cortex-M3), an AVR ATMegaX (PIC), or a Freescale MC9S12 computer-on-module (COM). The processor interface is said to support 8-, 16-, or 32-bit processor architectures.

PIEP motherboard, top and bottom
(click image to enlarge)

The 4.35 x 4.03-inch motherboard provides 12 headers (six on each side of the board), called “Stackable Peripheral Interface Ports” (aka SPIPs), where you can stack up to three 1.25 x 1.25-inch PIEP expansion modules for a grand total of up to 36 expansion modules per system. The PIEP motherboard has an input voltage range of 9 to 24 Volts DC, unregulated, and supports both JTAG-20 and 6-pin BDM/ICD debuggers and programmers.

PIEP processor board top (Atmel version) and bottom (Freescale version)
(click images to enlarge)

Where’s the Linux?

If microcontrollers (MCUs) don’t get you going, you should know that on Sept. 3, E3 announced it would add a Linux-ready processor in 2015, once the current set of products is completed. According to an email response from E3 cofounders Chad DeMeyers and Kevin Huffman, the Linux-ready option “will almost certainly be in the form of an adapter to permit an existing commercial product to work with our platform.”

One option would be a DAQ-oriented board with a Linux-ready processor such as the 400MHz, ARM9-based Atmel SAM9X25, one of the AT91SAM9X5 family of system-on-chips, along with “the resources needed to support our peripherals,” write DeMeyers and Huffman. An alternate approach would be to implement a board without DAQ-style resources, such as the Raspberry Pi Compute Module, and offer port adapters to create the needed resources, they add.

Raspberry Pi
Compute Module

(click to enlarge)

For a Pi-based system, “the motherboard would contain mostly communications type interface ports (I2C, SPI, etc),” write DeMeyers and Huffman. “An adapter could be attached to a port to create a virtual port with the needed resources; peripherals stacked atop the virtual port peripheral card would then have access to resources needed for implementation (such as PWM),” they continue. “A good example of how this works can be found in our SPI to SCI port adapter. This peripheral plugs into a SPI port and presents a SCI type port to peripherals stacked on top of the card.”

“If you are a Linux champion, we’d love to hear your ideas,” write DeMeyers and Huffman.

More about PIEP’s expansion modules

Functions added modularly via the motherboard’s SPIP headers are “generally categorized by” I2C (2x), SPI (2x), SCI (2x) or digital (6x), with the latter mostly integrating resources common across all PIEP compatible processors, says E3. Digital SPIP headers 4 to 6 are said to contain mostly processor specific resources.

PIEP with stacked peripheral boards (left) and PIEP-based robot prototype
(click images to enlarge)

Although each SPIP header can deliver up to 1A current to its three-module stack, the maximum total current available for all SPIPs in a system is 2A, notes the project. If needed, expansion modules can be made larger, so they occupy two, four, or all six locations on the top or bottom of the PIEP motherboard. (Presumably larger-sized expansion modules could still allow additional modules to stack above them.)

PIEP expansion modules can also be remotely mounted, using a PIEP Remote Mount Kit. The boards are about 1.25 x 1.25 inches and are powered at 3.3V or 5V via jumpers. Interfaces to external devices use 1mm JST (DPIP) or 2mm (peripheral) connectors.

The following are the 21 currently available peripheral boards for the PIEP:

  • 3-Digit Numerical Display — for numeric feedback
  • Accelerometer — with digital and analog modes
  • Arduino Shield Adapter — allows use of Arduino shields in PIEP systems, and PIEP peripheral modules in Arduino systems
  • Breakout — versatile peripheral compatible with all SPIP headers and voltages
  • Buzzer — audible feedback
  • CAN Bus Driver — high speed, reliable communications
  • Digital Port Expander — creates two 8-bit GPIO ports with interrupt
  • Digital to Analog Converter — 2-channel, 12-bit
  • EEPROM — I2C-based, operating at either 3.3V or 5V
  • H-Bridge — double-wide driving two servo or one stepper motor (24V/ 2Amps max.)
  • Motion Sensor — IR-based with a 5-meter range
  • Real Time Date/Clock — I2C-based with an onboard lithium battery backup
  • Relay — offers two small signal relays, each for single pole, double throw
  • SCI to RS232 — converts TTL level serial signals to RS232
  • SCI to USB — adds USB
  • SPI to SCI — adds SCI port from SPI resources using MAX3100 chip
  • Switch & LED — user control and feedback with 4x momentary switches and 4x visual indicators
  • Temp/RH — measures up to -40 to 85°C and 0 to 100% relative humidity
  • Terminal — useful for debugging, testing, and external signal interfaces
  • Thermocouple — for high temperature measurements (optimized for 25 to 100°C, supports 0 to 400°C)
  • Remote Mount Kit — 2x breakouts and an interconnect cable

Many of the PIEP peripheral modules are shown at this page of E3’s website.

Kickstarter project stretch goals, demo video

Stretch goals for the project, in addition to the upcoming Linux option, include:

  • Smaller 2 x 4-inch motherboard with fewer peripherals
  • BeagleBone adapter, similar to the Arduino Shield Adapter
  • Tiny Circuits adapter, similar to the Arduino Shield Adapter
  • LCD display
  • Flash memory
  • Ethernet adapter

The E3 website linked to below offers schematics and extensive documentation for all the PIEP board components. There’s no mention of open source licensing, however.

PIEP demo

Further information

The PIEP kit is available in various Kickstarter funding packages through Sept. 24, ranging from $140 to $950 with shipments due in January or March, depending on the package. More information may be found at the PIEP Kickstarter page and the E3 Embedded Systems website. The project’s plan to add a Linux processor option during 2015 was announced here.

— with additional reporting by Rick Lehrbaum

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