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BeagleWire - FPGA development cape for the BeagleBone

The BeagleWire is an FPGA development platform that has been designed for use with BeagleBone boards. BeagleWire is a cape on which there is an FPGA device - Lattice iCE40HX. The Lattice iCE40 is a family of FPGAs with a minimalistic architecture and very regular structure, designed for low-cost, high-volume consumer and system applications. The significance of FPGAs is continuously increasing, as they are more and more often used to support ARM processors. BeagleWire does not require external tools (JTAG) and the whole software is Open Source. iCE40 is an energy saving device, allowing to work with small batteries. FPGA cape allows easy and low cost start for beginners who would like to take their first steps in working with FPGAs. The developed software will be an easy and, at the same time, efficient tool for communication with FPGA. At this point FPGA will be able to meet the requirements of even more advanced applications. The BeagleWire creates a powerful and versatile digital cape for users to create their imaginative digital designs.

BeagleWire features:

  • FPGA: Lattice iCE40HX4K - TQFP 144 Package
  • GPMC port access from the BeagleBone
  • SPI programming port from the BeagleBone
  • 4 layer PCB optimized design to support maximum performance for high bandwidth applications
  • BeagleBoard optimized - compatible with BeagleBone Black, BeagleBone Black Wireless, element14 BeagleBone Black Industrial
  • does not require external tools (JTAG)
  • minimalistic architecture and very regular structure
  • energy saving device allows to work with small batteries
  • lower application costs
  • fully open-source toolchain

BeagleWire Peripherals:

  • 32 MB SDRAM
  • 100Mhz external clock
  • 4 LEDs
  • 4 PMOD connectors
  • 4 Grove connectors
  • 2 user push buttons
  • 2 input DIP switch

Software\Driver support

BeagleWire software support is still developing. A lot of useful examples and ready to use solutions can be found there. For communication between FPGA and ARM, GPMC can be used. This is an easy and efficient solution. BeagleWire software repository has special components for it. You can just map your logic in BeagleBone memory. A lot of examples have kernel driver e.g. SPI, GPIO. After preparing the FPGA device you can use it as a typical GPIO/SPI from user space. A part of examples do not belong to kernel subsystems e.g. rotary excoder, ultrasonic ranger sensor or blink leds. In these examples, you can connect to FPGA using write/read operation for /dev/mem file.


The project is the result of the community work and it is still under development. If you can support this project or if you have any questions, feel free to contact us.
Michael Welling
Patryk Mezydlo


BeagleWire KiCAD Repository
BeagleWire Software Repository
BeagleWire project page
BeagleWire project page
BeagleWire Schematic

User Manual

Board Diagram

Bw diagram.png

Expansion Ports, Interfaces and Peripherals

GPMC Communications interface

The general-purpose memory controller (GPMC) is a unified memory controller dedicated to interfacing external memory devices: SRAM-like memories and application-specific integrated circuit (ASIC) devices, asynchronous, synchronous, and page mode (only available in non-multiplexed mode) burst NOR flash devices, NAND Flash, Pseudo-SRAM devices. The GPMC bus enables a high bandwidth interface between the FPGA and the ARM processor. GPMC controller is configured from the DTS file. GPMC pins are brought out to BeagleBone P8/P9 headers. BeagleWire software repository contains a component written in Verilog which supports communication between FPGA and ARM.

SPI Programming interface

Programming is done by SPI interface. BeagleWire uses second BeagleBone SPI port. SPI frequency should be between 1Mhz and 25Mhz.

PMOD Expansion Ports

BeagleWire contains four Digilent Inc. Pmod ports. The Pmod standard has a lot of ready modules. Thanks to four Pmod ports we can use as many as 24 additional pins.


There are four blue LEDs.

DIP Switch

BeagleWire has two DIP switch. "ON" position is treated as logical zero.

Push Button

There are two user buttons. We used schmitt trigger, a simple structure which prevents buttons bouncing.

Additional common IRQ lines

Two lines are directly connecting BBB and BW. These lines do not have intended use. In many applications they are used as interrupt lines.

SDRAM Memory

BealgeWire has 32 MB SDRAM memory. BeagleWire software repository contains a simple SDRAM controller written in Verilog which supports communication between SDRAM and iCE40.

Grove Expansion Ports

BeagleWire contains four Grove connectors. First and second connectors are used as I2C. Other connectors have no destinations.

External clock source

BeagleWire has an external 100 Mhz clock generator. Clock speed can be changed using internal PLL.


More information about I/O connections can be found at:BeagleWire pcf file or BeagleWire Schematic

Connecting BeagleWire with BeagleBone (P8/P9 Connector Pin Usage)

Quick Start Guide

Use pre-prepared BBB image

Pre-prepared sd-card BBB image can be found here: BBB image The image contains all required drivers and scripts to start BeagleWire development.

Download image:

$ wget

Verify image:

$ sha256sum BeagleWire-image.tar.xz

Unpack image and write the image to the memory card (please check if you have the correct SD card device — in my case it is /dev/sdd):

$ tar xf BeagleWire-image.tar.xz
$ sudo dd if=image.img of=/dev/sdX

Programming the FPGA from the BeagleBone

Pre-prepared BBB image contains directory (/home/debian/load-fw) with required scripts, drivers and a simple blink example. Load bitstream to FPGA:

$ cd /home/debian/load-fw/
$ ./ blink.bin

To check how programming is proceeding, use:

$ dmesg

Results should look like this:

[ 2427.827170] Starting FPGA loader
[ 2427.830561] fpga_manager fpga0: writing blink.bin to Lattice iCE40 FPGA Manager
[ 2428.012162] Stopping FPGA loader

Synthesizing Verilog code using IceStorm toolchain

Prepare Verilog module for first FPGA programming

module top(input clk, output [3:0] led);

	reg [27:0] counter = 0;
	always @(posedge clk) counter <= counter + 1;

	assign led[0:3] = counter[24:27];

PCF file is used for connecting input/output module signals with physical pins in FPGA device.

set_io clk 61

set_io led[0] 28
set_io led[1] 29
set_io led[2] 31
set_io led[3] 32 


PROJ = blink
BUILD = ./out
FOOTPRNT = tq144:4k

SRC = top.v
SRC +=
PIN_SRC = pinmap.pcf

.PHONY: all load clean

        mkdir -p $(BUILD)
        yosys -q -p "synth_ice40 -top top -blif $(BUILD)/$(PROJ).blif" $(SRC)
        arachne-pnr -d $(DEVICE) -P $(FOOTPRNT) -p $(PIN_SRC) -o $(BUILD)/$(PROJ).asc $(BUILD)/$(PROJ).blif
        icepack $(BUILD)/$(PROJ).asc $(BUILD)/$(PROJ).bin
        echo -e "\x0\x0\x0\x0\x0\x0\x0" >> $(BUILD)/$(PROJ).bin

        sh /home/debian/load-fw/ $(BUILD)/$(PROJ).bin

        rm -rf ./$(BUILD)/

To build the above example:


To load bitstream to FPGA:

make load

Other Guides

Prepare BBB Image

Prepare a custom kernel image, an easy instruction on how to do it can be found here: BBB prepare image instruction. Attach(<M>) FPGA-mgr and iCE40-spi driver. Linux kernel should be version 4.12 or newer.

 Device Drivers ---> FPGA Configuration Support --->  <M> FPGA Configuration Framework 
                                                      <M>      Lattice iCE40 SPI   

Writing EEPROM configuration contents

BeagleWire cape has a EEPROM memory, so that the BBB device overlay is automatically loaded up on each boot up. EEPROM contents and loading script are located in BeagleWire software repository.
Check BW_EEPROM.bin content:

$ xxd  BW_EEPROM.bin

It should look like this:

00000000: aa55 33ee 4131 4265 6167 6c65 426f 6e65  .U3.A1BeagleBone
00000010: 2042 6561 676c 6557 6972 6543 6170 6500   BeagleWireCape.
00000020: 0000 0000 0000 3030 4130 6265 6167 6c65  ......00A0beagle
00000030: 626f 6172 642e 6f72 6700 4257 2d49 4345
00000040: 3430 4361 7065 0000 0000 3030 4257 5245  40Cape....00BWRE
00000050: 5630 3230 3137 0000 0000 0000 0000 0000  V02017..........

Load EEPROM using script:

$ sudo ./

Device Tree Overlay

Device Tree is required for enabling SPI and GPMC.
Install the DTS compiler:

$ wget -c
$ chmod +x
$ ./

Compile the dts file:

$ dtc -O dtb -o DTS/BW-ICE40Cape-00A0.dtbo -b 0 -@ DTS/BW-ICE40Cape-00A0.dts

Copy dtbo file to /lib/firmware on the BBB:

$ cp BW-ICE40Cape-00A0.dtbo /lib/firmware

Installing the IceStorm toolchain

Install toolchain on PC or BBB.
On PC:

$ sudo ./


$ sudo ./ BBB


BeagleWire software repository has a lot of different sources. The following description shows how to use it. Examples can be divided into two parts. The first part is the simplest examples which do not have their own subsystem in Linux kernel e.g. rotary excoder, ultrasonic ranger sensor or blink leds. In these examples we can connect with FPGA using write/read operations for /dev/mem file. The second part consists of examples with kernel driver e.g. SPI, GPIO.