Setting up the GAP8 SDK

|Setting up the GAP8 SDK
Setting up the GAP8 SDK2019-09-23T13:38:53+00:00

Setting up the GAP8 SDK


The GAP8 SDK allows you to compile and execute applications on the GAP8 IoT Application Processor. This SDK is an extract of the necessary elements from the pulp-sdk ( produced by the PULP project, to provide a development environment for the GAP8 series processors.

We provide you with all the necessary tools and two different operating systems for GAP8:

  • Tools

    • GAP8 RISCV GNU toolchain: a pre-compiled toolchain inherited from RISC V project with support for our extensions to the RISC-V Instruction Set Architecture.
    • PLPBRIDGE: a tool from the PULP project which allows communication between your PC and a GAP8 processor. Using this tool you can:
      • Program / control GAP8
      • Debug your application using GDB
      • Program the GAPuino flash memory with applications
  • Operating Systems

    • PULP OS - The open source embedded RTOS produced by the PULP project
    • Arm® Mbed™ OS - Arm Mbed OS is an open source embedded operating system. GreenWaves Technologies has ported it to GAP8 and VEGA.
    • FreeRTOS - FreeRTOS is an open source real time operating system. GreenWaves Technologies has ported it to GAP8
    • PMSIS - PMSIS is an open-source system layer which any operating system can implement to provide a common API to applications. We currently provide it fro PULP OS and FreeRTOS, and it is used by our applications to be portable.

Getting started with the GAP SDK

These instructions were developed using a fresh Ubuntu 16.04 Xenial 64-Bit virtual machine from

The following packages needed to be installed:

sudo apt-get install -y build-essential git libftdi-dev libftdi1 doxygen python3-pip libsdl2-dev curl cmake libusb-1.0-0-dev scons gtkwave libsndfile1-dev
sudo ln -s /usr/bin/libftdi-config /usr/bin/libftdi1-config

The precompiled toolchain should be clone by using git lfs, this should be installed by using the following command:

curl -s | sudo bash
sudo apt-get install git-lfs
git lfs install

Our modules requires a few additional Python packages that you can install with this command:

pip3 install -r requirements.txt

In order to use the Gap tools for neural networks (nntool), we strongly encourage to install the Anaconda distribution. You can find more information here:

Once Anaconda is installed, you need to activate it and install python modules for this tool with this command:

pip install -r tools/nntool/requirements.txt
pip install -r requirements.txt

Configure USB Port for GAPuino Evaluation Board and Gapoc board

For the USB serial connection our GAPuino and Gapoc boards use an FDDI 2 port serial to USB controller. This needs to be set up (the driver is installed in the apt-get install step above).

Add your username to the dialout group:

sudo usermod -a -G dialout <username>

Logout from your session and login again. Now create a udev rule for gapuino ftdi2232 usb chip

touch 90-ftdi_gapuino.rules
echo 'ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6010", MODE="0666", GROUP="dialout"'> 90-ftdi_gapuino.rules
echo 'ATTRS{idVendor}=="15ba", ATTRS{idProduct}=="002b", MODE="0666", GROUP="dialout"'>> 90-ftdi_gapuino.rules
sudo mv 90-ftdi_gapuino.rules /etc/udev/rules.d/
sudo udevadm control --reload-rules && sudo udevadm trigger

If you are using a Virtual Machine make sure that you give control of the FTDI device to your virtual machine. Plug the GAPuino into your USB port and then allow the virtual machine to access it. For example, for VirtualBox go to Devices->USB and select the device.

Please also make sure that your Virtual Machine USB emulation matches your PC USB version. A mismatch causes the USB interface to be very slow.

The following instructions assume that you install the GAP SDK into your home directory. If you want to put it somewhere else then please modify them accordingly.

Download and install the toolchain:

Now clone the GAP8 SDK and the GAP8/RISC-V toolchain:

git clone
git lfs clone

Install the toolchain:

cd ~/gap_riscv_toolchain

Initialize and download all the sub projects of the SDK:

cd ~/gap_sdk
git submodule update --init --recursive

Configure the SDK:

You need to source the appropriate config file for the board that you have. The SDK supports 2 boards (gapuino and gapoc) and each of them can use version 1 or version 2 of the GAP8 chip. Boards bought before 10/2019 contains GAP8 version 1 and use a USB B plug for JTAG while the ones bought after contains version 2 and use a USB micro B for JTAG.

Hereafter you can find a summary of the available boards and their configuration file.

Board | Chip | Config file |:-------:|:----------:|:----------------------:| Gapuino | GAP8 v1 | configs/ Gapuino | GAP8 v2 | configs/ Gapoc | GAP8 v1 | configs/ Gapoc | GAP8 v2 | configs/

Once the proper config file is sourced, you can proceed with the SDK build.

Note that after the SDK has been built, you can source another config file to change the configuration. In this case the SDK will have to be built again. As soon as the SDK has been built once for a configuration, it does not need to be built again for this configuration, unless the SDK is cleaned.

Build the SDK:

You can build the SDK with this command:

make all

GVSOC virtual platform will be installed during the previous build.

Getting the Autotiler

The autotiler code generation library needs to be downloaded by this following commands:

cd ~/gap_sdk/
make autotiler

During the download, you will be asked several simple questions and then you will receive an email with an URL. Please copy the url in the mail to the last question, then the download and installation would be started automatically. If you have already answered these questions, this enquiry will be skipped.

For offering you the best support, please answer the questions.

Getting nntool

You first need to install Anaconda and Python dependencies (see above).

Then execute:

cd ~/gap_sdk/
make nntool

Compiling, running and debugging programs

The following command configures the shell environment correctly for the GAP8 SDK. It must be done for each terminal session:

source ~/gap_sdk/configs/

The configuration file you should sourced may be different, depending on the board you are using (see above).

Tip: You can add an "alias" command as following in your .bashrc file:

alias GAP_SDK='cd ~/gap_sdk && source'

Typing GAP_SDK will now change to the gap_sdk directory and execute the source command.

Finally try a test project. First connect your GAPuino to your PCs USB port and then type:

cd ~/gap_sdk/examples/pulp-examples/helloworld
make clean all run

After the build you should see:

Entering main controller
Entering cluster on core 0
There are 8 cores available here.
[clusterID: 0x 0] Hello from core 0
[clusterID: 0x 0] Hello from core 1
[clusterID: 0x 0] Hello from core 2
[clusterID: 0x 0] Hello from core 3
[clusterID: 0x 0] Hello from core 4
[clusterID: 0x 0] Hello from core 5
[clusterID: 0x 0] Hello from core 6
[clusterID: 0x 0] Hello from core 7
Leaving cluster on core 0
[clusterID: 0x20] Hello from core 0
Test success: Leaving main controller
Detected end of application, exiting with status: 0

Debugging Programs

The JTAG bridge allows for printf's in your code to generate messages on your PC. GAP8 also has support for gdb server over JTAG for both pulp-os and mbed-os programs.

To enable gdbserver run mode execute the make target gdbserver:

make clean all gdbserver

The program will load and gdbserver will be started. Connect to the target with gdb from another shell (remember to source the file in the root of the SDK in your new shell). Change directory to the directory containing your test program and then:

riscv32-unknown-elf-gdb BUILD/GAP8/GCC_RISCV/test

Once gdb has loaded connect to the gdbserver on the target.

(gdb) target remote localhost:1234
Remote debugging using localhost:1234

Using the flasher (Hyperflash)

Add the following line into your application Makefile:

PLPBRIDGE_FLAGS += -f <file1> <file2> <file3> ......

Without any further options the files are flashed but your application is not executed.

If you want to execute your application after flashing use the following options:

If you want to boot your application from jtag:


If you wan to boot your application from hyperflash:


These two flags cannot be used at the same time.

If you choose to boot your application from HyperFlash, and you want to view the output of printf's in your code then you can use a terminal program, like "cutecom":

sudo apt-get install -y cutecom

Then please configure your terminal program to use /dev/ttyUSB1 with a 115200 baud rate, 8 data bits and 1 stop bit.

Using the file IO

Through our new bridge tool (pulp-rt-bridge), you could load/store from/to in your PC. For example, if you want to use an image locally, but run the algorithm with this image on GAP8. You could use this functionality to do it.

To trigger this function in bridge, you need to add this flag in your Makefile:

PLPBRIDGE_FLAGS += -fileIO <option>

The option should be a number, which would be used for let the bridge wait for \<option> seconds. Because of the synchronization between this bridge and our debug bridge, we need to wait until the program has been load and executed on GAP8. If you don't put a number, the default value is 2 (seconds).

Otherwise, you could run this service manually:

In another terminal:

Configure the environment, and then:

plpbridge-rt --binary=<path of your binary file> --chip=gap

Please read the example for more information: examples/pulp-examples/kernel/bridge

For your information, this new bridge is quite slow, please be patient when you are using it. We will resolve this problem as soon as possible.


Build the documentation:

cd gap_sdk
make docs

If you haven't download and install the autotiler, you will probably have some warnings when you build the docs. All the documentations are available on our website:

You can read the documentation by opening gap_doc.html in the docs folder in your browser:

firefox docs/gap_doc.html

If you would like PDF versions of the reference manuals you can do:

cd docs
make pdf

Upgrading/Downgrading the SDK

If you want to upgrade/downgrade your SDK to a new/old version:

cd gap_sdk
git checkout master && git pull
git checkout <release tag name>
git submodule update --init --recursive
make clean all

Please check our release tags here to ensure the version:

Getting help

Please log any issues you have with the SDK in the github project.

We have also created a GAP8 developers’ forum for you to ask questions and find out more about the GAP8 SDK. You can join this group at


Arm® Mbed™ OS are registered trademarks or trademarks of Arm Limited (or its subsidiaries) in the US and/or elsewhere.