The Institute of Embedded Systems (InES)High Performance Multimedia group generated a low latency version of the classic Jamulus music rehearsal application for the Raspberry Pi 4
The classic Jamulus is an open source application for music groups who want to rehearse over the internet. Especially with the global pandemic, Jamulus is a great solution for bands and choirs to rehearse from home. With the Jamulus-Direct solution, the Institute of Embedded Systems reduces the latency of the audio connection compared to the classic Jamulus. The low audio latency is achieved through multiple peer-to-peer connections. This means that each participant is connected to the other members of the group via a dedicated connection. The audio no longer needs to be sent via an audio server, which reduces the latency.
Peer-to-Peer communication in Jamulus Direct reduces latency
The figure below shows the audio transmission in a classical server based session with three clients. Three computers run a client software. Computer 0 starts a client and a server. Each client sends their own audio to the server. The audio is mixed together at the server and sent back to the clients. However, the server topology shown below introduces latency because all data has to make a detour over the server.
Therefore, in Jamulus direct, a peer-to-peer topology eliminates the detour via the server (see figure below). Each participant in a peer-to-peer system exchanges its data with each other participant. Peer-to-peer is therefore the preferred structure to achieve the lowest possible latency.
This setup ensures the lowest possible latency between each device. To achieve low latency, a few challenges had to be mastered to get a well functioning system. For instance, that peer to peer connections usually are blocked by the firewall of the network router and therefore need a mechanism to open these ports on the firewall. A further issue is the management of the session. In server based systems, the server usually manages the session. It is the contact point for new clients to register to join the session and also to unregister when leaving. The peer-to-peer audio transmission showed audio latencies under 30 milliseconds for two locations, with a ping time of 13 milliseconds. A detailed paper of Jamulus Direct can be downloaded here.
Jamulus-Direct is written for the Raspberry Pi 4 and achieves high quality audio utilizing a USB audio card connected via the RPI4 USB interface. Every audio card with available Linux drivers is suitable (Tested with Focusrite Scarlet 2i2 and Behringer U-Phoria UM2)
The Institute of Embedded Systems (InES) at ZHAW, with great experience in hardware development for NVIDIA computing modules, developed a rapid prototyping system for the NVIDIA Xavier AGX.
To shorten the time to market, the prototyping system consists of a greatly reduced motherboard that can be equipped with different types of M2-footprint modules to add functions like HDMI in and out, FPD-Link III in and out, USB-c etc.
Due to the modular architecture, the user may configure a personalized system by adding from a choice of different modules. Due to the low complexity and flexibility of the provided interfaces, more custom-made modules can easily be developed.
The system consists of a minimal mother board, which only includes the necessary circuitry to startup and program the Xavier.
To keep size and costs low, the main board includes USB 2.0, HDMI and one 16-lane PCIe standard card slot. All other interfaces are provided by nine PCIe M2-footprint sockets which share not only PCIe lines, but also dedicated Xavier-AGX interfaces like MIPI- CSI, USB and I2C. An overview of possible configurations and currently available devices is given in the table below.
The Video-Out socket provides two HDMI or DisplayPort lines, as well as the required I2C lines. It is also possible to configure one DisplayPort and one HDMI output. This slot also carries USB2.0, if the user wants to implement HD-BaseT.
The USB socket allows two USB interfaces with USB connectors of choice (USB-A-B-C, USB on the go) I2C, CAN-Bus and serial UART are also supported.
Video-In Module 1 and 2 each support 2 CSI ports with 4 lanes or 4 CSI ports with 2 lanes which allows connecting 4k cameras or HDMI to CSI converters
The Network Module allows the connection of 1GBIT Ethernet over RGMII or another PCIe lane for PCIe high speed PHYs
For more information, availability and pricing, please see contacts on the right.
The ZHAW Institute of Embedded Systems (InES), High Performance Multimedia Group, developed a 4k video for Linux driver for the Lontium LT6911UXC HDMI to MIPI CSI-2 converter IC. The driver was written for NVIDIA Jetson Processors and enables the following features of the LT6911UXC
Supports 4k HDMI 2.0 to MIPI CSI-2, requiring only one CSI port
Up to 4k resolution
Only 4 CSI lanes (one port) are required to receive 4k@30fps
Converts 4:2:2 YcBCr to CSI-2 YUV streams 1)
Converts RGB to RGB CSI-2 streams 1)
A driver for the advanced LT6911GX with HDMI 2.1 support and 4k@60fps on a single CSI-2 port is in the pipeline at InES-HPMM group.
The complexity of today’s multiprocessor System-on-Chip (MPSoC) can lead to major security risks in embedded designs, as the available security functions are often not or insufficiently utilized.
InES (Institute of Embedded Systems at ZHAW) developed a reference design which demonstrates a concept of a secure boot implementation and runtime system on a Xilinx Zynq Ultrascale+.
The security concept includes dedicated on-chip security features like AES, RSA and hashing core. The reference design also describes how to implement a voltage and temperature tamper detection. In addition, secure key storage and various methods to minimize key usage are provided. The demonstrator implements the ARM Trust Zone technology with OP-TEE as a secure operating system.
Implementation examples and usage description of the Linux Crypto-API, using the dedicated cryptographic cores, are also included in the documentation.
The modular open-source reference design is provided on GitHub, which contains implementation examples for all the above features.
Please find the link to our secure boot reference design here:
The Institute of Embedded Systems at ZHAW developed a driver for the deserializer DS90UB954 and serializer DS90UB953 from Texas Instruments. The driver was tested on the RaspberryPi 4, NVIDIA Nano and NVIDIA Xavier modules.
FPD-Link III is a cost-effective solution for high speed video transmission. The video data, the bidirectional configuration signal and the power supply are all transmitted over a single coaxial cable. At the length of up to 15 m the coaxial cable can support data rates of 6 Gbps.
In order to use our FDP-Link III driver (link driver) on different hardware, the driver was designed to be highly configurable. Additionally, the driver can be used with various FPD-Link III cameras. Instead of integrating the FPD-Link III part into already existing camera sensor drivers, the link driver is standalone and creates a transparent CSI and I2C link to the data source. This means that after the driver has set up the FPD-Link III connection, the sensor driver can be used without modifications.
The following figure shows an example of a sensor driver which controls a camera sensor directly over I2C and configures the video interface
Adding an FDP-Link III connection means that the I2C interface and the video channel will be routed through the coaxial cable. The deserializer and serializer are responsible for the conversion and forwarding of I2C and video data. The following figure shows the link driver configuring the deserializer and serializer over I2C. Once the setup is done, the sensor driver can configure the camera sensor over the I2C interface. Since the link is transparent, no changes have to be made to the sensor driver.
Configurability of the Driver
The following configurations can be done in the device tree: – I2C address of deserializer/serializer – Number of MIPI CSI lanes (the camera sensor and the hardware do not need to have the same number of lanes) – MIPI CSI lane speed – Enable/disable continuous clock – Enable/disable test pattern of deserializer/serializer – Virtual channel ID mapping – Configure GPIOs of deserializer/serializer – Set I2C alias addresses
The Institute of Embedded Systems at ZHAW has developed an open source adapter which allows streaming of a CSI-2 Camera interface to a Raspberry Pi. This allows connecting cameras with CSI interface via a long distance cable (up to 15m) to the CSI-2 input of a Raspberry Pi.
The long range adapter uses FPD-Link III high-speed video transmission technology by utilizing the existing MIPI CSI-2 interfaces of cameras and Raspberry Pi. A deserializer converts the FPD-Link III signal to CSI, is based on the DS90UB954 from Texas Instruments (TI). The counterpart located at the Raspberry Pi camera is based on the serializer DS90UB953 from TI. With these two components it is possible to transmit high-speed video data over a single coaxial cable which can be up to 15 meters long. Another advantage of FPD-Link III is the power over coax (PoC) capability, which transmits the power required for the camera sensor directly from the Raspberry Pi. The schematics and PCB designs are open source and available here. A driver for the Texas Instruments DS90UB95x serializer and deserializer can be found in our blog Linux Driver for TI DS90UB95x FPD-Link III serializer and deserializer
Institute of Embedded Systems Zurich University of Applied Sciences Zurich, Switzerland email@example.com
One third of food produced in the world for human consumption – approximately 1.3 billion tons – is lost or wasted every year. By classifying food waste of individual consumers and raising awareness of the measures, avoidable food waste can be significantly reduced. In this research, we use deep learning to classify food waste in half a million images captured by cameras installed on top of food waste bins. We specifically designed a deep neural network that classifies food waste for every time food waste is thrown in the waste bins. Our method presents how deep learning networks can be tailored to best learn from available training data.
In this paper, a more informative view to food waste production behavior at the consumption stage is achieved through classifying food waste in waste bins. The classification task is feasible by processing images captured from food waste in the waste bins. The images are captured by installing cameras on top of the waste bins and monitoring the top surfaces of food waste in the bins. This study focuses on classifying food waste in half a million images captured by cameras installed on top of waste bins. The system design of a smart garbage systems that uses our classification is out of the scope of this study.
The automatic classification of food waste in waste bins is technically a difficult computer vision task for the following reasons. a) It is visually hard to differentiate between edible and not-edible food waste. As an example consider distinguishing between eggs and empty eggshells.
b) Same food classes come in a wide variety of textures and colors if cooked or processed. c) Liquid food waste, e.g. soups and stews, and soft food waste, e.g. chopped vegetables and salads, can largely hide and cover visual features of other food classes.
In this research, we adopt a deep convolutional neural network approach for classifying food waste in waste bins. Deep convolutional neural networks are supervised machine learning algorithms that are able to perform complicated tasks on images, videos, sound, text, etc. The deep neural networks are composed of tens of convolutional layers (deep) that train on labelled data (supervised training) to learn target tasks. Labelled training data is composed of thousands of input- output pairs. In the training phase, the networks learn to produce the expected training output (labels) given the training input data. The training is performed by calculating millions of parameter values for feature extraction convolutional filters. In image processing, first layers of trained deep convolutional networks detect simple features, e.g. edges and corners. Based on the low level features extracted in first layers, deeper layers detect higher level features such as contours and shapes.
Using artificial intelligence algorithms, specifically neural networks on microcontrollers offers several possibilities but reveals challenges: limited memory, low computing power and no operating system. In addition, an efficient workflow to port neural networks algorithms to microcontrollers is required. Currently, several frameworks that can be used to port neural networks to microcontrollers are available. We evaluated and compared four of them:
The frameworks differ considerably in terms of workflow, features and performance. Depending on the application, one has to select the best suited framework. On our github page we offer guides and example applications which can help you to get started with those frameworks!
The neural networks that are generated with all those frameworks are static. This means that once they are integrated into the firmware they cant be changed anymore. However, it would be beneficial if the neural network running on the microcontroller could adapt itself to a changing domain. We developed an algorithm (emb-adta) which could be used for unsupervised domain adaptation on microcontrollers. The prototype python implementation is also available on github!
Due to their hardware architecture, Field Programmable Gate Arrays (FPGAs) are optimally suited for the execution of machine learning algorithms. These algorithms require the calculation of millions or even billions of multiplications for each input. To successfully accelerate a neural network, parallel execution of multiplication is the key. The obvious suggestion for parallel execution is a Graphics Processing Unit (GPU), offering hundreds of execution cores. For years, GPU vendors have been adapting the capabilities of their GPUs to meet the demand for narrow integer and floating-point data types used in AI. But still, a GPU will execute one Neural Network (NN) layer after the other, with data transfers between computation cores and memory.
Implementing Neural Networks in FPGAs has several advantages:
Flexible bit widths for both integer and fixed-point data types.
Large numbers of scalable hardware multiplier cores.
Flexibility due to tightly coupled memory blocks with wide parallel interfaces, allowing access to vast numbers of data points in each clock cycle.
Considering the previous points, the FPGA clearly provides all the resources required for highly parallel execution of NN algorithms.
the act of porting a trained network to HDL code for implementation in the FPGA
is not trivial. FPGA vendors have started to provide frameworks for running NNs
in their devices. These include HDL-coded NN-coprocessor cores as IP blocks and
matching compilers to convert a trained NN into a binary executable which will
run on the coprocessor. However, these frameworks are based on a specific
software library and therefore require a processor core running an operating
system and controlling software. This means that the NN input data and network
parameters are transferred from the software to the coprocessor in order to
calculate the output of the NN. The output values are then transferred back to
the software for interpretation.
substantial overhead, especially if the input data is sampled or preprocessed
in the FPGA fabric. It would be preferable to implement the neural network
entirely in the FPGA fabric, capable of running independently from software.
Native Neural Network
Native Neural Network (ZNNN) framework is aimed at the following goals:
Input may be received directly from FPGA fabric
Inference independent of CPU and software
No access to DRAM required
goals in mind, it is obvious that we trade in flexibility to gain performance
and simplicity. The NN is implemented as a rigid block, designed for one single
NN application. To allow for minimum latency, we use dedicated multipliers for
each neuron, and each layer has its own memory block for the weights and
biases. Ping-Pong buffers allow to process one input vector in one layer while
receiving the next input vector. With this structure, pipelining delays can be
minimized to the execution time of the largest layer.
Our framework will take as input a structured text file with a description of the NN, including number of inputs, data-bit widths, fix point precision, number of neurons per layer for fully connected layers, number of filters and kernel size for convolutional layers, max pool and flatting layers. From this configuration file and a training and verification data set, it will generate:
Input A trained NN model
A behavioural model written in C programming language to generate a data set for verification of the VHDL code in simulation
A test bench for verification
The VHDL code of the NN ready for instantiation in your design.
multipliers for the neurons will use a significant amount of the available
resources and it must be noted that larger networks will require considerably
larger devices. This will not be suitable for all NN applications. Our ZNNN
framework is optimally suited for applications such as industrial machine
surveillance where only small networks will meet the latency requirements while
still achieving the required accuracy.
comparison of ZNNN with the Deep Learning Processing Unit (DPU) coprocessor
from Xilinx shows that both have their justification, depending on the
application at hand:
If you need
to run multiple, different neural networks on your FPGA with a fair
performance, you should go with the Xilinx solution. The DPU allows to process
different NN on the same implementation but is restricted to
performance is essential and your application needs a single neural network,
you should use the ZNNN.
of resources in a Xilinx Zynq UltraScale+ EG9 device used by the different
solutions is shown in the following table. The ‘Xilinx DPU’ will always use
roughly the same amount of resources (depending on its configuration). It can
process various neural networks, including very large ones, with a trade-off in
throughput and processing time (latency). The resource requirements of ZNNN
strongly depend on the size and type of NN you implement. ‘ZNNN MNIST’ is a NN
with only dense layers, trained for the well-known MNIST example. MNIST is a NN
application that recognizes handwritten numbers. ‘ZNNN CONV’ is a NN using
1D-convolutional layers for non-linear signal processing in an industrial
application which accepts 64 data points as input. ‘ZNNN VIS’ is a dense
network with 2304 inputs and one single output, used for an industrial
application. According to the large number of inputs, the number of multipliers
required is very large.
Throughput of a NN can be measured in the number of inputs processed per second (FPS). On the Xilinx DPU, the whole NN is processed for one set of input data before the next set can be passed. Our ZNNN framework implements layer pipelining, meaning that as soon as the first layer is processed, the next input set can be accepted as shown in the following figure.
is slightly increased because not all layers have the same processing time, but
all the layers are processed in parallel. In return, the delay between two
inputs is greatly reduced, allowing to process more FPS. Because ZNNN includes
all the required weight parameters in the design, these don’t need to be loaded
into the FPGA at runtime. This allows to increase the FPS by orders of
magnitude in comparison with the Xilinx DPU.
Both the power and the cost of ZNNNs become visible in comparison with the
DPU: The DPU offers the flexibility to run various NNs on one implementation,
including larger NNs like Resnet50. The DPU is controlled by software and
therefore requires a CPU running a Linux operating system. ZNNN implementations
are ideal for small NNs and run independently from software, take their input
directly from FPGA and process orders of magnitude faster than the DPU!
framework is suitable for low latency, high throughput execution of small
convolutional and fully connected NNs. It generates VHDL code for a specific NN
implementation in FGPA without the development overhead of hand-written HDL
code and testbenches. The processing performance of the ZNNN is orders of
magnitude faster than Xilinx’ DPU thanks to a high level of pipelining.
We are aware that the ZNNN implementation can require more FPGA resources than the DPU, but there are industrial applications where this approach is a perfect fit and the achieved performance meets the requirements. With the ZNNN running independently of CPU and software and the input data coming directly from the FPGA fabric, we have principally no bottlenecks in the design.
Our team will continually improve the ZNNN framework by making trade-offs between resource requirements and performance configurable.
A computer with a GPU combined with an FPGA is a powerful tool for high speed video processing. An FPGA can preprocess multiple video streams in realtime and then send the data to the GPU for further processing.
FPD-Link III is a cost-effective solution for high speed video transmission. It has made a name for
itself for its widespread use in the automotive industry. The transmission can be done over a simple
coaxial cable but includes not just a video data stream, but also a bidirectional configuration channel
and a power supply for the camera.
The purpose of this project is to design hardware which makes it possible to take full advantage of the developed FPGA-GPU co design  and to combine it with an FPD-Link III interface. The resulting baseboard utilizes PCI Express implemented in an FPGA which allows connecting up to 6 FPD-Link III. The FPGA is embedded in a system-on-chip and could potentially also be used stand-alone. As a further video source option, it also includes two connectors for MIPI CSI cameras. These are designed to be compatible with RaspberryPi cameras.
In a standard computer, PCI Express (PCIe) offers the possibility for two devices to exchange data on up to 16 high speed data lanes. The CPU is master of the PCIe interface and therefore usually initiates data transfers. This causes overhead and limits the maximum transfer speed for certain applications. The paper FPGA-GPU Codesign from xxx implements solutions to transfer data directly from an FPGA over PCIe to a GPU without the CPU being a bottleneck for the data througput. This approach can be especially useful for applications with high resolution video streams which need to be processed in real time. Live video streams from multiple cameras can be preprocessed in the FPGA and then be transmitted via PCI Express to the GPU for further processing. This thesis is about implementing hardware suitable to take full advantage of this idea.
The goal is to be able to connect multiple cameras to a computer via a PCIe baseboard with an FPGA. The camera interface chosen for this baseboard is FPD-Link III.
FPD-Link III is a cost-effective solution for high speed video transmission. It has gained relevance in
automotive applications. Cameras in cars are becoming more common. Nowadays even low cost cars
come with a rear camera to assist while parking. FPD-Link III can also be used in different industrial
applications, especially for real time use-cases which require high-bandwidth transmissions.
The goal of this project is to develop a Baseboard that makes it possible to connect multiple FPD-Link III cameras to a standard computer with high data rates. The video data from the cameras should be preprocessed in the FPGA and then be forwarded to the computer via PCI Express. Cameras also require to be configured. This configuration will be handled in the FPGA over FPD-Link III.
The Basics of FPD-Link III
Flat panel display link III (FPD-Link III) can be used to receive data from a camera or to send data to a display. The well known standards for high speed video transmission on the consumer market are HDMI, DisplayPort and USB. However, these cables are expensive and better suited for short distances. FPD-Link III can be used with coaxial or a shielded twisted-pair (STP) cables. A 15 m coaxial cable supports data rates up to 6 Gbps and a 10 m long STQ (shielded twisted quad) cable supports up to about 5 Gbps. But FPD-Link III does not only transmit video data. In addition to the video channel, there is also a bidirectional control channel. This is needed for a processor to configure the camera sensor. In case of a display, the control channel can for example be used to send commands from the touchscreen to the processor. The video channel occupies the frequency range between 70MHz and 700MHz whereas the control channel lies between 1MHz and 5MHz. An additional feature of FPD-Link III is Power over coax which offers the possibility to power the image sensor over the coax cable. This eliminates the need for a further cable for power supply.
FPD-Link III to PCIe Video Pipeline
As shown in the figure below, the video is transmitted from a camera sensor to a serializer which sends the video over FPD-Link III in a coaxial cable to the deserializer. The deserializer transmits the data to the FPGA over MIPI CSI-2 D-PHY. In the FPGA, the data can be preprocessed and then be sent over PCIe to the memory on the computer. There will be multiple deserializers on the baseboard so multiple cameras can be connected.
The concept of the Baseboard
The following figure shows a sketch of the concept for the baseboard. The path of the video data is colored in bright green. On the left side there are six coax connectors for the FPD-Link III interface (number of coax connectors is limited to six because of the defined maximum width of a PCIe card). The data goes through the deserializer to the FPGA. From the FPGA the data is transmitted to a computer over PCIe. In addition to the FPD-Link III connectors there are two MIPI CSI-2 D-PHY connectors which are compatable with the RaspberryPi-Camera. This gives the user an additional option for a video source.
The main focus of the project is the deserializer for FPD-Link III, the integration of a SoC FPGA and the PCIe interface. The company Enclustra offers a selection of SoC modules which entail a Xilinx MPSoC (Multiprocessor system-on-chip), SDRAM, flash memory and more. The module can be mounted to the baseboard via connectors. The figure above shows additional hardware and interfaces which are needed for an operating baseboard. The SoC needs a JTAG interface for programming and debugging. An SD-card slot is added and can be used as the boot device. The boot mode switch can be used to change the source device for the boot process. The SoC can be reset over a button and a status LED gives further information about the state of the SoC. The UART (Universal Asynchronous Receiver Transmitter) is needed for the console output of the processor. An ethernet connector makes it possible to get access to the processor with SSH (Secure Shell).
A power switch makes it possible to choose between an external power supply or the 12V supplied
over the PCIe interface from the computer. The external supply is needed when the SoC should be
programmed before the computer is booted. The connection to PCIe devices are established while
booting in the bios, which means the FPGA should be programmed before the computer turns on. The
external supply is also useful when the board consumes more power than the computer can supply.
PCIe can be used in four different lane configurations: 1-, 4-, 8- or 16-lanes. The PCIe switch is used to choose between these options.
FPD-Link III DeSerializer
The deserializer converts the FPD-Link III signal to MIPI CSI-2 which can be connected to the FPGA. Texas Instruments (TI) offers a variety of solutions for FPD-Link III serializers and deserializers. The requirements for choosing a deserializer are the following:
• Input: FPD-Link III LVDS
• Output: MIPI CSI-2
• Able to connect to 2+MP (mega pixel) cameras
TI provides two deserializers which meet the given requirements. These are DS90UB960-Q1 (960) and DS90UB954-Q1 (954). The 960 and 954 models have the same maximum data rates for FPD-Link III and MIPI CSI-2. However, 954 has more GPIO pins per camera. 954 has 7 GPIOs for 2 cameras and 960 has 8 GPIOs for 4 cameras. GPIO signals are useful to get diagnostics of the deserializer, but they can also be used to connect directly to the camera sensor board. Some cameras need for example an enable signal which can be set by the processor over these GPIOs. The deserializer chosen for this baseboard is the DS90UB954-Q1. Below picture shows the available serializers and deserializers from TI
Implementation of the Deserializer
The DS90UB954-Q1 deserializer can be used with one or two camera sensors over FPD-Link III. It supports 2MP@60fps and 4MP@40fps cameras. The two input channels RIN0/RIN1 can be enabled and disabled through registers of the deserializer (Register: RX_PORT_CTL, 0x0C). The input channels can be used as single ended (coaxial channel) or as differential (STP). This baseboard uses single ended coaxial connections. This means the RN- port of a channel is connected to ground with a 15nF-capacitor and a 50 ohm resistor. The RN+ port is connected to the conductor inside the coax connector with a 33nF capacitor in series. This capacitor blocks the receiver ports of the deserializer from any DC voltage. This is especially important if power over coax is used. Power over coax (PoC) makes it possible to use the coaxial cable to supply power to the camera sensor. The output of a power supply is connected to the coaxial connector with a filter in series. This filter is needed to shield the power supply from the AC signal transmitted between deserializer and camera sensor over FPD-Link III.
Typically, the PoC voltage is between 5V and 36V baseboard. Before connecting a camera to the baseboard it must always be checked what PoC voltage is tolerated by the camera board. If needed, the PoC voltage can be cut off from the coax connector design provided from TI.
The FPD-Link III PCIe baseboard was successfully designed and produced. Parts of the baseboard
are tested and verify that the baseboard as such is functional. The components for the MPSoC are
working properly and the baseboard was successfully detected over PCIe. Some tests showed that
there is still work to do in the bring-up of the baseboard.
A task that is still open is the debugging of the PCIe to get a working link with lane width of 8 and 16. The link to a PCIe device is established during the boot of the BIOS (basic input/output system) which is demanding to debug.
Once all these individual parts are completed, they can to be combined into one single system that
collects video streams from multiple cameras and transfers the data to a computer via PCIe.