Control Daemon

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1 Overview

>>>>TODO Overview text.

Currently, booting up the camera is as follows:

  • A systemd service is activated which runs a shell script.
  • This script then loads a bitstream into the FPGA and uses other scripts and C programs to train LVDS channels and set up the HDMI output

When the service is disabled, the user can run this script manually, which:

  • Does not keep the user from running if it has already been activated by systemd.
  • And on the other hand, simple scripts which query the registers (e.g. to get the temperature of the sensor) can be activated even if the FPGA bitstream didn't load.

All of those lead to a solid lockup of the Beta, because if you write to one of those memory addresses which are used for communicating with the PL, and there is no handler in the FPGA, the ARM cores lock up solid, no recovery possible they basically wait for an ACK/NACK forever.

Research is taking place in the Labs here. Code can be found on GitHub

2 Structure

ABTDcd01- AXIOM Control Daemon.png

The control daemon project currently consists of three different modules:

  • Web UI - HTML5, sends requests to the backend, currently by using JQuery (still evaluating alternatives).
  • WSServer - receives WebSocket requests, converts them to Flatbuffers packages and sends them to the daemon, through socket.
  • Daemon - processes flatbuffer packages received over a UNIX domain socket and calls suitable handler.

The communication with the daemon is done via a UNIX domain socket. There are two different protocols used when communicating with the daemon. A handshake protocol which tells the user what parameters and modules are available, their minimum and maximum value, as well as a description.

Preliminary handshake protocol:

    "module": "image_sensor",
    "parameter": "analog_gain",
    "possibleValues": [
      "1/3", "2/3", "1", "3/3", "4/3", "2", "3", "4"
    "currentValue": "",
    "defaultValue": "1",
    "range": [],
    "readOnly": false
    "module": "image_sensor",
    "parameter": "digital_gain",
    "possibleValues": [
      "1", "2", "3", "4", "6", "8", "10", "12", "14", "16"
    "currentValue": "",
    "defaultValue": "1",
    "range": [],
    "readOnly": false

At the moment this parameters are residing in description.json, which is read by the daemon at the initialization phase. If following command is received, then the daemon fills in current values, places the data under value1 and sends it back to caller:

module: general
parameter: available_parameters

The second protocol is used for writing and reading the different parameters. It uses Flatbuffers. The schema for Flatbuffers can be found here.

Communication of the Web UI with the daemon it bridged from the UNIX domain socket and flatbuffers to websocket and JSON by the WSServer. The WSServer accepts following fields, which get translated to the Flatbuffers schema (and vice versa):

Field Type Example Comment
sender string WSServer
module string "image_sensor"
command string "set" or "get"
parameter string "analog_gain"
value1 string "4"
value2 string "5.7"
status string "success" or "fail" used for reply from Daemon
message string status message, to get more info when request fails
timestamp string date and time of camera, when the request was send back to client

TODO: Add JSON/REST package description from Lab (

3 Build

Required packages (names are varying between Linux distributions):

  • cmake
  • clang
  • ninja
  • git


4 Setup daemon

5 Setup WebUI

6 Image Sensor Register Information

Note : Register_num[ x : y ] means we want to access the y+1 th to x+1 th bits of Register_num . So Register 71[15 : 0] means that we want to access the 1st to 16th bit of the register number 71.

Register Overview

Register Name Register Address Default Value Description
Image_flipping 69[1:0] 0

The image coming out of the image sensor, can be flipped in X and/or Y direction. When flipping in Y is enable, the
bottom left pixel (0, 3071) is read out first instead of the top left one (0, 0). When flipping in X is enabled only the
pixels within a channel are flipped on the X-axis, not the channels themselves. Flipping in X is only supported when
using 32 channels per side .

0: No image flipping
1: Image flipping in X
2: Image flipping in Y
3: Image flipping in X and Y

Exp_ext 70[0] 0

The exposure time can be programmed in two ways, externally or internally. Externally, the exposure time is defined
as the time between the rising edge of T_EXP1 and the rising edge of FRAME_REQ .Internally, the exposure time is set by uploading the desired value to the corresponding sequencer register.

0: Exposure time is defined by the value uploaded in the
sequencer register (71-72)
1: Exposure time is defined by the pulses applied to the
T_EXP1 and FRAME_REQ pins

Exp_time 71-72[7:0]

Exp_time[15:0] = Reg 71[15:0]
Exp_time[23:16] = Reg 72[7:0]


When the Exp_ext register is set to ‘0’, the value in this
register defines the exposure time according to the formula

Offset_bot 87[11:0] 780

A digital offset can be applied to the output signal. The value in this register defines the dark level offset
applied to the bottom(OUT1_N/P to OUT32_N/P) output signal (min = 0, max = 4095) More Info

Offset_top 88[11:0] 780

A digital offset can be applied to the output signal. The value in this register defines the dark level offset
applied to the top(OUT33_P/N to OUT64_P/N) output signal (min = 0, max = 4095) More Info

Number_lines_tot 1 3072

The value in this register defines the number of lines read
out by the sensor (min=1, max=3072)

PGA_gain 115[2:0] 0

0: unity gain
1: x2 gain
3: x3 gain
7: x4 gain

PGA_div 115[3] 0

1: divide the output signal by 3

ADC_range 116[7:0] 127

Change the slope and the input range of the ramp used by the ADC More Info

ADC_range_mult 116[9:8] 1

Change the slope and the input range of the ramp used by the ADC More Info

0: 8 bit (x1)
1: 10bit (x2)
3: 12bit (x4)

ADC_range_mult2 100[1:0] 0

Extends the ADC range for slow input clock speeds. `ADC_range_mult`
has to be set to 3 for all bit modes when using this. More Info

0: x4
1: x8
3: x16

7 DaemonCLI

To set/get parameters from command line, DaemonCLI can be used:

Syntax: DaemonCLI <module> set/get <parameter> <value>

7.1 Predefined Commands

Specific commands are available which allow making abstracted parameter changes. The Control Daemon will automatically set all the underlying image sensor register values.


Analog Gain ( Register Info )

DaemonCLI image_sensor set analog_gain 2  // Set the image sensor analog gain to value "2"

This command is equivalent to :

DaemonCLI image_sensor set config_register 115 1  // Setting Gain (x2)
DaemonCLI image_sensor set config_register 116 0x3d5  // ADC_range fine-tuned for gain value
DaemonCLI image_sensor set config_register 100 1  //ADC_range_mult2
DaemonCLI image_sensor set config_register 87 2000 //Bottom channel output offset
DaemonCLI image_sensor set config_register 88 2000 //Top channel output offset

7.2 Setting and Getting Parameters Explicitly

With these commands we can set or get value of each register individually


Number of Lines to be read ( Register Info )

DaemonCLI image_sensor get config_register 1 // get number of lines to be read

Image Flipping ( Register Info )

DaemonCLI image_sensor set config_register 69 2  //Flip image in Y direction

Setting Exposure Time ( Register Info )

DaemonCLI image_sensor set config_register 70 0 // Setting register to use internal exposure mode
DaemonCLI image_sensor set config_register 71 1536 
DaemonCLI image_sensor set config_register 72 0 

Digital Offset Bottom ( Register Info )

DaemonCLI image_sensor set config_register 87 1824

Digital Offset Top ( Register Info )

DaemonCLI image_sensor set config_register 88 1824

7.3 Available modules

general General methods, like getting available parameters through get_available_methods
image_sensor CMV12000 (currently)

7.4 Available parameters (per module)


digital_gain Digital gain
analog_gain Analog gain
config_register read/write arbitrary sensor config register (further parameters are index and value)

8 Development notes

CMV12000Adapter will be used as example. Please look at the class for examples of implementation.

8.1 Add new parameters

Before registering new parameters, two methods should be added: a setter and a getter.

Declaration syntax:

   bool <setter_name>(std::string value1, std::string value2, std::string& message)
bool <getter_name>(std::string& value, std::string& message)

Note the ampersand (&) after the type, it is very important for returning multiple values. As methods can return only one value, bool in this case, variables can be passed by reference (&) to be able to set their values inside methods. Values can be modified as usual and the value will be passed back to the caller (see IDaemonModule.h and MessageHandler.cpp for examples).

Setter receives two values, in case just one is required value2 will be 0 (zero).

After the setter and getter are implemented, it's time to attach them to a parameter name. Here they are registered to gain parameter:

 void CMV12000Adapter::RegisterAvailableMethods()
  AddParameterHandler("analog_gain", GETTER_FUNC(&CMV12000Adapter::GetAnalogGain), SETTER_FUNC(&CMV12000Adapter::SetAnalogGain));
  AddParameterHandler("digital_gain", GETTER_FUNC(&CMV12000Adapter::GetDigitalGain), SETTER_FUNC(&CMV12000Adapter::SetDigitalGain));

This code will attach methods like SetAnalogGain() and GetAnalogGain() to the corresponding parameter "analog_gain".

9 Unit tests

Unit tests have been added to the project to verify correct functionality. Catch2 framework is used because it's single-header only and utilizes the C++11 way of doing things.

Note: (for development on PC) - RAM access of the camera is different from x86/x64 CPUs, modified classes have to be used to bypass this, otherwise SEGFAULT would be the result.

In the CMake scripts a switch called ENABLE_MOCK was added so that users can disable any code which won't work on a regular PC (see CMV12000AdapterTests.cpp for an example). While running the build on camera cmake .. is sufficient, but for development one should use:

$ cmake -DENABLE_MOCK=ON ..