ROS driver for SyncBoard

How to setup

0. Get and build the message/service definition package mars_syncboard_srvs

1. Clone this repo to catkin_ws/src

2. Install the modified version of pigpio.

   cd mars_syncboard/vendors/pigpio
   sudo make install

3. cd to catkin_ws then catkin_make

How to run the node

To manipulate GPIOs of raspberry pi, root privileges are required.

0. roscore
1. sudo su
2. cd to catkin_ws
3. source devel/setup.bash
4. rosrun mars_syncboard syncboard

Or if you prefer to use roslaunch.

1. sudo su
2. cd to catkin_ws
3. source devel/setup.bash
4. roslaunch mars_syncboard example.launch

Then you can play with Syncboard by either calling the services or setting params.

Topics

Topic line/<line_num>

The exact time which Line <line_num> triggered (or is going to trigger) at is published through this topic.

The messages are published once every 1 second, not in real-time.

<line_num> resides in 1,2,8~17.

Topic button

String Message Pressed / Released will be published when the button is pressed / released.

Topic status

All the status info about syncboard. The header.stamp of this topic is set to the exact time of Syncboard.

mars_syncboard_srvs is needed for parsing this topic status on a remote machine. See BoardStatus for defination.

Params

ROS Params can be helpful if you want to monitor the triggering status of each line or to configure multiple lines all at once (e.g. in a launch file). However, it is NOT recommended to configure lines on the fly using rosparam set since it gives you no error message if your new combination of params doesn't make sense.

Syncboard reads the params once per second and will try to configure the lines according to the params. No matter the configuration succeeded or not, Syncboard will then update the params to reflect the actually configuration of the line. Which means (1) if you want to alter more than one param, better set them at once using rosparam load, (2) if the new configuration doesn't make sense, old params will be restored, (3) even if the new configuration does make sense and be applied, the updated params (and the actual triggering setting) may not be identical to your inputs due to rounding.

Param line/<line_num>

There are 5 ROS param for each line:

• line/<line_num>/enabled
• line/<line_num>/trigger_type
• line/<line_num>/freq
• line/<line_num>/offset_us
• line/<line_num>/duty_cycle_percent

<line_num> resides in 1,2,8~17.

The definition is identical to the parameters of service config_line.

The params will not be created (and thus appear in rosparam list) until the line is explicitly configured either by setting the params or using config_line service.

Param gps

There are 3 ROS param for GPRMC:

• gps/baud
• gps/inverted
• gps/offset_us

The definition is identical to the parameters of service config_gps.

Param triggering

The definition is identical to the parameter of service toggle_trigger.

Param led

The definition is identical to the parameter of service toggle_button_led.

Services

Service toggle_trigger

To start or stop triggering on Line 1,2,8~17.

Request and response of toggle_trigger in Message Description Language :

bool start_trigger
---
bool triggering

• bool start_trigger : true to start, false to stop

In normal use cases, lines are configured using config_line before calling toggle_trigger to start and finally stop triggering.

Line PPS and Line GPS is always on.

Service config_line

To configure the signal output on Line 1,2,8~17.

Request and response of config_line in Message Description Language :

uint8 line_num
bool enabled
uint8 trigger_type
float32 freq
uint32 offset_us
uint8 duty_cycle_percent
---
bool succeeded
string msg

• uint8 line_num : The index of the line to be configured.
• bool enabled : If it is true, the line will start triggering after toggle_trigger true
• uint8 trigger_type : 0 for Rising edge, 1 for Falling edge, 2 for Both edge
• float32 freq : Frequency in Hz. Should be in (0,1000]. When the frequency is lesser than 1Hz, SyncBoard will try to trigger the line every $\lfloor 1/freq \rfloor$ seconds.
• uint32 offset_us : Offset/delay of the signal, in microsecond ($10^{-6}$ second)
• uint8 duty_cycle_percent : Duty cycle of the signal, in percentage. If freq is less than 1Hz, the width of the signal is duty_cycle_percent% of 1 second.

Service config_gps

To configure the signal output on Line GPS.

Request and response of config_gps in Message Description Language :

uint32 baud
uint32 offset_us
bool inverted
---
bool succeeded
string msg

• uint32 baud : The baud rate of the GPS time signal. Should be (9600, 14400, 19200, 38400, 56000, 57600, 115200). The default baud rate is 9600.
• uint32 offset_us : Offset/delay of the GPRMC message compared to the PPS rising edge, in microsecond ($10^{-6}$ second). The default offset is 100ms (100*1000 microseconds).
• bool inverted : If it is true, the level of the signal will be inverted. The default setting is false.

Service toggle_button_led

To control the LED on the external button.

Request and response of toggle_button_led in Message Description Language :

uint8 mode
---
uint8 mode

• uint8 mode : 0 for off, 1 for always on, 2 for blinking every 1 second

Utility Node syncboard_button_assist

The syncboard_button_assist node helps ultilize the button on the syncboard, turning on/off the triggering and let the LED to blink/stay-lit when the button is pushed. Rather than manipulating the configuration of the Syncboard hardware directly, it communicates with the syncboard node through ROS topic and params. Simply rosrun mars_syncboard syncboard_button_assist would work, even on a remote machine.