sangbay_driver

ROS Noetic driver for Sangbay gas sensors — S-M4, S-M4T and K-5S Modbus modules (any gas, several per RS485 bus) and the GT-TS01A / SLTD-CH4-100 laser methane sensors, all from one config file.

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List your sensors in a YAML file and every one gets its own topics. Sensors on the same serial port share it (one thread per port), a sensor that stops answering only affects itself, and unplugged adapters are reopened. The protocol code has no ROS dependency and is also usable from sangbay_tool. Only standard messages are used.

Docs: supported sensors and protocols · first run · datasheets

type	Products	Link	Unit
module	S-M4, S-M4T (TTL), S-M4T 485, K-5S, with any head (S4-H2S-100, MJC4-2.8J, N-CH4, ...)	Modbus RTU 9600, address 0..254	from the module (ppm, %LEL, %VOL, ...)
gt_ts01a	GT-TS01A laser methane	ASCII 115200, every 2 s	%VOL
sltd_ch4	SLTD-CH4-100 laser methane remote sensor (100 m)	binary 115200, every 50 ms	ppm·m

Quick start

mkdir -p ~/catkin_ws/src && cd ~/catkin_ws/src
git clone https://github.com/DarmawanRobotics/sangbay_driver.git
cd ~/catkin_ws
rosdep update --rosdistro noetic --include-eol-distros
rosdep install --from-paths src --ignore-src -y --rosdistro noetic
catkin_make && source devel/setup.bash
sudo usermod -aG dialout $USER                       # serial access, then log in again

# one module at the factory address
roslaunch sangbay_driver sangbay.launch port:=/dev/ttyUSB0
# your own list
roslaunch sangbay_driver sangbay.launch config:=/path/to/sensors.yaml

Several sensors

rate: 1.0
sensors:
  - {name: h2s, port: /dev/ttyUSB0, address: 1, expected_gas: H2S, alarm_threshold: 10}
  - {name: co,  port: /dev/ttyUSB0, address: 2, expected_gas: CO}
  - {name: o2,  port: /dev/ttyUSB0, address: 3, expected_gas: O2}
  - {name: ch4_laser,  type: gt_ts01a, port: /dev/ttyUSB1}
  - {name: ch4_remote, type: sltd_ch4, port: /dev/ttyUSB2, mode: dynamic, pointer: true}

Every module leaves the factory on address 255. To put several on one RS485 bus, connect them one at a time and give each its own address:

rosrun sangbay_driver sangbay_tool set-address --port /dev/ttyUSB0 --address 255 --new 1
rosrun sangbay_driver sangbay_tool scan --port /dev/ttyUSB0      # afterwards, all on the bus

All keys are explained in example_multi.yaml. Use /dev/serial/by-id/usb-... as port so the names stay the same between boots.

Interface

Per sensor, under /sangbay/<name>/:

Topic	Type
concentration	std_msgs/Float32	in unit; not published while the module preheats
unit	std_msgs/String	ppm, %LEL, %VOL, ppm*m, ... (latched)
status	std_msgs/String	NORMAL, PREHEATING (12.3 s), HIGH, STEL, SENSOR-ERROR, NO DATA: ... (latched)
alarm	std_msgs/Bool	gas alarm: the module's alarm bits, over range, or alarm_threshold (latched)
fault	std_msgs/Bool	sensor damaged, laser abnormal, or no data (latched)
temperature, pressure	std_msgs/Float32	GT-TS01A: compensation temperature °C, kPa
light_intensity, laser_temperature	std_msgs/Float32	SLTD-CH4-100: return signal, raw laser temperature

/diagnostics has one entry per sensor (sangbay: <name>, hardware id port#address) with every detail: gas, raw value, decimals, status word, each flag. OK, WARN on alarm or preheating, ERROR on fault or no data.

Usage

rostopic echo /sangbay/h2s/concentration
rostopic echo /sangbay/h2s/status
rosrun rqt_runtime_monitor rqt_runtime_monitor

# without ROS
rosrun sangbay_driver sangbay_tool scan --port /dev/ttyUSB0
rosrun sangbay_driver sangbay_tool read --port /dev/ttyUSB0 --address 1 -v   # -v: Modbus frames
rosrun sangbay_driver sangbay_tool read --type gt_ts01a --port /dev/ttyUSB1
rosrun sangbay_driver sangbay_tool read --type sltd_ch4 --port /dev/ttyUSB2

import rospy
from std_msgs.msg import Bool, Float32

rospy.init_node('gas_monitor')
for name in ('h2s', 'co'):
    rospy.Subscriber('/sangbay/%s/concentration' % name, Float32,
                     lambda m, n=name: rospy.loginfo('%s %.2f', n, m.data))
    rospy.Subscriber('/sangbay/%s/alarm' % name, Bool,
                     lambda m, n=name: m.data and rospy.logwarn('%s alarm', n))
rospy.spin()

Troubleshooting

Symptom	Fix
cannot open /dev/ttyUSB0: ... Permission denied	dialout group (above)
address 1: no answer	A/B swapped, no power, wrong address: sangbay_tool scan
several modules answer garbage	two modules on the same address: set them one at a time
CRC error / short answer	noise: shorter cable, 120 Ω termination at both ends, lower rate
module reports CO, expected H2S	a different head or module on that address
GT-TS01A / SLTD no data	115200 baud, TX/RX crossed, 5 V supply; see first_run.md

Develop

catkin_make run_tests && catkin_test_results build/test_results
rosrun sangbay_driver fake_devices.py --bus /tmp/sangbay_bus --gt /tmp/sangbay_gt --sltd /tmp/sangbay_sltd &
roslaunch sangbay_driver sangbay.launch config:=$(rospack find sangbay_driver)/config/example_fake.yaml

The unit tests check the frames against the datasheet examples and run the buses against simulated modules (several on one line), a GT-TS01A and an SLTD-CH4-100 on pseudo terminals, including dropouts and reconnects; the rostest runs the launch file against them. CI runs both on ros:noetic.

Released under the Apache License 2.0.