Robobot teensy interface

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Teensy interface

The Teensy_interface app has the functions:

• Translate between the USB connection and the MQTT protocol.
• Adds motor velocity control (allow control using linear velocity and rotation velocity)
• Allow log of almost all relevant data to individual logfiles. Intended for debugging and import into Matlab.
• Monitors the IP addresses of the Raspberry and sends the result to the small Teensy display.

The app is configured with the file robot.ini

Teensy to MQTT

The teensy_interface app can interface with multiple Teensy boards, but for Robobot, only one Teensy board is available.

The Teensy data can be converted to an MQTT message directly, which is the default method.

The Teensy data message for raw line-sensor AD values has the format.:

liv 731 928 962 866 888 902 828 613 50

In MQTT, this will be split into a topic and a message.

topic: robobot/drive/T0/liv 
message: 1736776814.3819 731 928 962 866 888 902 828 613 50

The first part of the topic, robobot/drive/T0, is the same for all messages from the Teensy.

If you want to subscribe to all MQTT messages, the topic request could be robobot/drive/#.

The message is preceded by a timestamp indicating when the message was received from Teensy. The timestamp is seconds from the start of the epoch (1 Jan 1970), which is standard for all PCs

The MQTT block is duplicated. This is unnecessary, as all clients can receive and publish. A timing analysis showed that a receive introduced a 40- to 80-ms delay in publishing. The fix was to establish two clients: one for publication and one for receiving.

Data extract

The most relevant data is decoded in the interface and, in some cases, slightly reformatted before being sent to MQTT.

The decoded data can further be saved to individual logfiles.

Log files

Every time the app is started, typically when rebooted, a new log directory with the timestamp is created. This is the default behaviour.

cd ~/svn/robobot/teensy_interface/build
ls 
CMakeCache.txt           log_20250113_150013.267  Makefile
CMakeFiles               log_20250113_150828.688  out_console.txt
cmake_install.cmake      log_20250113_154849.030  out_err.txt
log_20250113_111703.472  log_20250113_154849.170  robot.ini
log_20250113_135545.064  log_20250113_154849.256  teensy_interface
log_20250113_140824.729  log_20250116_171856.006

Here are the log file directories for 13 Jan and 16 Jan 2025.

Data logging is not started until the Python app is started with the line service.send("robobot/cmd/ti", "log 1"). Logging stops either immediately or after 15 minutes (set in the configuration file). This ensures the disk is not filled with log files when the robot is not on any mission.

The data usage can be relatively high; an example could be:

ls -l log_20250113_150013.267/
total 3288
-rw-r--r-- 1 local local     335 Jan 13 15:00 log_joy_drive.txt
-rw-r--r-- 1 local local    1371 Jan 13 15:00 log_joy_logitech.txt
-rw-r--r-- 1 local local     502 Jan 13 15:00 log_mixer.txt
-rw-r--r-- 1 local local 1447025 Jan 13 15:00 log_mqtt.txt
-rw-r--r-- 1 local local     416 Jan 13 15:07 log_service.txt
-rw-r--r-- 1 local local      76 Jan 13 15:00 log_t0_acc_1.txt
-rw-r--r-- 1 local local   21885 Jan 13 15:00 log_t0_dist.txt
-rw-r--r-- 1 local local  104242 Jan 13 15:00 log_t0_edge_liv.txt
-rw-r--r-- 1 local local   58241 Jan 13 15:00 log_t0_encoder.txt
-rw-r--r-- 1 local local   63071 Jan 13 15:00 log_t0_encoder_velocity.txt
-rw-r--r-- 1 local local      78 Jan 13 15:00 log_t0_gyro_1.txt
-rw-r--r-- 1 local local    3899 Jan 13 15:00 log_t0_hbt.txt
-rw-r--r-- 1 local local  101085 Jan 13 15:00 log_t0_motor_0_pid.txt
-rw-r--r-- 1 local local   99406 Jan 13 15:00 log_t0_motor_1_pid.txt
-rw-r--r-- 1 local local  123413 Jan 13 15:00 log_t0_motor_current.txt
-rw-r--r-- 1 local local  119760 Jan 13 15:00 log_t0_motor_voltage.txt
-rw-r--r-- 1 local local  238992 Jan 13 15:00 log_t0_pose.txt
-rw-r--r-- 1 local local     122 Jan 13 15:00 log_t0_servo.txt
-rw-r--r-- 1 local local  923169 Jan 13 15:00 log_t0_teensy_io.txt
-rw-r--r-- 1 local local    2474 Jan 13 15:00 robot.ini

The first line, total 3288, shows that the log files use 3288 kilobytes of disk space, and this is a 30-second recording. log_t0_teensy_io and log_mqtt hold all communication with the Teensy and MQTT. They are for debugging only and can be disabled in the robot.ini file.

Unused log files can be removed by:

cd ~/svn/robobot/teensy_interface/build
rm -r log_20250113*

In this case, delete all 13 Jan 2025 log files.

Motor control

Motor control translated the drive command, linear velocity (m/s), and rotation speed (rad/s) into a motor voltage sent to the Teensy.

A drive command is typically sent from the Python app by MQTT topic robobot/cmd/ti, e.g. service.send("robobot/cmd/ti", "rc 0.25 0.5") for a linear velocity of 0.25m/s and a rotation speed of 0.5rad/s.

The mixer module calculates each wheel's needed velocity to satisfy the drive command.

The motor module uses closed-loop control to implement wheel velocity. The controller is a PID type. The parameters are configured in the robot.ini file. The measured velocity is taken from the velocity data module.

Gamepad control

There is an optional way to control the robot using a gamepad (Logitech is the only supported brand).

Manual control takes over when the back button on the gamepad is pressed.

Configuration file

All modules are configured by the settings in the robot.ini file. Especially:

• Data subscription from Teensy for essential data (like wheel velocity)
  • data subscription is set by the entries like interval_vel_ms = 15 in the [encoder0] group for 15-ms interval for velocity updates.
• Wheel size and other static configuration data (like wheel radius)
  • Wheel radius is set in the [mixer] group with wheel_radius = 0.077 for 77mm.
• Logfile settings (true or false)

The configuration is divided into groups. All Teensy data groups have an added 0 to indicate the first (and in this case only) Teensy board.

The configuration file is a text file, and a sample (SVN version 1235 (Jan 2026)) is:

[service]
use_robot_hardware = true
logpath = log_%d/
; the '%d' will be replaced with date and timestamp (must end with a '/'). = 
max_logging_minutes = 60.0
log_service = true

[mqtt]
broker = tcp://localhost:1883
context = drive
clientid = tif_data
system = robobot/
function = drive/
print = false
log = true
use = true

[mqttin]
broker = tcp://localhost:1883
context = drive
clientid = tif_cmd
function = cmd/
system = robobot/
log = true
print = false
use = true

[teensy0]
use = true
type = robobot
idx = 105
; robot 'name' and 'idx' are read-only, use command line option to change = 
name = Oliver
device = /dev/ttyACM0
devicealt = /dev/ttyACM1
log = true
print = false
confirm_timeout = 0.04
encrev = true
hardware = 8

[robot0]
log = true
print = false
regbot_version = 1033
batteryusedwh = 106.892433
batterycalibrate = 1.0
robotnamepath = /home/local/svn/log/robotname

[encoder0]
interval_vel_ms = 8
interval_pose_ms = 5
log_enc = true
log_pose = true
print = false
encoder_reversed = false

[imu1teensy0]
interval_gyro_ms = 12
interval_acc_ms = 12
gyro_offset = 0 0 0
log = true
print_gyro = false
print_acc = false

[imu2teensy0]
use = false

[servotn0]
interval_ms = 0
log = true
print = true

[velocity0]
enctickperrev = 68
motorscale = 1 1
useteensyvel = true
log = true
print = false

[motor_teensy_0]
m1kp = 7.0
m1lead = 0 1.0
m1taui = 0.05
m1feedforward = 0
m1maxmotv = 10.0
m1voffset = 0.0
m2kp = 7.0
m2lead = 0 1.0
m2taui = 0.05
m2feedforward = 0
m2maxmotv = 10.0
m2voffset = 0.0
log_voltage = false
m1log_pid = false
m2log_pid = false
m1print = false
m2print = false
interval_motv_ms = 33
interval_motpwm_ms = 0
relax_sec = 3.5

[current_teensy_0]
log = false
print = false
interval_ms = 33

[distforce0]
interval_ird_ms = 25
log_dist = true
log_force = false
print = false
force = false

[edge0]
log = true
print = false
interval_liv_ms = 50
interval_livn_ms = 10

[gpio]
# e.g. pins_out = "20=1 16=0"
pins_out =
stop_on_stop = true
blink_period_ms = 600
log = true
print = false
# GPIO is used by Python script, not here
use = false

[mixer]
use = true
log = true
print = false
driveleft = 0 0 -1
driveright = 0 1 -1
wheelbase = 0.22
motor_gear = 19
drive_gear = 1
wheel_radius = 0.075

[joy_logitech]
log = true
print = false
device = /dev/input/js0

[joy_use]
log = true
print = false
drive_control = true
vel_limit = 0.8
vel_axis = 4
turn_limit = 10.0
turn_axis = 3
button_fast = 5
slow_factor = 0.3
axis_servo = 1
servo = 1
servoscale = 10

[ini]
; set 'saveconfig' to 'false' to avoid autosave = 
saveconfig = true
version = 1215 2026-01-18 11:15:45

Command line options

The teensy_interface has a few command-line options, including help. The command line help is:

cd ~/svn/robobot/teensy_interface/build
./teensy_interface -h
ROBOBOT app
Usage: ./teensy_interface [OPTIONS]
Options:
 -h,--help                   Print this help message and exit
 -v,--version                Compiled SVN version (for uservice.cpp)
 -d,--daemon                 Do not listen to the keyboard (daemon mode)
 -l,--logging-off            Do not start logging right away (wait for MQTT log message)
 -g,--gyro                   Calibrate gyro offset
 -t,--time FLOAT             Open all sensors for some time (seconds)
 -n,--number INT             Set name number to Teensy part [0..150] use with --interface.
 -i,--interface INT          Set interface number to Teensy 0..0 (default is 0)
 -H,--hardware INT           Set robot hardware type (most likely 8) use with --interface.
 -z,--initialization TEXT    Specify which initialisation file to use, default is robot.ini

When the app is started at boot time, the options "-d -l" are used to not start logging and not listen to the keyboard.