Wifi fast.py
- BiomechDocs BL Knee PFresearchE
- Biomech Documentation links:
- AKCPU2z BLMD6c BLFT6c PSER1c Imu_2010 Emg_2009 Ric Upd_pcb
wifi_fast.py is the primary utility for receiving real-time telemetry from the target. It makes connection to the target via either a standard RS-232 serial port, or via a TCP connection. Once connected it reads telemetry, can log the data to a file, and can send the data via UDP for real-time plotting. It also sends keyboard characters to the target which can then be read via the C function 'getchar'.
basic command line options
- get help with wifi_fast.py -h
The typical command contains 3 or 4 options as show below. wifi_fast.py -f log_file_name -V dataport3d -F -i IP_ADDRESS
- -V option specifies a "Vlist" or variable list that describes the binary format of the telemetry packet. These vlist files live in "support_scripts\vlist". Some times matching the vlist to the firmware can be a challenge - as the two need to be precisely the same length; and the variable types must also match.
- -f option specifies the base name of the log file.
- As data is received, it converted as specified by the #vlist, and stored in a self documenting .txt file that has a time stamp suffix. Several times an hour a new file will be started and the previous one added to a zip file.
- The zip file often contains a file called "wifiload.m" that can be used with matlab to read the file and create a data structure with named fields. However, there are now easier to use matlab functions for this purpose.
- The "-f xx" file option is a special case that means no-logging.
- -F : this command line option causes wifi_fast to send a command to the SWIFI for it to flush its FIFO. When there is not connection, this FIFO will fill w/data and may take ~1min to be depleted when full.
- -i, -p : one of these options is required as it specifies how to connect to the target. The -i option specifies an IP address (or resolvable machine name), while the -p option specifies a serial port.
making a connection to the robot
via a wired connection
A wired ASYNC serial connection with the target requires a minimum of 3 wires : GND, Tx, Rx. The signals are 3.3V logical level. Several USB serial port devices called "PSER" have been made for this purpose. When connected to the PC, they will be assigned a "COMM PORT" number. Under windows you can use the "Device manager" to list the serial ports. You can run the command directly with the command "devmgmt"
via a wireless connection
The robot uses a "SWIFI" to make a connection to a 2.4Ghz "G" access point. The SWIFI needs to be pre-programmed to know what access point to connect to.
- In lab the access point is : bmech4.media.mit.edu
- You can also test connectivity with ping bmech4.media.mit.edu
From the support scripts folder run :
matlab support
A number of helpful matlab scripts and functions live in "support_scripts" and "support_scripts\matlab_support". It is help to add these directories to your matlab path. Setting the path can be done from the "File -> Set Path" dialog from the main matlab window.
plot_float : real_time plotting
The command "plot_float.m" is used to listen to a UDP port, and plot the data received on that port. When started, plot_float prompts for a port number (typically 9999) to listen on. Afterward, it runs the script "user_ui.m" and reads the file "auto_ui_9999.txt" for configuration.
user_ui.m
This file contains settings that should be user or machine specific.
- The PLOT_ORDER list specifies what data fields to be plot, and in what order.
- PLOT_NUM_X and PLOT_NUM_Y specify the initial number of subplots to use.
- A full example:
PLOT_ORDER = 1:8
PLOT_NUM_X = 4;
PLOT_NUM_Y = 2;
if ~exist('matlab_listen_port')
matlab_listen_port = 9999;
else
disp( sprintf('Listen port %d', matlab_listen_port));
end
SAMPLE_RATE = 500; % sample rate of system feeding the python bridge
PLOT_UPDATE_INTERVAL = 1.0; % time interval between updates of the plot window
DATA_WINDOW_TIME = 10.0;
PLOT_WINDOW_TIME = 10.0;
PLOT_SUBSAMPLE = 1;
data_type = 'float';
SAMPLES_PER_UDP_PACKET = 10;
auto_ui_9999.txt
The auto_ui_nnnn.txt file is AUTO generated by wifi_fast.py. The nnnn is substituted with the UDP port number. It contains a matlab parse-able version of the .vlist file.
reading SWIFI data files with matlab
- wifiload.m
- data = wild(file_name_pattern)
- obj = wild_cvt_dirlist(directory_pattern)
off line plotting data and objects
- pit.m
- gpit.m
- spit.m
vlist
A vlist file (located in support_scripts/vlist) contains a list of: data types, variable names, scaling factors, and offsets
When wifi_fast is started, the vlist file specified by "-V" is read and use to decode the data packet coming from the "SWIFI". wifi_fast also creates a file "auto_ui_9999.txt" - this file is a simplified format of the vlist that is read by the matlab plotting program "plot_float.m"
The standard vlist is :
# type name scale (1 by def) offset (0 by def) int8 sc_state_trans int8 state int16 raw_hall_sensor int16 qIq 1./866. int16 motor_speed int16 ibat 1.0/866. 0 uint16 vbat 30.0/65536 0 int16 motor_state int16 qV 1.0/1093 int32 MC_encoder #SC variables (from here down) float ts_confidence float pff_torque float estimated_torque # Raw IMU Data int16 gyro_idg_x_nAx 2.0 int16 gyro_idg_y_nAz 2.0 int16 gyro_adi_z_pAy 2.0 int16 acc_mot_x_nAz 2.0 int16 acc_mot_y_pAx 2.0 int16 acc_mot_z_nAy 2.0 # IMU Data int16 imuFlags int16 imuTerrainAngle 1.0/100.0 int16 imuZacceleration 1.0/100.0 int16 imuPitch 1.0/100.0 int16 imuWalkVelocity 1.0/100.0 int16 imuVelocityAngle 1.0/100.0 int16 imuPitchVelocity 1.0/100.0 int16 imuAccAngle 1.0/100.0
firmware dataport generation
- in the SC file "dataport.c" there is the statement : switch(sc_dp.dataport_select)
- for each case, there are a number of assignment of robot variables to variables of the form "pf[n]".
- the special command "157" is used to set the value of the variable "sc_dp.dataport_select"
- thus the command "do_command.py -i IP_ADDRESS -s 157 1" sets dataport select to 1.
