Log file format description.
Log file format version: 4
Base format: JSON
HEADER Describes the configuration of the test hardware. Fields: version : Log file format version number (int, 4) firmware : Firmware name and version number (str) rate_ms : Interval between records in milliseconds (int) date : Date at which recording began (YYYY/MM/DD) time : Time at which recording began (HH:MM:SS 24hr) sensors : Array of sensor descriptors servos : Servo configuration pid : PID controller configuration
SENSOR Descriptor:
name : Name of sensor (str, 3 chars)
num : Number of sensors of this type (optional, int)
rate : Sample rate for this sensor (optional - if not provided, assumed 1 per record, int)
rate_units : Sample rate units, typically milliseconds (ms), but could also be per rotation (pr) etc. (optional - must be provided if rate is specified, str)
units : Units measured, eg m.Nm (str)
min : Minimum sensor value (optional)
max : Maximum sensor value (optional)
scale : Power of 2 scale factor
SERVOS Configuration :
num : Number of servos (int)
rate : Servo position update rate (int)
rate_units : Servo update rate units, typically milliseconds (str) (Not sure why this would be anything other than ms)
units : Servo position units, typically LSB (str)
min : Minimum position value
max : Maximum position value
names : Array of servo channel names, eg "throttle" (str) (length must match 'num')
PID Configuration :
rate : PID update rate (int)
rate_units : PID update rate units, typically milliseconds (str) (Not sure why this would be anything other than ms)
k_frac : Number of fractional bits used for coefficients (int)
configs : Array of configurations for each PID controller:
name : Name of PID controller (str)
src : Name of sensor input (str)
idx : Index of sensor where there are multiple sensors with the same name (idx)
dst : Name of servo output (str)
kp : Proportional coefficient (fixed point int)
ki : Integral coefficient (fixed point int)
kd : Derivitive coefficient (fixed point int)
RECORDS Records data at fixed intervals. Array of RECORD : timestamp : Timestamp of record in milliseconds (int) (name of sensor) : 2D Array or sensor index/sensor values for sensor , not including sensors without a 'rate' property _t0 (name of sensor) : Time offset of first sample for sensor with non fixed update rates, typically 'spd' which records tacho pulse intervals (int) avg: Dictionary of average values for each sensor (including those without a 'rate'), servo and the coefficients of each PID pid: Array of PID parameter reports: trg : Target value act : Input value err : Difference between trg and act out : Output value (sum of p i and d) p : proportional component (kp * err) i : integral component (need to check if this is pre or post scaled) d : derivative component (kd * (err-err_old)?)