Data Processor URI Scheme

An alternative to configuring data processors (filters and transformers) is to use a String URI. The configuration URI is a combination of a scheme and query string. The scheme and query string are separated by a question mark (?) and the query fields are separated by an ampersand (&).

"[scheme]?[field1=value1]&[field2=value2]...&[fieldN=valueN]"

The following tables provide a brief overview of the available transformers and filters and their scheme string. Further details about each scheme is given in the below sections.

Transformer	Description	Scheme
Accumulator	Computes a running sum of all data received	accumulator
Average	Calculates a running average of the input data over a given sample size	average
Math	Performs a mathematical operation on the input	math
Rms	Combines multi-component data by computing root mean square	rms
Rss	Combines multi-component data by computing root sum square	rss
Time	Periodically output the difference between the current and previous input	time

Filter	Description	Scheme
Comparison	Only allow data through that satisfies the comparison	comparison
Passthrough	A gate that users can manually control	passthrough
Time	Periodically allow data through	time

Accumulator

Field	Description	Required
output	Output size of the running sum. If not specified, it will infer the output size based on the input	No

///< equivalent to: transform(new Accumulator((byte) 4))
///< accumulate input and allocate 4 bytes for the output regardless of input
transform("accumulator?output=4")

///< equivalent to: fromSwitch().transform(new Accumulator())
///< accumulate input and infer the output size based in the input signal
///< will implicitly allocate 1 byte because switch data is only 1 byte
fromSwitch().transform("accumulator")

Average

Field	Description	Required
sampleSize	How many data samples to compute a running average of	Yes

///< equivalent to: transform(new Average((byte) 16))
///< Compute a running average over the past 16 samples
transform("average?sampleSize=16")

Comparison

Field	Description	Required
operation	Sets the comparison used to filter data	Yes
reference	Value on the right hand side of the operation the input data is compared to	Yes
signed	Force a signed or unsigned comparison. If not specified, this field will be inferred from the input signal	No

Operation	Description	Value
Equals	True if input and reference are equivalent	eq
Not equals	Opposite result of equals to comparison	neq
Less than	True if input is less than the reference	lt
Less than or Equals	True if input is less than or equal to the reference	lte
Greater Than	True if input is greater than the reference	gt
Greater Than Or Equals	True if input is greater than or equal to the reference	gte

///< equivalent to: filter(new Comparison(Comparison.Operation.EQ, 511))
///< Only allow data that is equal to 511 to pass, infer signed or unsigned based on input
filter("comparison?operation=eq&reference=511")

///< equivalent to: filter(new Comparison(Comparison.Operation.LTE, 511, true))
///< Only allow data less than or equal to 511 to pass, use a signed comparison
filter("comparison?operation=lte&reference=511&signed=true")

Math

Field	Description	Required
operation	Sets the mathematical operation to perform on the data	Yes
rhs	Value on the right hand side of the operation	Depends, yes if operation requires 2 inputs, no otherwise
signed	Force a signed or unsigned operation, If not specified, this field will be inferred from the input signal	No

Operation	Description	Value	# Operands
Addition	Adds the input data with an offset	add	2
Multiplication	Multiplies the input data by a scale factor	mult	2
Division	Divides the input data by a scale factor	div	2
Modulus	Computes the remainder of the input data and a divisor	mod	2
Exponent	Computes exponentiation using the input as the base, and the rhs value as the exponent	exp	2
Square Root	Computes square root of the data	sqrt	1
Left Shift	Performs a left shift of the data	lshift	2
Right Shift	Performs a right shift of the data	rshift	2
Subtraction	Subtracts the input data with an offset	sub	2
Absolute Value	Computes the absolute value of the ipnut	abs	1

///< equivalent to: transform(new Math(Math.Operation.ADD, 273.15))
///< Add 273.15 to the input, infer signed operation based on input
transform("math?operation=add&rhs=273.15")

///< equivalent to: transform(new Math(Math.Operation.ADD, 273.15, true))
///< Add 273.15 to the input with signed addition
transform("math?operation=add&rhs=273.15&signed=true")

Passthrough

Field	Description	Required
mode	Sets the operation mode	Yes
value	Sets the value or condition corresponding to the passthrough mode	Depends, yes for conditional and count modes, no otherwise

Mode	Description	Value
All	Allow all data to pass through	all
Conditional	If value is 0, unconditionally block all data. If value is 1, allow all data through	conditional
Count	Only allow a fixed number of data samples through	count

///< equivalent to: filter(new Passthrough())
///< passthrough filter allowing all data through
filter("passthrough?mode=all")

///< equivalent to: filter(new Passthrough(Passthrough.Mode.CONDITIONAL, (short) 0))
///< do not allow data through for now
filter("passthrough?mode=conditional&value=0")

///< equivalent to: filter(new Passthrough(Passthrough.Mode.COUNT, (short) 4))
///< only allow 4 samples through
filter("passthrough?mode=count&value=4")

Rms

No query string required for rms.

///< equivalent to: transform(new Rms())
///< Compute RMS value of the accelerometer XYZ axis data
fromAccelAxis().transform("rms")

Rss

No query string required for rss.

///< equivalent to: transform(new Rss())
///< Compute RSS value of the accelerometer XYZ axis data i.e. vector magnitude
fromAccelAxis().transform("rms")

Time

Field	Description	Required
period	How often to allow data through. Specify value in milliseconds	Yes

///< equivalent to: transform(new Time(10000))
///< Allow the difference between the current and previous value through every 10 seconds
transform("time?period=10000")

///< equivalent to: filter(new Time(15000))
///< Allow data through every 15 seconds
filter("time?period=15000")