TimerInput (Time Between Edges on Digital Ports)
The TimerInput instruction is used to measure the time between edges (state transitions) or frequency on digital ports of the datalogger, including the time between edges or frequency that spans the scan interval.
Syntax
TimerInput ( Dest, StartChan, Edge, Function, Timeout, Timeout_Units )
Example
The following example program measures frequency on the falling edge of C1.
'Declare Variables
Public TimeIn(2)
Public scan_cnt
'TimerInput(dest,startchan,edge,function,timeout,units)
'function 1 -> period
'2 -> frequency
'3 -> time since previous
BeginProg
Scan(1000,msec,10,0)
scan_cnt = scan_cnt + 1
TimerInput(TimeIn(1),C1,0,2,0,usec)
NextScan
EndProg
Remarks
This instruction measures the timing of the edges on the control ports. The instruction can be used in Low Frequency Mode (<1 kHz) for edge timing, period, and frequency measurements or in High Frequency Mode (up to about
Parameters
Dest
The Dest parameter is a variable array in which to store the results of the measurement. The array must be dimensioned equal to the number of ports for which results are requested.
Type: Variable or Array
StartChan
The channel to use as a reference for edge timing for this instruction.
| Code | Description |
|---|---|
| C1 | Control Port 1 and 2 |
Type: Constant
Edge
The Edge parameter is a digit (0 or 1) that represents each of the ports, from left to right: C8….C1. If a 1 is entered for a port, the transition will be counted on the rising edge (from <1.5V to >3.5V). If a 0 is entered, the transition will be counted on the falling edge (from >3.5V to <1.5V). For example, getting a rising edge on C8 starting at C1 would be done with: TimerInput(Dest,C1,10000000,20000000,0,usec).
| Digit | Edge |
|---|---|
| 0 | falling |
| 1 | rising |
Type: Constant
Function
The Function parameter is a value where each digit represents the function for the channel associated with that digit (see Edges, above). Leading 0s do not have to be used if you are using only the first few channels for the instruction. For example, measure the frequency on the falling edge of C1 could be specified with either: TimerInput(Dest,C1,0,2,0,usec) or TimerInput(Dest,C1,0000,0002,0,usec).
| Function | Result |
|---|---|
| 0 | The associated channel is not used. |
| 1 | Calculate the period of the signal on the specified channel (in microseconds). |
| 2 | Calculate the frequency (Hz) for the specified channel. |
| 3 | Calculate the time from an edge on the previous channel (1 number lower) to an edge on the specified channel (in microseconds) |
| 5 | Return the count of edges since the last execution. |
Type: Constant
Timeout
Used to determine the results to be returned when no changes have occurred in the specified ports since the last execution of the instruction. If the timeout period has expired and no change has occurred, a null value will be returned (0 for frequency and NaN for period or time since last edge). If the timeout period has not expired the last valid result will be returned. This is useful for measuring signals with periods greater than the scan interval. The maximum Timout is 2^32 x the scan. Typically, a timeout value is at least one scan interval. However, 0 can be entered to make the calculation each time the instruction is executed. A timeout less than the scan interval will default to the scan interval.
Type: Constant (or expression that evaluates as a constant) or Variable
Timeout_Units
The units for the Timeout parameter. Right-click the parameter to display a drop-down list box.
| Code | Description |
|---|---|
| μsec | microseconds |
| msec | milliseconds |
| Sec | seconds |
| Min | minutes |
Type: Constant