Configuring Counters in LJControlPanel

1. Open the device in LJControlPanel.
   
   Follow steps 1-6 in our U3/U6/UE9 Quickstart Tutorials.
    
2. Click the "Config" button in the Timer/Counter section of the Test panel.
   
   Once pressed, a new window should appear with more timer and counter settings.
   
   
    
3. Enable your counters.
   
   For this tutorial we will enable one counter on FIO4.
   
   Ensure "# Timers Enabled" is 0 and click the "Enable" box for Counter 0.
   
   
    
4. Set the "Pin Offset".
   
   Set the "Pin Offset" entry to 4 to put Counter0 on FIO4. This is most convenient for U3 users; U6 or UE9 users could apply a pin offset of 0 to put Counter0 on FIO0. Note that the minimum pin offset for the U3 is 4. See the timer/counter datasheet page of the U3 for more information.
   
   If any timers were enabled they would appear on the DIO before the counters. For example, if two timers and Counter0 are enabled with a pin offset of 4, the timers would appear on FIO4 and FIO5 and Counter0 would appear on FIO6.
   
   
    
5. Click "OK".
   
   The smaller timer/counter window will close and you should now see your counter value incrementing if you have a good pulse input attached to the counter0 DIO pin. If you are unsure if you have a good pulse input, a jumper wire clamped in a GND terminal should produce increments when you tap the other end of the wire to the inside-back of the timer/counter DIO pin terminal_[1]. Clicking inside the Counter0 reset box will reset the counter back to 0. 
   
   
    
6. Troubleshooting an input.
   
   With a typical counter signal, you would connect signal+ to the counter DIO (FIO4 in this tutorial) and connect signal- to a GND terminal on the LabJack.
   
   The necessary connections for your signal could depend on the details of your signal. Some further resources that may be useful for troubleshooting a digital signal are the Driven Signals and Open-Collector Signals app notes.
   
   Always ensure you have a good electrical connection from your signal to the LabJack. Touching a conductor to the top of the screw head of an un-clamped screw terminal is rarely a valid electrical connection. The screw head is usually a valid connection point when the terminal is clamped, but the only guaranteed valid connection is to securely clamp a conductor/ signal wire inside the screw terminal.
   
   If your signal is not giving you counts, use a DMM or oscilloscope to confirm you have valid voltages on the DIO line. The counter/digital input in this example is looking for a rising edge, which means that the state of the digital input changes from low to high. On UD devices a low is less than 0.8V and a high is greater than 2.00V. See the specifications in your device datasheet for further details U3/U6/UE9.
   
   If too many edges are being detected: If the signal is very noisy it can cause multiple fast edges rather than a single edge. A simple low pass RC filter (e.g. R=1k and C=0.01uF gives a cutoff frequency of 16kHz) is a possible solution, but the problem suggests the signal is very noisy and could be a symptom of improper connection. Mechanical switch signals can be susceptible to switch bounce, which can result in additional edges; see our Switch Signal app note.
    
7. [Optional] Save your timers and counters in your startup configuration.
   
   This is suggested if using LJLogUD, LJStreamUD, or other simple polling programs, but not needed if your software will do the configuration. Also note that U3 hardware revisions 1.20 and 1.21 do not support timer/counter startup configurations.The U3-LV and U3-HV are hardware revision 1.30.
   
   To save your timers and counters for startup you must set up the timers/counters in the Config  Defaults panel of LJControlPanel rather than the Test panel.
   
   First, close the Test panel and click "Config Defaults".
   
   
   Set up all of your timer/counter settings.
   
   
   Click "Write Values". A new window will pop up; Click "Yes" to save your configuration.
   
   
   Close LJCP and power cycle the device to apply your changes. Note that the Test panel will not load your configurations, so we recommend you test the feature in LJLogUD.  You can also return to the Config Defaults panel in LJCP to see if it shows the power up defaults you set.

[1] LabJack digital inputs have an internal 100k pull-up that weakly holds them high, so when you connect a GND wire to a digital input it will pull the line low and create a falling edge. When you pull out the wire you get a rising edge.  You are not likely to make a perfectly clean single contact, so a counter will typically increment many counts each time you tap the wire.  Also note that you should touch the ground wire to the inside-back of the counter terminal.

Next Step:

The following forum topic describes how to do frequency measurement with a counter. You can also move on to Configuring a Timer or subsequently Logging Timers/Counters.

Configuring Timers in LJControlPanel

1. Configure a counter.
   
   If you are using an input timer feature (period measurement, etc.) we recommend you first configure a counter and get it to increment properly before attempting to configure a timer.
    
2. Open the device in LJControlPanel.
   
   Follow steps 1-6 in our U3/U6/UE9 Quickstart Tutorials.
    
3. Click the "Config" button in the Timer/Counter section of the Test panel.
   
   Once pressed a new window should appear with more timer and counter settings.
   
   
    
4. Enable your timers.
   
   For this tutorial we will set up a firmware counter on Timer0, but note that there are several other timer options available. See the timer/counter datasheet page of your respective device for more information: U3/U6/UE9.
   
   Set "# of Timers Enabled" to 1 and change the mode of Timer0 to FIRMCOUNTER.
   
   
    
5. Set the "Pin Offset".
   
   set the "Pin Offset" entry to 4 to put Timer0 on FIO4. This is most convenient for U3 users; U6 or UE9 users could apply a pin offset of 0 to put Timer0 on FIO0. Note that the minimum pin offset for the U3 is 4. See the timer datasheet page linked in step 3 for more information.
   
   
    
6. [Optional] Change the timer clock frequency and divisor.
   
   Selecting a clock base with a divisor will automatically pop up a window for modifying the TimerClockDivisor as shown below.
   
   
    
7. Click "OK".
   
   The smaller timer/counter window should close and you should now see your timer value incrementing if you have a good pulse input attached to the timer DIO pin. If you are unsure if you have a good pulse input, a jumper wire clamped in a GND terminal should produce increments when you tap the other end of the wire to the inside-back of the timer/counter DIO pin terminal_[1].
   
   
    
8. Troubleshooting an input signal.
   
   With a typical digital signal source, you would connect signal+ to a capture timer DIO (FIO4 in this tutorial) and connect signal- to a GND terminal on the LabJack.
   
   The necessary connections for your signal could depend on the details of your signal. Some further resources that may be useful for troubleshooting a digital signal are the Driven Signals and Open-Collector Signals app notes.
   
   Always ensure you have a good electrical connection from your signal to the LabJack. Touching a conductor to the top of the screw head of an un-clamped screw terminal is rarely a valid electrical connection. The screw head is usually a valid connection point when the terminal is clamped, but the only guaranteed valid connection is to securely clamp a conductor/ signal wire inside the screw terminal.
   
   If your signal is not giving you good measurements, use a DMM or oscilloscope to confirm you have valid voltages on the DIO line. The digital input set up in this tutorial is looking for a rising edge, which means that the state of the digital input changes from low to high. On UD devices a low is less than 0.8V and a high is greater than 2.00V. See the specifications in your device datasheet for further details U3/U6/UE9.
    
9. [Optional] Advanced testing.
   
   For more advanced testing of other features such as frequency input and PWM output, multiple timers and counters could be configured. See our Advanced Timer/Counter Testing tutorial.
    
10. [Optional] Save your timers and counters in your startup configuration.
    
    This is suggested if using LJLogUD, LJStreamUD, or other simple polling programs, but not needed if your software will do the configuration. Also note that U3 hardware revisions 1.20 and 1.21 do not support timer/counter startup configurations.The U3-LV and U3-HV are hardware revision 1.30.
    
    
    To save your timers and counters for startup you must set up the timers/counters in the Config Defaults panel of LJControlPanel rather than the Test panel.
    
    First close the Test panel and click "Config Defaults".
    
    
    Set up all of your timer/counter settings.
    
    
    Click "Write Values". A new window will pop up; Click "Yes" to save your configuration.
    
    
    Close LJCP and power cycle the device to apply your changes. Note that the Test panel will not load your configurations, so we recommend you test the feature in LJLogUD.  You can also return to the Config Defaults screen in LJCP to see if it shows the power up defaults you set.

[1] LabJack digital inputs have an internal 100k pull-up that weakly holds them high, so when you connect a GND wire to a digital input it will pull the line low and create a falling edge. When you pull out the wire you get a rising edge.  You are not likely to make a perfectly clean single contact, so a counter will typically increment many counts each time you tap the wire.  Also note that you should touch the ground wire to the inside-back of the counter terminal.

Next Step:

Once you are all set up with your timers and counters you can move on to Logging Timers/Counters.

Testing PWM and Input Capture Timer Features Using LJControlPanel

1. Get familiar with basic timer and counter setup in LJControlPanel.
   
   See our tutorial for configuring counters in LJControlPanel.  Then, see our tutorial for configuring timers in LJControlPanel.
    
2. Open your device in LJControlPanel, open the Test panel, then navigate to the timer/counter configuration window.
   
   
    
3. Enable two timers and Counter0.
   
   Set the Timer0 "Mode" selection to PWM16 and Timer1 "Mode" selection to RISINGEDGES32.
   
   Leave the "TimerClockBase" as the default 48MHz clock. This will result in a PWM frequency of ~732Hz. The Timer0 "Value" entry determines the PWM low time and therefore the duty cycle when using the PWM16 feature. The default value of 32768 will produce a 50% duty cycle. See the PWM16 feature documentation for more information.
   
   Click the "Enable" box for Counter0 and set the "Pin Offset" entry to 4. This configuration will result in a PWM output (Timer0) on FIO4, Period measurement (Timer1) on FIO5, and Counter0 on FIO6. This configuration is most convenient for U3 users; U6 or UE9 users could apply a pin offset of 0 to put Timer0 on FIO0, Timer1 on FIO1, and Counter0 on FIO2. The following steps assume a pin offset of 4 is used.
   
   
    
4. Connect a wire between the Timer0 and Counter0 DIO.
   
   Select "OK" in the timer/counter configuration window to apply your changes. When you connect Timer0 (FIO4) to Counter0 (FIO6) you should see the "Value" section of Counter0 increasing if the PWM is set up correctly. LJControlPanel updates values approximately 1 time per second, so a PWM set up with a frequency of 732Hz should result in the Counter0 value incrementing approximately 732 counts each update. 
   
   If you do not see the proper count increment, ensure your wire is firmly screwed down into the Timer0 and Counter0 terminals and otherwise check your timer/counter configurations for errors.
   
   
    
5. Move or add a wire to connect the Timer0 and Timer1 DIO.
   
   The previous step should verify the operation of the PWM output feature. A wire could then be connected between Timer0 (FIO4) and Timer1 (FIO5) so that you can verify the operation of the input period measurement feature set up on Timer1. If desired, the wire between Timer0 and Counter0 can be maintained to test both the PWM and the period measurement feature at once.
   
   With a wire attached between Timer0 (FIO4) and Timer1 (FIO5), you should see the "Scaled" value next to Timer1 reading out approximately 1/732 (0.001366) seconds if it is properly tracking the 732Hz PWM.
   
   The Timer1 "Value" entry should always read exactly 65536 during this test since Timer0 and Timer1 use the same clock; a rising edge occurs exactly every 65536 clock cycles when Using PWM16 and the period measurement feature "Value" entry is the number of clock cycles measured between rising edges.
   
   If you do not see the proper values, ensure your wire is firmly screwed down into the Timer0 and Timer1 terminals and otherwise check your timer/counter configurations for errors.
   
   Also note that the timers have an edge rate limit of approximately 30,000 edges/s, so we do not expect input capture features such as period measurement to properly capture PWM or other signals with frequencies higher than 30,000Hz. See the timer operation performance notes.
   
   
    
6. Troubleshooting a Period Measurement Input.
   
   See the troubleshooting guidance in step 8 of our basic Timer Configuration tutorial.
   
   If the measured period is too short, this suggests extra edges are being detected. If the signal is very noisy it can cause multiple fast edges rather than a single edge. A simple low pass RC filter (e.g. R=1k and C=0.01uF gives a cutoff frequency of 16kHz) is a possible solution, but the problem suggests the signal is very noisy and could be a symptom of improper connection. Mechanical switch signals can be susceptible to signal bounce, which can result in additional edges; see the guidance in our Switch Signal app note.
   
   If the measured period is too long or returning 0, this suggests that edges are not being detected. This often means the signal is not switching between logic low (values less than 0.8V) and logic high (values greater than 2.0V) or the signal frequency may exceed the edge rate limits of the timer. See the timer operation performance notes.

Next Step:

See step 9. in our Timer configuration tutorial to save timer/counter configurations and afterwards you can move on to Logging Timers/Counters.