3. Pulse generator

About

Mode used to generate rectangular waveform with configurable frequency and duty cycle. Can work in infinite mode or output burst of preset number of pulses.

Details

• Output configured signal at TXD pin.
• Inactive TXD pin state - LOW.
• Output voltage is 3.3V (but works with Arduino 5V logic).
• Configurable frequency (period) up to 1 MHz.
• Configurable duty cycle (pulse width).
• Output continuos signal.
• Output burst of up to 65535 pulses.
• Default settings: 10Hz, 50% duty, 5 cnt burst.

Controls

Consists of 1 main screen to activate signal output and 5 screens to set signal generator parameters.

1. ___ _ SEL - main screen. Launch continuos mode | launch burst mode | change settings.
2. 10FHZ - configure frequency (Hz).
3. 100000FuS - configure frequency in microseconds (µs).
4. 50.0d % - configure duty cycle (percentage).
5. 50000duS - configure duty cycle in microseconds (µs).
6. 5cnt - configure burst count (number).

Numerical value can be entered using button combination:

• Left SELECT, Middle SELECT - select digit to edit (indicated by a blinking segment).
• SET+, SET- - change selected digit.
• Right SELECT - jump to next parameter.

Frequency configuration

Signal frequency (pulse period) can be entered in 2 formats:

• hertz: option FHZ, between 1 and 999999 Hz.
• microseconds: option FuS, between 1 and 999999 µs.

Entered values are automatically converted between formats.
Changing value updates signal output instantly.

Example: to enter 2000Hz frequency press Right SELECT until FHZ is displayed. Enter number 2000 and go to ___ _ SEL.
Example: to enter 500µs pulse press Right SELECT until FuS is displayed. Enter number 500 and go to ___ _ SEL.

Mathematical relation between hertz and microseconds:
frequency = 1000000 / microseconds
microseconds = 1000000 / frequency

Duty cycle configuration

Signal duty cycle (pulse width) can be entered in 2 formats:

• percentage: option d %, between 0.0 and 100.0 %.
• microseconds: option duS, between 0 and FuS µs (pulse width can't be higher than period).

Entered values are automatically converted between formats.
Changing value updates signal output instantly.

Example: to enter 23.7% duty cycle press Right SELECT until d % is displayed. Enter number 23.7 and go to ___ _ SEL.
Example: to enter 500µs pulse width press Right SELECT until duS is displayed. Enter number 500 and go to ___ _ SEL.

Mathematical relation between hertz, microseconds and percentage:
frequency = 1000000 / microseconds
microseconds = 1000000 / frequency
microseconds = pulse_period_us * duty_cycle / 100

Duty cycle is a percentage 0..100% of pulse period (frequency). It specifies how long signal is in HIGH state after pulse start.
For example: If we set 400Hz as frequency (2500µs period) and want 35% time HIGH and 65% time LOW, we need to set duty cycle to: 35.0. It means signal will stay HIGH (⎽/⎺) for 875µs and then LOW (⎺\⎽) for 1625µs.

Pulse count configuration

• pulse count: option cnt, between 1 and 65535.

This mode allows to output burst of pulses (_|⎺|_) when button is pressed.
Only used when Middle SELECT key is clicked in ___ _ SEL screen.

Example waveform of 3 pulse output: ___|⎺|__|⎺|__|⎺|___

Control screen

• Left SELECT - start/stop infinite series of pulse generation with current settings. Once active, this is indicated by series of square symbols.
• Middle SELECT - start/stop finite generation of pulses, making number of pulses entered in pulse count (cnt). Once finished, indicate value goes back to a single underscore symbol. When active - incrementing percent of pulses emitted, until end.
• Right SELECT - (SEL) go back to configuration.

Enter mode:

• Select Menu > 3. PULSE.
• (deprecated) In Main screen hold Left SELECT for 3 seconds.

Exit mode:

• Open menu and select other mode.

Example

1. Enter pulse generation mode, select continuous pulse mode with following parameters:
   Frequency = 100Hz
   Duty cycle = 50%
2. Enable infinite pulse mode by pressing Left SELECT button.
3. Connect TXD pin to an LED.
4. Observe that LED lights up. Experiment by changing duty cycle and see that LED dims or brightens. Now you’ve got a working PWM module.