SerialPWM

A Microchip PIC16F used to control 4 indepedent PWM signals using basic GPIO inputs.

About

SerialPWM uses a PIC16 microcontroller to control 4 independent PWM channels. It offers an easy-to-use digital logic interface as opposed to more complex communications protocols, making it a low-cost solution for expanding PWM capability.

The SerialPWM project was developed using Microchip's MPLABX IDE and MCC Plugin, and the full project folder is supplied so it can be imported and the MCU flashed in a matter of minutes.

Signal Definitions

For a visual pinout, please refer to the /docs directory.

Inputs

SerialPWM uses an I/O sampled, GPIO interface to control the duty cycle of the PWM channels. It also offers logic to mask input commands, allowing the end-user to cascade several of these on the same board. Future enhancements are planned to enable an interrupt-driven interface.

• PWM_INH (/ Pin 10) => Chip inhibit, active-low. When high, the device will ignore all commands on the DUTY and PWMSEL pins. This allows multiple devices to share the same control lines.

• DUTY_UP (/ Pin 3) => Interrupt-On-Change (rising edge) pin that increases the current duty cycle by +5%.

• DUTY_DN (/ Pin 2) => Interrupt-On-Change (rising edge) pin that decreases the current duty cycle by -5%.

• PWMSEL0 (/ Pin 6) => PWM channel select input. The combination of PWMSEL0 and PWMSEL1 act as multiplexer control inputs which determines which of the four PWM channels the DUTY command inputs are pertinent to.

• PWMSEL1 (/ Pin 8) => See above.

Outputs

SerialPWM offers four PWM channels with indepedent duty cycles. All channels use the MCU's Timer2 module for time base reference.

• PWM0 (/ Pin 5)
• PWM1 (/ Pin 7)
• PWM2 (/ Pin 11)
• PWM3 (/ Pin 9)

Tuning Parameters

SerialPWM may have to be adjusted per application. The following defaults are used in the master branch release:

• Target MCU Pinout: PIC16LF1503
• MCU System Clock: Internal FRC, 500kHz
• PWM Frequency: 25kHz (Target frequency for ATX PC Fans)
• PWM Granularity: +/- 5% (Adjusted using the system clock)

Programming

So you're ready to use SerialPWM? Here's how!

The SerialPWM project is geared towards rapid development; users should be able to clone this repository, import the project, and be able to flash their MCU with operational code with very little, if any, changes to the original source.