869 PWM UART Controller
869 : PWM UART Controller
- Author: NAVEEN KUMAAR S
- Description: UART-controlled 7-channel PWM generator
- GitHub repository
- Open in 3D viewer
- Clock: 50000000 Hz
How it works
This design implements a UART-controlled PWM generator.
A UART receiver listens on ui_in[0] using a standard 8N1 protocol.
The system uses a simple two-byte command format:
- First byte selects the PWM channel (0–6)
- Second byte sets the duty cycle (0–255)
Internally, a small state machine processes these bytes and updates the corresponding duty register.
A shared 8-bit counter continuously increments from 0 to 255. Each PWM output compares this counter with its duty value:
- If
counter < duty, output is HIGH - Otherwise, output is LOW
This generates seven independent PWM signals simultaneously.
Whenever a byte is received, the UART transmitter sends back 0xAA
as an acknowledgment.
How to test
-
Connect a UART source to
ui_in[0] -
Set
ui_in[1] = 1to enable the design -
Apply reset using
rst_n -
Send two bytes:
[CHANNEL][DUTY]
Examples:
0x00 0x00→ PWM0 OFF0x01 0xFF→ PWM1 FULL ON0x02 0x80→ PWM2 ~50% duty
Observe outputs on uo_out[6:0].
Expected output: PWM signals with duty cycles matching the received values.
External hardware
- USB-to-UART adapter or microcontroller (for sending commands)
- Oscilloscope or logic analyzer (to observe PWM outputs)
No additional hardware is required.
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | UART RX | PWM0 | |
| 1 | Enable | PWM1 | |
| 2 | PWM2 | ||
| 3 | PWM3 | ||
| 4 | PWM4 | ||
| 5 | PWM5 | ||
| 6 | PWM6 | ||
| 7 | UART TX |