Popular PWM generator XY-LPWM has a small, but heavily packed LCD display:
driven by Holtek HT1621 LCD Controller, driven by Nuvoton N76E003 - 8051 based MCU.
This MCU runs on 16 MHz internal RC oscillator and provides 18 KB Flash ROM, 1 KB SRAM, 18 I/O pins supporting two UARTs, SPI , I2C, 6 channel PWM and high resolution 12-bit 8 channel ADC. Sounds very interesting to hack into.
Unfortunately out of box only Keil and IAR supported as development tools. But with Small Device C Compiler (SDCC) happily compiling for 8051 MCUs for years it can be fixed quite easily.
So here it is: Nuvoton N76E003 SDCC BSP.
With this BSP it is quite easy to make XY-LPWM display serial port friendly, just compile and upload xy-lpwm-lcd example, connect the board to UART at 38400 baud and type
> lcd @0GoodByte