An adaptor board for STC15F10x MCUs

A project log for Adventures with a STC89C52 development board

Quick way to start with MCUs

ken-yapKen Yap 08/11/2021 at 12:190 Comments

Some months ago I came across an offer of 10 STC15F104W for about 30¢ each so I took the plunge. These are 1T 8051 MCUs with 4kB flash and 128B RAM. The only drawback is it is a DIP-8 or SOP-8 device so has only 6 I/O pins but this may be sufficient for small applications, and you can always extend the I/O with serial protocols.

The datasheet was easily found with a search and In System Programming only requires Tx/Rx pins, readily available from a USB to TTL converter. But being a lazy person I wondered if I could use my QX-mini51 development board since it already has the converter on board and I have already set up stcgal.

Looking at the pinout, besides the power pins, the 6 I/O pins are port 3.0 through 3.5 with P3.0 and P3.1 used for serial communications. I just needed an adaptor. I had some prototyping boards of the right size, so I soldered a DIP-8 socket and then wires to 8 pins taken from a broken precision (round pin) IC socket. I'm feeling chuffed about not throwing that away. I don't really need P3.2 to P3.5 but I wired them anyway. I soldered another pin at 21 for better registration. Here's the result:

BTW the datasheet suggests isolation diode and resistor to prevent powering the MCU from the USB serial adaptor. This is not necessary since there is only one power supply, that feeding the QX-mini51.

I connected up the board to the USB port, ran stcgal, pressed the power switch and got this:

$ stcgal 
Waiting for MCU, please cycle power: done
Protocol detected: stc15
Target model:
  Name: STC15F104W
  Magic: F294
  Code flash: 4.0 KB
  EEPROM flash: 1.0 KB
Target frequency: 0.000 MHz
Target BSL version: 7.2.5Q
Target wakeup frequency: 35.650 KHz
Target options:

If you're wondering why the target frequency is 0, this MCU family has an onboard oscillator.

So now I have to think up of things to make with these tiny MCUs.