STC15 programmator

STC programmator to upload hex firmare to MCU flash.

This repo contains kicad electrical scheme, pcb design and description of STC programmator.

STC is a family of microcontrollers with 8051 architecture.

The electrical scheme and PCB design are a Kicad files.

Table of contents

• Programmator usage
  • How to connect programmator
  • Upload firmare from Platfromio to MCU
• Electrical sheme
  • TxD-RxD part
  • VCC part
• PCB design
• Alternative path

Programmator usage

Programmator used with USB-2-TTL adapter.

CHG340g is a popular USB-2-TTL adapter.

CHG340g should be connected to PC USB port and programmator is placed between CGH340g and STC MCU.

How to connect programmator

J1 for USB adapter

• J1 +5V pin should be connected to USB adapter +5V pin.
• J1 GND pin should be connected to USB adapter GND pin.
• J1 TxD pin should be connected to USB adapter TxD pin.
• J1 RxD pin should be connected to USB adapter RxD pin.

J2 for MCU

• J2 +5V pin should be connected to MCU +5V pin.

• J2 GND pin should be connected to MCU GND pin.

• J2 TxD pin should be connected to MCU TxD pin.

• J2 RxD pin should be connected to MCU RxD pin.

  Jumper J1 is opened.

Inside programmator USB TxD is routed to MCU RxD and USB RxD is routed to MCU TxD pin.

Upload firmare from Platfromio to MCU

[Plaformio] (https://platformio.org/) is a popular embedded software development IDE based on Visual Studio Code.

Platfromio use stcgal to upload firmware.

Jumper J1 should be opened before uploading start.

1. Connect USB adapter with programmator (see How to connect programmator section). JP1 jumper should be opened.

2. Connect programmator to MCU pins. Developer boards and many PCB designs have dedicated pins.

3. Run Platfromio and open your STC project with source code that will be compiled to firmware.

4. Connect USB adapter to PC.

5. In Platfromio start upload. The most popular way to do this is press upload button

6. Platformio open terminal panel and output upload status as a messages to it

7. Waiting for "Cycling power: done" message. Uploading process waiting.

   Cycling power: done

8. Press and hold the SW1 button on the programmer until the download process is complete.

9. Uploading proccess completes with messages

Finishing write: done

Setting options: done

Target UID:

Disconnected!

10. You can release the button or hold it if you want to see how the downloaded firmware works.
11. For permanently firmware execution close J1 jumper

Electrical sheme

Scheme contains two important parts: TxD-RxD part and VCC part.

TxD-RxD part

The principle of connection between MCU and USB adapter is RxD <-> TxD. R1 and D1 are used to eliminate parasitic power supply through the pins to the microcontroller.

VCC part

The MCU is powered via USB-2-TTL adapter. MCU GND connect to USB adapter GND. USB adapter +5V connected to button SW1 and jumper JP1.

If the jumper JP1 is shorted, the microcontroller runs the loaded firmware and cannot be programmed. In firmware download mode, the jumper is open and power is supplied only when the SW1 button is pressed and held.

Capacitors C1-C3 debounce of the SW1 button. In the classic programmator scheme only one 47mF polaraized capacitor is placed. But i have only 100mF capasitors and connect it in a chain to get 50mF capacity.

PCB design

Alternative path

You can upload firmware to STC MCU with USB-To-TTL adapter only.

For this way disconnect GND wire from MCU and start firware upload. When stcgal out will be "Cycling power: done" connect GND from adapter to MCU.