AT89S8252-programmer-Arduino-shield

An ISP programmer based on an Arduino Uno shield with a Python script programmer

AVRDUDE can be made to run using a modified conf file to accommodate some of the 8051-derived uCs, but the USBasp is a bigger challenge. Mainly because virtually all uCs use an active LOW RESET signals where the 8051-family uses active HIGH.

A Python script was developed by M. Tirado which can be found here https://github.com/mtirado1/at89s8252-arduino. Using a few discrete components, I made an Arduino Uno shield with a 40-pin DIL-socket to receive the target AT89S8252 to be programmed.

For the shield, I used a protoshield and used wire-wrapping to make the connections (see pics):

• Connect MISO/MOSI/SCK/RESET and GND/VCC between Uno and target DIL socket
• Connect a crystal between pins 18 and 19 (maximum 24 MHz)
• In my design, the crystal oscillator did not work very well and replaced it with a TCXO on pin 19 and leaving pin 18 not connected
• Pin 31 (EA) connected to Vcc to ensure code is run from internal program memory
• Pin 9 (RESET) with a pull-down to GND and a 10uF cap to Vcc
• I installed some headerpins and resistors so I can mount some LEDs for blinkenlights and for some testing the "blink" program.

Arduino UNO-based programmer for the AT89S8252

• Upload the "programmer.ino" sketch into the Arduino Uno.
• Connect LEDs with anode via a 220 ohm series-resistor to Vcc
• Connected LEDs with cathode to pins 1/2/3 of the AT89 and they should now blink
• Mount the target AT89S8252 into the socket on the Arduino programmer shield and the shield onto the Uno.
• Edit the config.py file:
  • Ensure the COM-port matches the port for the UNO
  • Edit the path to point the "blink.hex" file provided in the "blink" folder
  • Save and close
• Connect the programmer and in a Command Prompt, run the command "py writeprogram.py".
• This Python script will output the following information:
  • List the full path of the .HEX file that will be uploaded (as per config.py)
  • List the COM port it will use (as per config.py)
  • Your programmer responds and you see "Programmer ready."
  • It will then list the content of the .hex file
  • Upload the .hex file into the target
  • It will then ask the question to verify the upload
  • Press "y" followed by Enter to run the verification cycle.
  • You can edit script line 46 and replace it with "a = 'y'" to always verify without asking for confirmation
  • This is especially useful when calling the script from within the Keil uVision IDE
• This should have uploaded the "blink.hex" file into the AT89S8252
• If you have some blinking LED, you have confirmed all hardware and software is properly configured and connected.

For your own source code:

• Enter the source code in the uVision IDE from Keil (can be downloaded from their website for free)
• A few options must be changed from the default settings:
  • "Flash - Download" will be disabled by default. To enable, edit the following:
  • Under "Project - Options for Target - Output", ensure "Create HEX file" is ticked
  • Under "Project - Options for Target - Utilities", tick "Use External Tool for Flash Programming"
  • Under "Command", enter "py writeprogram.py" and specify the full path
  • Tick the "Run Independent"
• Edit the config.py file:
  • Ensure the COM-port matches the port for the UNO
  • Edit the path to the hex-file generated by the uVision IDE.
  • Save and close
• Press F7 in the IDE to ensure the source code compiles without errors into .HEX file
• Press F8 to compile the code and upload it using the Arduino

A few additional pointers:

• AVRDUDE does not have the config file for the AT89S8252 but there are some modified versions available on the internet
• The most basic circuit the AT89S8252 needs to operate is:
  • Supply power through GND on pin 20 and Vcc on pin 40
  • A crystal between pins 18 and 19 OR a TCXO on pin 19 with pin 18 not connected (max 24 MHz)
  • Pin 31 (EA) connected to Vcc to run code from internal program memory
  • Pin 9 (RESET) with a pull-down to GND and a 10uF cap to Vcc
• In uVision, each C-code source file must include the "reg8252.h" file for the chip-specific defines and declares
• These include pin definitions, port definitions, memory map of the registers, etc
• The oscillator frequency is 12 times higher than the machine cycle frequency (e.g. 2 MHz for 24 MHz)
• AT89S8252 instructions take 1 to 4 machine cycles to complete, making it a max. 1 MIPS chip
• For comparison, an ATMega running at 20 MHz oscillator frequency completes 20 MIPS