Jeffrey's Log

Hardware hack for Phoenix-MDK

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Please don’t forget to read this post before coming here.

For the newly developed Phoenix-MDK, I suggested few hardware modifications. Among them was the hardware modification for resetting the Phoenix-MDK through software i.e the user doesn’t have to press the reset button on the board to load a new program. I copied the design of software resetting from Arduino project.

The plan was to reset the controller using two pins i.e there was a pin (RTS) coming from the FTDI chip connected via a 100Kohm resistor to the reset pin of the ATMega32 and also a pin (DTR) from FTDI chip connected via a 100Kohm resistor to the PD2 pin of ATMega32. The two 100Kohm resistor was for current limit. So when the user wants to flash a software, he has to hold the PD2 down (because bootloader will wait for code from serial port only if this pin is low), send LOW pulse on RESET. Then Avrdude loads the code, take PD2 high and then send a Reset pulse again.

When I checked the Arduino design, they were only using the RESET pin to load the software using Avrdude. Arduino bootloader loaded the code in the following manner – Send a reset pulse. The bootloader will wait for the software from serial port . If the data is coming, then they will write the flash memory using that data or else they will jump to the main code. The greatest advantage over here was of using only one pin (DTR) of the FTDI chip to load the software.

I adapted the same design to the Phoenix-MDK. Now The other pin (RTS) need not be used i.e the DTR pin of FTDI chip was connected to the RESET pin of ATMega32 via 100nF capacitor. So we saved one pin (PD2) of ATMega32 which is not used in the new design.

The below python code can flash code to Phoenix-MDK (written by Pramode).
import serial, time
import os, sys
fd = serial.Serial(port='/dev/ttyUSB0', baudrate=19200)
print fd
fd.setDTR(1)
time.sleep(.1)
fd.setDTR(0)
cmd = 'avrdude -b 19200 -P /dev/ttyUSB0 -pm32 -c stk500v1 -U ' + sys.argv[1]
os.system(cmd)

Usage:
1) Save the above code as load.py
2) Write the code which you want to run on ATMega32 and Compile the code using avr-gcc.
avr-gcc -mmcu=atmega32 -Os filename.c
3) Convert a.out to hex file
avr-objcopy -j .text -j .data -O ihex a.out a.hex
4) Load the hex to Phoenix-MDK
python load.py a.hex

Update: I will soon upload the pics of newly developed Phoenix-MDK .