Design of the FABISP


Challenges
SInce we do not have a FAB ISP in the lab, the challenge is how to program the new FABISP. But then after abit of research, I realised that I can use the paralle port to program the FABISP. This then means that I build a parallel port programmer. The schematic is as following

Parallel port programmer

The schematic shows the connection for the parallel port to the MOSI and MISO lines of the FABISP. I used the stk200 as the interface for programming the FABISP



Parallel port programmer to program the FABISP




FabISP circuit board

My intention is to make two circuit boards. The first that I made which dint't take long to make was by use of etching. The second board is made by using the roland modela. The schematic and circuit I had to re-do by using Proteus ARES pcb software. The reason for me to re-do the circuit was because the mini usb port is not available in the lab.I was able to get a USB B connector which is now on the FAB ISP board.

FabISP circuit board




FabISP circuit board after milling




FabISP circuit board after etching




FabISP circuit board with components and USB B


FabISP circuit board






Programming the FABISP


This was the more challenging especially that there is little resources on ATTiny44. From the make file of the firmware.zip there are a couple of lines that need to be changed. For me at first I used a 20Mhz resonator which refused to work but was still able to program the Attiny44 throught the parallel port. I looked for a 12Mhz crystal oscillator from a spoilt pendrive which would let the FABISP work. The reason as to using the parallel port is that there was no other programmer.


From the make file I changed the interface to stk200 to programe the FABISP. The new line looks as following.

#AVRDUDE = avrdude -c stk200 -p $(DEVICE) # edit this line for your programmer


After changing the above line and the frequency, the FAB ISP would still not be seen because the drivers are not loaded to the FABISP. There is aline that one has to change and give the directory of the usb drivers of the ATTiny44. Once I was able to change the make file line,
cp -r ../../../usbdrv .

I change this to specify the directory of where the usbdrivers are within the firmware file.


To program,

I install AVRDUDE, then go to the directory of firmware folder in command window then I type make hex and then make program. A list of information is then displayed. The command window will also show that fuses are ok. After that I all i do is remove, short on sj1 and plug the FABISP into the usb and a pop up window appears on the tansk bar saying "found new Hardware. FABISP". Installed the drivers and FABISP is ready for use.