Week 4 - Electronics Production

in this week assignment is to make AVR ICSP programmer

ICSP stands for in circuit serial programming

it uses SPI pin of a microcontroller to pragram it .. this is common AVR icsp pins:

icsp pins

in this page i’ll show my attemps to make AVR programmer using both Attiny45 and Attiny44 microcontrollers

Fab Tiny star - mini:


  • Attiny45 -> microcontroller
  • 1KΩ resistor -> current limit led
  • 1.5kΩ resistors -> pull-up resistor for data -
  • 500Ω resistors -> current limit led
  • 49Ω resistors -> current limit - protection for pins
  • 3.3v zener diodes -> 5v usb to 3.3v mcu Input pins
  • red LED -> 1x power + 1x data blink
  • 100nF capacitor -> decoupling for mcu
  • 2x3 pin header -> programming header

pcb design


to start with i downloaded traces and outline cut png files of fab tiny star mini:

milling rml as you can see the following in the settings:

  • diameter 0.4 mm which is the drill-bit size 164
  • offset i set this to 1 with this bit as it will cut only once to save time and drill life
  • intensity goes from 0 to 1 which the program extinguish between black and white .. i prefer the default 0.5 which is in middle between black and white
  • z(mm) is how much the machine moves in z-axis to cut .. for milling i prefer 0.1mm when the z-axis calibrated well..

after setting the path parameters .. i set the right corner parameters (jog, speed, x,y): i set speed to 3mm x and y really depend on where i place the PCB to i always calibrate that moving the drill to the corner of PCB

Milling PCB using Ronald Modela MDX-15


i set temperature of the solder iron to 300-350 celsius degree i soldered SMD components before but very few times, here is the progress of soldering the components in GIF image..

solder steps Note: used imagemagick to create gif image although it stick in second frame, i dont know why..

note:pictures were taken by digital microscope which is really cool ..


to program the microcontroller we need a programmer which basicly convert the usb protocol to the icsp .. to flash the compiled program we use Avrdude which talks to the programmer

in order to make the program i just downloaded fts firmware v1

there are several commands in the make file and it well documented: make file

so i just compiled and flashed the mcu flash hex set the fuses: make fuses

after all of that i just unplugged the programmer and the new programmer ..
but i couldnt find it in the usb list using lsusb ..
when i check dmesg it shows that the device is “low speed” ..
i looked into the solder in Dmm using continuety test nothing seems wrong in the connection ..
i thought that its because the make file uses the f_cpu of 16.5 MHz which doesnt seems right ..
so i tried to upload blink 1 sec program …

int main()
     DDRB = 0b00010000;
    for(;;){                /* main event loop /
        DBG1(0x02, 0, 0);   / debug output: main loop iterates */
    PORTB ^= 0b00010000;

the blink was working which means the problem is not in clock speed…

so i know the problem source is not in clock speed .. or fuses that are related to the clock
when i was testing different things i did used this command
make rstdisbl

which set High fuse to 0x5D
which basicly disables the reset pin in order to use it for the mcu as io pin ..
i couldnt program it again later after i discovered what i ve done …

disable reset fuse

Start over:

i really couldnt find the issue so i started milling different circuit .. followed same procedures .. and flashed the MCU .. set the fuses .. had the same problem but then i did also redid the soldering for the USB pinout and tried again and i got it running..

What was wrong?

i am not sure why it did not work the first time i made it. i followed the exact same way the second time and it worked. but i have a guess. the attiny i used the first time was from a batch that was in the lab since 2015 (i checked the date on the bag) and the bag it was in was open. i think maybe it is possible that the microcontroller i used the first time was damaged becuase it is really old and was exposed to air moist. the second time i used a newer attiny that we just ordered from digikey so maybe that could be the reason it worked.