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Author Topic: [help] rx tx pins in usbasp  (Read 3838 times)
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rahuljin
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« on: March 27, 2009, 08:07:43 08:07 »

hello,

i want to make a simple and cheap usb programmer for avr. so i think about usbasp. my problem is that what is the purpose of the rx and tx pin when all the necessary pins like miso, mosi, reset, sck, gnd and Vcc.

also, will it be able to verify the data writtern on microcontroller.

rahul
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microkid
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« Reply #1 on: March 27, 2009, 01:59:32 13:59 »

tx and rx pins are not necessary and they are not used in usbasp

usbasp is able to verify the data written in the micro

Best of luck, u have choosen a good programmer

MicroKid
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rahuljin
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« Reply #2 on: March 29, 2009, 03:25:11 15:25 »

i build the programmer but it is not working.
i have checked the fuse bits of atmega8 and using a 12 mhz crystal. every connection is OK as per the site. i install the driver libusb_0.1.12.1 since i am using the latest version of winavr and the usb is recogonised as usbasp.
the change the programmer to usbasp and port to usb. when i tried the program the microcontroller atmega16, this error shows up -----

avrdude: error: programm enable: target doesn't answer. 1
avrdude: initialization failed, rc=-1
         Double check connections and try again, or use -F to override
         this check.

i am using a 8mhz crystall with the atmega16 and it is working fine with the paraller port programmer.
please help.
the usb wire lenght is less than a meter and the wire from programmer is about 10cm.
also, checked the programmer by providing the power to the target board externally.
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microkid
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« Reply #3 on: March 29, 2009, 05:19:18 17:19 »

Hai

As you say the programmer is recogonised, then there would be no problem with usbasp.

And as atmega16 is working with PP programmer, The only problem would be your connections to target

Another thing try using slow clk option

MicroKid
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rahuljin
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« Reply #4 on: March 29, 2009, 06:31:58 18:31 »

this is how i connect the programmer's atmega8 and target atmega16 ----

atmega8                          atmega16
mosi (pin 17)  -------->   mosi (pin 6)
miso (pin 18)  -------->   miso(pin 7)
sck (pin 19)   -------->   sck (pin 8 )
oc1b (pin 16) -------->   reset(pin 9)

is it correct ?

update : there was a mirror solder mistake of mine. got it now  Cool

i also emailed fischl about the rx and tx. he told me that they are for some debugging which is the part of some other project.
« Last Edit: March 30, 2009, 03:13:29 15:13 by rahuljin » Logged
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