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Topic: bootloader on atmega328p-pu, USB FTDI Bitbang (Read 3208 times) previous topic - next topic

Cue2

Dec 11, 2012, 04:14 pm Last Edit: Dec 11, 2012, 04:19 pm by Cue2 Reason: 1
Hi everyone, I'm new here

I also have little experience with electronics so I thought I'd start out by building a breaduino. I've scoured the internet trying to learn and while putting it together I encountered several problems which I cannot find answers to.

My breadboard looks like this

So I have two questions

1) Am I right in thinking that if I connect the FTDI basic to the black header directly below it on the breadboard a reverse-bias will destroy my 5V regulator?

2) More importantly, is it possible to burn the bootloader on to the blank atmega382p with the FTDI basic alone?

retrolefty

Quote
So I have two questions

1) Am I right in thinking that if I connect the FTDI basic to the black header directly below it on the breadboard a reverse-bias will destroy my 5V regulator?

Well something might get destroyed, but most likely the FTDI basic module. The Spark fun schematic for the FTDI basic says it's default wiring option is set for 3.3vdc and wiring that to your +5vdc power bus on your breadboard is sure to be dramatic for the FTDI module! Simply don't use a jumper wire connecting the FTDI's power pin to your breadboard, just leave it unconnected. Also you should modify the FTDI basic to utilize +5vdc signals rather then it's default 3.3v signal levels, the FTDI basic schematic shows where you can cut  a trace and solder a different trace option to force the FTDI to use +5vdc signal levels.

http://www.sparkfun.com/datasheets/DevTools/Arduino/FTDI%20Basic-v21-5V.pdf

2) More importantly, is it possible to burn the bootloader on to the blank atmega382p with the FTDI basic alone?

No, a FTDI basic module just creates a hardware USB serial link for the PC it's attached to. To burn a bootloader to a chip requires a hardware ICSP programmer. Note that a standard arduino board loaded with a arduinoISP sketch can perform the function of being a hardware programmer for blank chips wired to the arduino board.
Lefty




Cue2

#2
Dec 11, 2012, 06:56 pm Last Edit: Dec 11, 2012, 06:59 pm by Cue2 Reason: 1

Well something might get destroyed, but most likely the FTDI basic module. The Spark fun schematic for the FTDI basic says it's default wiring option is set for 3.3vdc and wiring that to your +5vdc power bus on your breadboard is sure to be dramatic for the FTDI module! Simply don't use a jumper wire connecting the FTDI's power pin to your breadboard, just leave it unconnected. Also you should modify the FTDI basic to utilize +5vdc signals rather then it's default 3.3v signal levels, the FTDI basic schematic shows where you can cut  a trace and solder a different trace option to force the FTDI to use +5vdc signal levels.

http://www.sparkfun.com/datasheets/DevTools/Arduino/FTDI%20Basic-v21-5V.pdf


Sorry about that, I should have made it clear that the power adaptor will not be plugged in when the FTDI basic is connected to a USB port. I also have an FTDI Basic variant with a jumper pin (no soldering, the type you find on motherboards) and have set it to 5V. However I still think that the regulator will be killed but I'm not sure. I guess one way of finding out is to just try it but what would the symptoms of a voltage regulator killed by reverse bias be? would it not pass any voltage at all anymore or would it pass an unregulated voltage?


I was thinking of replacing one wire like this so that Vcc is on the other side of the regulator.


However, I've read that a voltage regulator must be fed with a voltage slightly higher than your target (5V) so if the USB Vcc is 5V (already regulated?) then this is not wise, correct? I guess another option is a diode but I don't have any so I'm looking for an alternative.

I've read you can use the FT232RL on the FTDI basic in bitbang mode to burn a bootloader. Unfortunately all the tutorials seem dated and I can't get them to work:

http://doswa.com/2010/08/24/avrdude-5-10-with-ftdi-bitbang.html
http://www.ladyada.net/learn/breakoutplus/ftdifriend.html

The Android-IDE keeps throwing errors at me so I was wondering if anybody has had any success or if it's still possible.

retrolefty

A simple diode (1N400x) wired from input to output pins of your regulator will protect it from any 'reverse current condition'. Cathode wired to input pin.

Lefty

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