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Author Topic: Another DIY FTDI cable question/help thread.  (Read 8687 times)
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Denmark
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Well, use a oscilloscope if not a multimeter, connect it to the one pad on PCB, then upload a sketch, do it one by one as soon as you see the activity on the oscilloscop or multimeter, you have find the DTR pad (the activity will apper at the same time you use to push the reset button)
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no scope..

what setting should I used on my meter to test/detect the DTR pad?


Thanks
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Denmark
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Set your multimeter to -Voltage- measuring, 0 to 10V or lower, if your multimeter has lower measuring, like 0 to 5V is also good.
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lol..(back again)

when you say I'll see 'activity' on the multimeter when I hit the rest button..what reset button? where?

should I actually have my 'hacked' FTDI cable hooked up to my breadboard/Arduino.. and upload sketches to it..thats how I shoul dbe testing? when I actually upload sketches?

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Denmark
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I didn't acctually say you have to hit the reset botton, I said you will see activity on the multimeter at the very same time that you use to push the reset botton, when you upload a sketch.

Anyway what you have to do to track the DTR pin at your 'hacked cable':
1- Connect the 'hacked cable' to the breadboard/Arduino (as you do it for uploading a sketch)
2- Set the multimeter to the Voltage measuing range and ground the multimeter to 'hacked cable' and breadboard/Arduino.
3- Connect the other prob of multimeter (red) to one of the pads at the 'hacked cable' little PCB (find a pad that has voltage)
4- Now you have to upload a sketck, and look at your multimeter to see activity.

You have to repeat the 3 & 4, with all the pads on the 'hacked cable' little print board (PCB) one by one until you have find the DTR line.

To find the DTR pad at the 'hacked cable' look after the pad which is normally high (has voltag) and become low (for a few seconds) when you upload a sketch.

The Arduino reset pin is connected to the high (5V) thru a 10K resistor, and will be reset when connected to the ground(0V) That's why the DTR line is normally high and to reset the Arduino (when uploading a sketch) the DTR must become low (0V) for a few seconds at the right moment.
When you have find the DTR line, connect it to the reset pin with a 0.1uF capacitor serial in line (look at Arduino schematic)
I hope that could help you and write back about your progress.

PS. this is not a FTDI cable, rather a Prolific's PL2303 chip, the FTDI's chip which is on the Arduino board is FT232RL  
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1- Connect the 'hacked cable' to the breadboard/Arduino (as you do it for uploading a sketch)  -CHECK
2- Set the multimeter to the Voltage measuing range and ground the multimeter to 'hacked cable' and breadboard/Arduino.  -CHECK
3- Connect the other prob of multimeter (red) to one of the pads at the 'hacked cable' little PCB (find a pad that has voltage)  -CHECK
4- Now you have to upload a sketck, and look at your multimeter to see activity.  -CHECK

this was exactly how I had done it..


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To find the DTR pad at the 'hacked cable' look after the pad which is normally high (has voltag) and become low (for a few seconds) when you upload a sketch.

this is what I was missing.. I think I was checking for it to be 'backwards'..

I was thinking when I probe'd the pads..it would state 0v..and then when I uploaded a sketch..and hit the rest button..I would see an INCREASE in voltage (hence resetting the Arduino/chip)

I have prob'd MANY pins.. most are @ 0.00v or 0.01v fluxuating..

and when I uploaded a sketch..only sometimes Id see a slight increase..but when actually TESTED to be the DTR pin/pad..didnt work.


I'll go back and look for the correct behavior now.

thanks
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Denmark
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The cable's (PL-2303 chip) output level is 3.3V, but the voltage level of DTR pin at your cable version is unknown! (it must be 3.3V, when it is not low)
Since there is many different cable version and PCB layout of PL-2303 chip, every cable hack depend on the very same kind cable and PCB layout of the different PL-2303 chip.  

A new approach:
The DTR pin Auto-Reset the Arduino (when uploading a sketch) by pulling the reset pin low (0V) that's way you are going to do the same as you did, but only this time set the multimeter to find the cannectivity. This time look after which pad/pin will be connected to ground(0V) when you are uploading a sketch, you have to be fast, it is only for a few seconds. (it would be more easy if your multimeter has a buzzer)
« Last Edit: June 25, 2010, 06:07:39 pm by mreza » Logged

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well thanks for the reply/help.. but I dont fully understand what your trying to explain to me smiley-cry

I am now confused.. if I am to be looking for a pad that by default is at 3.3v? or is at 0.0v when I meter for voltage output??

When I open the Arduino IDE.. and pick out a sketch to write.. I ground to my breadboard/Arduino.. and use the RED probe to check the open pads & vias on the pcb.

I can find 0.0v pads and anywhere from 1.6v to 5.0v on the PCB..

I if I meter some of the pads as I upload a sketch.. it looks as if 'some' of them either increase a bit or lower a bit (none go to 0v)

but when I try to hook up these pads/vias to the pin1/reset pin..  either my blinking LED (goes off..so something is wrong...and no sketches upload).. or it just doesnt reset the chip for the bootloader to accept the sketch.

Thanks
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I have had hit and miss with pin availability on the nokia data cables, but every sony erricsson one I have bought off deal extreme has had something that works for reset available on it, on the underside of the board on an unlabled pin.

I found it as described with probing and opening and closing the port to trigger it changing.

IMO the FTDI cables are better, they have a serial number in them so that you dont have the comport number change in windows depening on how things are enumerated. If you will only ever have the one device connected to the PC then the prolific ones may work for you, but I have several and I have to change things depending on when and where I plug it in on windows.
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guys.... am a newbie here... sorry for the interruption.

so u guys are saying that the pl2303 can replace the ftdi right?
well will it be ok if use the pl2303 as the ftdi replacement in the arduino 0018?

m not sure i like the darkness in the avrdude!
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If you are inexperianced, then no, get the FTDI one since its more known and suppoted. Once you have the hang of it then the cheap prolific ones are good for other things you want to do, but if you use one then you are basically trying to troubleshoot two things at once, and you wont know if its the cable or something else causing you problems.
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hi-

I have 'only' used the Arduino 0018 IDE.


I took one of these CA-42 (pl2303) data cables, soldered the wires to correct pads.. (only 3)

and then used a 'header pin' that plugs into my breadboard.

I throw my Atmel chip in the breadboard, (tons of links/tuts on how to set this up), with crystal, resistors..etc..

main thing is a RESET switch.

I open the IDE....open my sketch..

upload sketch to my chip.. as soon as I see the 'text' at bottom of IDE saying sketch size..etc..

I hit RESET button..  works every time.

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first of all... thanx guys..

most of the writings on the pl2303 demonstrates much on the usage of avrdude... which i dont quite familiar.coz i thought avrdude is the only way to go with the pl2303... heh guess i was wrong. so lets tune up the pl2303... hope it my cheap dream will come true.

by the way... ive had  experienced most of the 16 series PICs but not Atmels. i thought i was goin the cheapy way. ive just started on the Arduinos since theres so many experts in the line... so i guess it would be easy for me to learn from the best. looks like it... so far so good.

but wait... u mean its ok if we manually reset the chip without the dtr? or rts? i forgot which one was it...

thanx by the way.



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