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Topic: Does FTDI232 chip need programming before use? (Read 13071 times) previous topic - next topic

liuzengqiang

I did some search online. Everything I saw was using existing FTDI232 breakout board to build stuff. This gives me the impression that the chip, when properly connected to USB and arduino, will need no programming and just works on a board.

I found this in its spec sheet:
Quote
Entire USB protocol handled on the chip. No USB specific firmware programming required.


I'm designing a project and decided to go from ATMEGA32U4 (after learning building bootloader) to ATMEGA328P-AU. I just need the FTDI chip like an old arduino would need it. I suppose a couple of decoupling caps and a cap between its DTR and ATMEGA328P-AU RESET will do. Am I too naive?

Sparkfun's PCB tutorial has it:

https://www.sparkfun.com/tutorials/108

Thanks.
Serial LCD keypad panel,phi_prompt user interface library,SDI-12 USB Adapter

raschemmel

Did you install the USB Windows driver and verify it shows uo in Device  Manager as COM-"n" ?

liuzengqiang

Yes but that's with an actual UNO. I have not purchased the surface mount FT232R chips yet. Just asking.
Serial LCD keypad panel,phi_prompt user interface library,SDI-12 USB Adapter

raschemmel

So you're still in the dezign phase and want to know what hardware you need to load sketches to yiur 328 with an FTDI breakoutor a discrete SMD chip ?

liuzengqiang


So you're still in the dezign phase and want to know what hardware you need to load sketches to yiur 328 with an FTDI breakoutor a discrete SMD chip ?


Thanks for trying to understand what I was doing. I want to place ft232r on my board to load sketch. I want confirmation that the Ft232r chip can be placed on my board without itself requiring to be programmed first.
Serial LCD keypad panel,phi_prompt user interface library,SDI-12 USB Adapter

raschemmel


liuzengqiang

Serial LCD keypad panel,phi_prompt user interface library,SDI-12 USB Adapter

raschemmel

#7
Sep 29, 2014, 06:15 am Last Edit: Sep 29, 2014, 06:21 am by raschemmel Reason: 1
This might answer your question:
 https://www.sparkfun.com/datasheets/IC/FT232R_v104.pdf

I don't have a YES or NO answer to your question. I'm a hardware person but I assume you know about installing the FTDI USB driver before using such a device : (see page 2 of datasheet)
http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT232R.pdf   

stratosfear

#8
Sep 29, 2014, 11:58 am Last Edit: Sep 29, 2014, 12:28 pm by stratosfear Reason: 1
The FT232 devices I've used have always worked without programming.  I switched some time ago to the FT230 for the lower cost and smaller size.  An early version of the FT230 was erroneously released in D2XX mode and had to be reprogrammed for VCP. 

Common practice these days adds a clamp diode on the Atmega's reset pin to catch negative spikes caused by the cap.  Remember to add a pullup resistor on the Atmega's reset pin, too. 

Just want to add that you should buy from reputable sources.  A few friends have been burned by counterfeits from ebay.

Jon

graynomad

It works out of the box, you probably have to load a driver (I can't remember now) but that's all. And follow the current hardware designs of which there are 1000s.

______
Rob
Rob Gray aka the GRAYnomad www.robgray.com

liuzengqiang

Thanks everyone! I will look into the diode on reset. I didn't know that. Do you mean the 100nF cap I wil add between DTR and reset creates negative voltage?
Serial LCD keypad panel,phi_prompt user interface library,SDI-12 USB Adapter

ron_sutherland

I found FTD232RL worked without programming. My schematic:
http://epccs.org/indexes/Board/RPUftdi/Documents/RPUftdi,Schematic.pdf

I also used DTR to reset the MCU. My setup may be a bit complicated, but I think it gives significant understanding. I considered using the 3V3 from the driver (RS485) chip directly. However, after going through the capacitor (C7 on my schematic) that would only take RESET down to 1V7 which is not bellow the 0V9 threshold needed. So I have to level translate DTR to 5V which can then drive RESET down to almost ground potential through the capacitor. I could have a problem with some boards (e.g. Zero), except with IOREF used on the pull up resistor I should be fine without a diode. Schematic:
http://epccs.org/indexes/Board/RPUadpt/Documents/RPUadpt,Schematic.pdf
my projects: https://github.com/epccs

stratosfear


Apparently the concern is with spikes exceeding the supply voltage, not going negative.  There's a schematic in this thread.

Jon

liuzengqiang

Thanks stratosfear! That makes a lot of sense now.

Thanks ron. Yeah, your schematic is a bit sophisticated. I will study it a bit more.
Serial LCD keypad panel,phi_prompt user interface library,SDI-12 USB Adapter

ron_sutherland

Ok now I see... so that diode does look like a good idea.

Looking at my circuit...  U4D is an open collector which will pull down fast, but the R14 will pull up slow which reduces the overshoot some (but how much I need to check). Unfortunately, the FTDI will pull to 5V fast and coupled through the capacitor make a 10V overshoot on the reset line.  Page 291 of the ATmega328 datasheet shows that 12V will put it in Parallel Programming mode, and then things get messy. I had not considered all risk with this reset trick, I even show the overshoot on my schematic.
my projects: https://github.com/epccs

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