FTDI Unknown Device Issue - Page 1
Forum section: electronics / projects

author: Kaxsp
author_rank: Contributor
timestamp: January 12, 2015, 01:15:53 pm
content: Hi,I have an issue related a USB and FTDI component, the RS232RQ.DatasheetIt is not recognized by Windows or Linux, it says on Linux "Ftdi device not responding to set address". I installed every FTDI driver but it continous not working. The design is the following one.So, i am thinking that the issue could be that i am doing something wrong with the FTDI driver, or on the design, or the component is not working or it is wrongly solded. Do you have any idea what could be?At first, i thought that the issue could be the RESET pin, but on the datasheet it says clearly that it could be connected to VCC.So, i am quite lost here. Any help would be useful.Thank you

author: Maxlor
author_rank: Frequent Contributor
timestamp: January 12, 2015, 01:40:41 pm
content: if you runlsusbon Linux, and the device shows up with an address of 0000:0000, it'll have been affected by the windows driver FTDI put out late last year that kills fake chips.

author: DanielS
author_rank: Frequent Contributor
timestamp: January 12, 2015, 01:43:24 pm
content: My first guess is fake FTDI chip as well and the drivers simply refuse to talk to it.

author: Skimask
author_rank: Super Contributor
timestamp: January 12, 2015, 01:55:23 pm
content: Quote from: Kaxsp on January 12, 2015, 01:15:53 pmSo, what other options are there?A) Something wrong with the FTDI driver....CheckB) Something wrong with the design...CheckC) Component not working...CheckD) wrongly "solded"...CheckE) Profit???...Check

author: Kaxsp
author_rank: Contributor
timestamp: January 12, 2015, 02:06:08 pm
content: Thank you for your answers. I read on Google the problem with fake FTDI, but i discard it because i bought the component onDigikeyand it is hard to beleive that they would distribute fake components.Does anybody sees any error in the schematic that i am not seeing? If it is correct i will consider that it is badly solded (i already checked it, but who knows, it is a small pcb) or the component is defective.Thank you

author: nctnico
author_rank: Super Contributor
timestamp: January 12, 2015, 02:12:06 pm
content: Post the output of dmesg after plugging it in. That should tell a lot.

author: David_AVD
author_rank: Super Contributor
timestamp: January 12, 2015, 08:39:33 pm
content: I don't see the two 47pF capacitors you have on the D+ and D- lines on the FTDI datasheet.Also the reset pin says "connect to Vcc" (5V I assume), but you have connected it to VccIO (3.3V).

author: Monkeh
author_rank: Super Contributor
timestamp: January 12, 2015, 09:11:53 pm
content: Well, let's see your layout, and some good photos of the assembled board.Quote from: David_AVD on January 12, 2015, 08:39:33 pmThe 47p caps are standard on FTDI cables and modules (see their own cable and module schematics). Reset is internally pulled up (to vcc, most likely, but this should be on the order of 200k+), threshold max is 1.9V, should be irrelevant.

author: Psi
author_rank: Super Contributor
timestamp: January 13, 2015, 12:06:43 am
content: Quote from: Monkeh on January 12, 2015, 09:11:53 pm+1

author: Kaxsp
author_rank: Contributor
timestamp: January 14, 2015, 01:07:25 am
content: Quote from: nctnico on January 12, 2015, 02:12:06 pmHere is the output of the dmesg. Previously i executed:> modprobe usbserial> modprobe ftdi_sioI will post some photos of the board tomorrow. Thank you all.

author: Kaxsp
author_rank: Contributor
timestamp: January 14, 2015, 04:24:07 pm
content: Also, I tried to run the command lsusb to see if the Product ID was set to "0000" (as I understand that would be the case if it were a fake device) but the device didn't appeared listed.

author: Monkeh
author_rank: Super Contributor
timestamp: January 14, 2015, 04:31:45 pm
content: That's because, as clearly spelled out, it is not enumerating.

author: wraper
author_rank: Unknown
timestamp: January 14, 2015, 04:33:44 pm
content: Are you sure that your 47pf capacitors are really 47pf?

author: Monkeh
author_rank: Super Contributor
timestamp: January 14, 2015, 04:38:53 pm
content: Quote from: wraper on January 14, 2015, 04:33:44 pmWell technically the schematic does say 47 petafarads.

author: Monkeh
author_rank: Super Contributor
timestamp: January 14, 2015, 05:38:49 pm
content: Quote from: DiligentMinds.com on January 14, 2015, 05:30:10 pmUhm, no, the #RESET pin is exactly what it says: An active low reset pin. It has nothing to do with the internal power supply. The 3.3V supply for the USB interface is generated by the internal regulator, not an external divider, and is sourced out of the 3V3OUT pin for decoupling, VCCIO supply, and external use. The tolerance on that, btw, is 3.0 to 3.6V. #RESET does not even need to be connected as it is internally pulled up.4k7 over 10k, btw, would create 3.4V (outside your 'fairly accurate' range) out of 5V, and as much as 3.74V over the full allowable VBUS range. That divider is simply a method of providing a VBUS sense for self-powered operation, as this chip does not have any other input for that.Now, let's wait for the OP to actually post a layout and some photos of the assembly so we can have a shot at figuring out what's actually going on.

author: nctnico
author_rank: Super Contributor
timestamp: January 14, 2015, 09:02:49 pm
content: Quote from: Kaxsp on January 14, 2015, 01:07:25 amI'd check whether the D+ and D- lines aren't crossed. IIRC you could get these kind of effects if that is the case. The 47pf capacitors could be the culpritts as well. I've only seen capacitors on 12Mbit designs but even then they are usually 22pf or so.

author: Kaxsp
author_rank: Contributor
timestamp: February 06, 2015, 11:38:28 am
content: Sorry for the delay. This is the layout. Could it be an issue? It has two layers and D+ and D- both go in the bottom layer before connect the FTDI.

author: David_AVD
author_rank: Super Contributor
timestamp: February 06, 2015, 01:34:17 pm
content: Have you tried removing the 47pF caps ? As I said (back on page 1), they are not shown in the reference designs in the data sheet.

author: Kaxsp
author_rank: Contributor
timestamp: February 06, 2015, 05:27:49 pm
content: Quote from: David_AVD on February 06, 2015, 01:34:17 pmActually, i don´t think it would be an issue, my design is based on this design which is a cable ftdi to serial.http://dlnmh9ip6v2uc.cloudfront.net/datasheets/BreakoutBoards/ft231x-breakout-v01.pdf

author: David_AVD
author_rank: Super Contributor
timestamp: February 06, 2015, 09:42:00 pm
content: So you'd rather not spend 5 mins testing to see if that's the problem?Different FTDI chips use slightly different input circuitry. Why not just use it as per the data sheet?

author: georges80
author_rank: Frequent Contributor
timestamp: February 06, 2015, 10:54:57 pm
content: Quote from: Kaxsp on February 06, 2015, 11:38:28 amThe layout is not particularly good. You have the dp/dm crossing under what looks like ground plane several times. You have impedance mismatches. You did read the ftdi app note that regarding layout?? Likely not your problem here, but certainly something to fix on a future rev. I would suggest you route high speed differential pairs as per the app not (no cut planes on the other side of the traces, traces not near 'noisy' sources etc etc. This is of course even more critical if this was a high speed USB chip versus only full speed.Have you measured actual voltages on the PCB? Verified you don't have shorts in your soldering etc? How about a picture of the assembled board versus a pretty picture from the cad program...Regarding Reset, it is referenced to VCCIO and that is why the data sheet has the pullup/down divider from Vbus - to get close to 3.3V from nominal 5V so as to not overpower the ESD diode on the Reset pad to VCCIO.Not sure why you connected Reset to VCCIO, it states to either leave disconnected or wired to the resistive divider. Might not cause any issues, but at least follow the datasheet recommendation.I'd remove the 47pF caps at least while testing.cheers,george.

author: Psi
author_rank: Super Contributor
timestamp: February 06, 2015, 11:03:23 pm
content: Are you sure you're supposed to have pin 4 on the USB socket shorted to GND.All my designs using a FT232RL have pin 4 left unconnected and i've never had this issue.eg1 POWER2 DATA3 DATA4 NOT CONNECTED5 GNDI maybe wrong to do this (i've not checked) It was just something i noticed looking at your PCB.

author: David_AVD
author_rank: Super Contributor
timestamp: February 06, 2015, 11:27:25 pm
content: Quote from: Psi on February 06, 2015, 11:03:23 pmI wondered the same thing when I first saw the schematic, but haven't used a 5 pin socket myself so wasn't sure.A quick Google search shows pin 4 to be to do with OTG, etc. ThisMaxim pagehas some info, but I'm sure there's more details out there.

author: Psi
author_rank: Super Contributor
timestamp: February 06, 2015, 11:29:28 pm
content: I seem to remember pin 4 being used for USB OTG cables.