FT232RL Loopback FAIL - Page 1
Forum section: electronics / projects

author: tedre191
author_rank: Newbie
timestamp: July 17, 2013, 12:10:15 am
content: Hi,I just receive my pcb from OshPark for my new project and i can't get the ft232rl chip working.When I plug my board to my computer, drivers are installing and I can see the TX led light up when i'm sending data with Putty.On a loopback test, RX and TX led light up but I receive only 0x00 values back.Am I missing something ?Thanks

author: bobdagangster
author_rank: Newbie
timestamp: July 17, 2013, 12:18:57 am
content: Unless I am mistaken, it generally helps to connect the RX/TX pins on the FTDI to the MCU... (Or maybe the net names are invisible in Eagle?)

author: tedre191
author_rank: Newbie
timestamp: July 17, 2013, 12:27:33 am
content: Sorry, my mistake. Indeed, RX and TX are connected to the MCU TX and RX, names are not visible in that screenshot.To do my loopback test, I removed the MCU and connected pin 1 and 5 together. I tried with and without the two 1k resistors.

author: bobdagangster
author_rank: Newbie
timestamp: July 17, 2013, 12:50:23 am
content: Quote from: tedre191 on July 17, 2013, 12:27:33 amI was about to suggest that...CTS might want to be pulled up?

author: fcb
author_rank: Super Contributor
timestamp: July 17, 2013, 01:02:46 am
content: Download "FT_prog" from the FTDI website, have a look at how things are configured (the FT232R has onboard EEPROM).It should be trivial to join TX & RX and use something like Hyperterminal to loopback - you may have flow control setup??

author: tedre191
author_rank: Newbie
timestamp: July 17, 2013, 01:46:51 am
content: Quote from: bobdagangster on July 17, 2013, 12:50:23 amI just tried, didn't work.Quote from: fcb on July 17, 2013, 01:02:46 amFlow control is set to "None". I downloaded FT_prog and i'm able to read the FT232R EEPROM content.None of the options in "Hardware Specific" are enabeled.I'm probably missing something ..

author: David_AVD
author_rank: Super Contributor
timestamp: July 17, 2013, 01:48:29 am
content: Did you buy the chip from a known source or eBay / AliExpress? There are dodgy fakes doing the rounds if I recall correctly.

author: tedre191
author_rank: Newbie
timestamp: July 17, 2013, 03:14:24 am
content: Quote from: David_AVD on July 17, 2013, 01:48:29 amI bought the chip on eBay (2 of them, both the same issue).http://www.ebay.ca/itm/140838941057

author: richcj10
author_rank: Unknown
timestamp: July 17, 2013, 04:07:15 am
content: You got fake chips.

author: mickpah
author_rank: Regular Contributor
timestamp: July 17, 2013, 05:26:07 am
content: Quote from: richcj10 on July 17, 2013, 04:07:15 amyep very likely, I bought a board from Itead , same issue. They admitted they had been caught with fakes. They replaced it. The QC sticker must have been for the board only I guess

author: sleemanj
author_rank: Super Contributor
timestamp: July 17, 2013, 05:39:11 am
content: RTS and CTS are active LOW, either pull them down, or link RTS to CTS so it's signalling itself. Don't know if it will help, but worth a try huh.

author: David_AVD
author_rank: Super Contributor
timestamp: July 17, 2013, 06:15:41 am
content: No need to do anything with the control lines. Hooking up tx and rx is all you need for a basic connection.

author: amyk
author_rank: Super Contributor
timestamp: July 17, 2013, 10:51:34 am
content: Quote from: richcj10 on July 17, 2013, 04:07:15 amOr just defective...

author: tedre191
author_rank: Newbie
timestamp: July 17, 2013, 01:10:17 pm
content: Thanks everybody, I'm gonna buy new chips (from Digikey this time) and give them a try.

author: tedre191
author_rank: Newbie
timestamp: July 29, 2013, 05:27:43 pm
content: Just received my new chips from Newark and everything is working now. Thank you all for your help !