How to convert an adapter which is using usb to bluetooth? - Page 1
Forum section: electronics / projects

author: Chriss
author_rank: Frequent Contributor
timestamp: February 28, 2020, 10:26:18 pm
content: Hi!I'm curious doe this schematic is possible to convert in a way to use it with bluetooth instead of usb?http://emmd.ro/wp-content/gallery/vag-com-usb/schematic.jpgIs it possible to use something like the HC-05 or HC-06 BT module?I'm thinking to take out the ftdi ic and the rx/tx line to hook up to the BT module, but I see there is the DCD and TRS line too and on the BT module I can't see any of them.BTW. I already found another module where only the Rx & Tx pins are connected to the FT232 ic.If I would interchange the FT232 with a BT module would that maybe work?Maybe to take care about the voltage level on the Rx & Tx line on the FT232 to make it compatible with the HC-05 or HC-06 module.What do you think, how could such of interface be converted from USB to BT?Thanks for any suggestion or idea.

author: mvs
author_rank: Frequent Contributor
timestamp: February 29, 2020, 10:43:59 am
content: K/L interface has custom baudrate of 10400 baud, so you will need to set up UART speed of BT module accordingly. Firmware of chinease modules like HC05 is very limited, i doubt that you can do it via AT commands. Perhaps you could set it via CSR Programmer and PSTool directly.

author: Chriss
author_rank: Frequent Contributor
timestamp: February 29, 2020, 10:56:50 am
content: Thank you very much for this good suggestion.I'm not limited to that china bt module.Can you pls advice a good bt module what I coul use for such of experiment?Thanks.

author: mvs
author_rank: Frequent Contributor
timestamp: February 29, 2020, 11:28:07 am
content: Bluegiga (now Silabs) modules with iWRAP firmware like WT12-A-AI and Roving Networks RN41/42 (now Microchip) are quite good. Hardware in this modules is essentialy the same as in HC05, CSR BC04 Ext chipset.

author: rvalente
author_rank: Frequent Contributor
timestamp: March 02, 2020, 01:02:52 am
content: Those simple and cheap elm327 bluetooth adapters are not suitable for you?

author: Chriss
author_rank: Frequent Contributor
timestamp: March 02, 2020, 09:19:14 am
content: Hi!Thank you for your replay.The major reason why I wish to do is to learn and have fun.For dealing with cars I use most of time original diag tools but it come acros my mine why not to make such of hack/mod name it as yiu wish.Many times the ELM327 can't do thinks like the lets say VAG KK-L tool can.Let's say the elm327 can't access the airbag module in most of Italian cara but the VAG KK-L cable can do that.But that is another think...I will try to make this kind of mod and write feedback here about my progress and results.

author: rvalente
author_rank: Frequent Contributor
timestamp: March 02, 2020, 12:43:37 pm
content: STN11000, which is a enhanced version of ELM327 can work fine with k-line @ 10400 bps.But I get, you probably are using VAG or multi ecu scan, which emulate the protocol direclty on the ftdi chip. Probably a bluetooth bridge wont work, because the bt module wont interpret ftdi specific commands..OBD-Link does not work with multiecu scan, eg.You may use a "usb wireless extender".When I service my car, my scanners are also PC based (I've a Launch bluetooth adapter, as well), the best thing to me is to put the laptop in a tool cart instead of using over the lap, inside the car...

author: Chriss
author_rank: Frequent Contributor
timestamp: March 02, 2020, 05:09:16 pm
content: I didn't really understand what you wrote about the ftdi and its emulation of the k-line protocol.The ftdi is converting serial transmission to usb signals.So i don't got the idea how the ftdi could emulate anything?

author: rvalente
author_rank: Frequent Contributor
timestamp: March 02, 2020, 09:34:03 pm
content: The K-line protocol is a little funny, the 10.4K baud is not standard for many adapters, and there is some extra pulses other the classic serial port to make it work.I never used any k-linw/kwp2000 usb dongle that worked fine other then FTDI based, probably because the developers use some especial features from the chip.Take multiecuscan as example, the support for K-line is only for FT232 and very special devices, not ELM327 or obd-link, not sure why.So, resuming, I believe you'll ran into some problems to find a bluetooth serial emulator, them its easier to use the USB wireless adapters

author: DBecker
author_rank: Frequent Contributor
timestamp: March 02, 2020, 10:28:17 pm
content: Quote from: Chriss on March 02, 2020, 05:09:16 pmThe KKL interface is using the special features inside the FTDI chip, not just the generic serial Communication Device Class.The second K line is there to wake up modules using a 5 baud signal. That is generally "bit banged" in software.

author: Chriss
author_rank: Frequent Contributor
timestamp: March 02, 2020, 11:29:50 pm
content: Hmmmm....This are interesting infos.Something is still unclear.I can remember when I made the same k/kl cables with the max232 ic. That time I didn't had access to ftdi ic's and I used them on real rs232 on my laptop.Then the usb port was involved and the ftdi ic was used but the main circuit was almost the same like with the max232.On the ftdi ic only the Rx and Tx line is used and the D+ and D- of course and the pwr line too.Elm327 also can use the KL protocol and is working well.It is true does elm327 can not multiplex the KL line but it is working.So, what did I'm missing?Old kk l cable with max232 was working that time on the same fiat punto 2001. like the same kk l cable with the ftdi today.I'm not really see what and where is the difference in the protocol.20 years ago we used the max232 cos we don't had usb port on laptops and nowday they are here..

author: rvalente
author_rank: Frequent Contributor
timestamp: March 03, 2020, 11:59:17 am
content: Booth the FTDI and the native serial port bit bang some extra pulses, that why you'll run into problems to have a bluetooth module to replace, since you can't change the software...Besides that, what software are you using? vagcom?

author: Chriss
author_rank: Frequent Contributor
timestamp: March 04, 2020, 12:46:10 pm
content: I use vagcom also but many other interfaces and apps also, like MultiECU for Fiat cars etc.An interesting point for me here is does let's say I have to access the engine ecu with multiecu app and the airbag module on the same Fiat car which use the same ISO9141 K Line for both of the ecu's, elm327 can not access the airbag module but can access the engine ecu.But VAG KK-l interface can access both of them, I have just link pin7 from the interface to pin 7 on the OBD2 port in the car for engine ecu access.To access the airbag module I link the same K-line pin 7 from VAG KK-L to pin 3 in the DLC.If I do the same with let's say the ELM327, this interface can access the engine ecu but no way to access the airbag module.For first I was thinking maybe the multiECU didn't support AT commands to access the airbag module through ELM327,but reading now your post's I see maybe there is much more in the background.So, it is a bit confusing for me what's going on