Converting USB back to UART - Page 1
Forum section: electronics / projects

author: tiofilo75
author_rank: Contributor
timestamp: October 05, 2013, 07:27:34 am
content: I have a BU-353 GPS receiver that I can plug to my computer and see my current position. My computer is able to recognize the device as a serial comport, so I decided to run it through putty to see if it works. Well needless to say I got a lot of random variables. The module has a PL-2303HX which convert the UART into to USB, now my question is if its possible to convert back to UART through a micro controller? I could mod it where I can tap into the TX pin before it gets converted but I want to avoid this. Thanks.

author: Psi
author_rank: Super Contributor
timestamp: October 05, 2013, 07:38:38 am
content: It is possible, yes.The quickest way would be to write some simple code on a Raspberry pi to pass the data to its real serial port. Since its linux it should already have the USB-Serial driver.Otherwise, to do it yourself on a mcu, you'd have to stuff around with USB host support and write a usb driver. It wouldn't be a very productive use of time.A mod to get at the TX/RX inside the device really is the best solution.If you want to avoid cutting holes in the case for another connector you could mount a bluetooth serial module inside. Then you can use another externally to receive the data and do with it whatever you want. Arduino etc..

author: Bored@Work
author_rank: Super Contributor
timestamp: October 05, 2013, 08:01:10 am
content: The conversion back to UART will not fix your original problem - that you get random data on the virtual com port.The PL-2303HX is transparent for the data. It just packs the serial data into USB. The virtual com port driver on your PC unpacks the data from USB and presents it to you - unaltered.If you see random data now on the virtual com port you either have somehow messed up the communication parameters or it is indeed that the device sends exactly this random data.

author: Psi
author_rank: Super Contributor
timestamp: October 05, 2013, 08:36:48 am
content: True, i assumed when he said "random variables" that he meant all the nema data variables.

author: nctnico
author_rank: Super Contributor
timestamp: October 05, 2013, 11:31:29 pm
content: IMHO the baudrate is wrong. Look at the manual of the GPS receiver and setup Putty properly.

author: eliocor
author_rank: Unknown
timestamp: October 06, 2013, 02:19:51 am
content: according to manual:http://www.globalsat.com.tw/products-page.php?menu=2&gs_en_product_id=2&gs_en_product_cnt_id=28&img_id=409&product_cnt_folder=8you have to:QuoteHave you done this? At what speed have you set putty? RTFM?

author: tiofilo75
author_rank: Contributor
timestamp: October 07, 2013, 07:40:28 am
content: O.k so my baud rate was in fact set up wrong. After I changed to 4800 it worked correctly with putty. Thanks. So I went ahead and tapped into the GPS so that I can get the TRX and was able to read the serial data. Now my problem is that I cannot get a satellite lock since I guess I was a little to brutal with the antenna. I'm new to this and initially thought that the ceramic antenna was attached with a wire to a trace but it seems that it is not the case. I'm sure I screwed up the thing but I am now curios as to how the receiver picks up the signals. I am gonna try and see if there is a way to repair the antenna so that I can get my position again. I attached some pictures of how the antenna mates with the PCB. Thanks for the help so far, anymore recommendations will be appreciated.

author: magiccow
author_rank: Contributor
timestamp: October 07, 2013, 02:20:50 pm
content: Many of the older external units (like the eTrex units) are unwanted now and turn up cheaply on ebay. You could probably get eTrex + serial cable for a comparable price to the BU-353 and save hacking it apart.

author: RMS95
author_rank: Contributor
timestamp: October 07, 2013, 06:08:56 pm
content: For your problemCheck out the datasheet, probably you have to convert the data.A while ago I saw some tutorials about bad GPS antennas, try googling a bit =)For converting back to serial(in case someone just landed on this page with Google :p)TemporaryTry hooking up an FT232 breakout board or something that does the same job. (you can mirror/echo them with your PC) That should work I guess.PermanentIn my opinion, an acceptable permanent solution, is any microcontroller with USB built in.Something like PSoC5 is quite easy to program and should do the job.The advantage of using a microcontroller is that it's smaller, more efficient and cheaper.Note that USB usually is a lot quicker than UART of course.QuoteStill, you really are turning water into wine and trying to get the water back....

author: PA0PBZ
author_rank: Super Contributor
timestamp: October 07, 2013, 06:47:15 pm
content: Quote from: tiofilo75 on October 07, 2013, 07:40:28 amWell, there is a pin and there is a hole (J1), so what else do you need to put it back together again?

author: tiofilo75
author_rank: Contributor
timestamp: October 07, 2013, 07:22:45 pm
content: QuoteI don't know, I thought that it would be just that simple but the GPS cannot get a satellite lock anymore.

author: nctnico
author_rank: Super Contributor
timestamp: October 08, 2013, 12:43:13 am
content: Its seems to me the PCB got damaged during disassembly of the receiver.