# Cannot find DTA S40 via serial/usb connection **URL:** \ **Category:** DTAFast S-Series\ **Created:** [April 3, 2026, 9:10pm UTC](https://forum.realdash.net/t/cannot-find-dta-s40-via-serial-usb-connection/10164 "2026-04-03T21:10:26Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Fred1](https://forum.realdash.net/letter_avatar_proxy/v4/letter/f/e99b99/32.png) [@Fred1](https://forum.realdash.net/u/Fred1)\ **Post date:** [April 3, 2026, 9:10pm UTC](https://forum.realdash.net/t/cannot-find-dta-s40-via-serial-usb-connection/10164/1 "2026-04-03T21:10:26Z")
Desperate for some help here… Samsung galaxy tab s connected to DTA S40 via prolific serial cable, plus good quality usb to micro usb otg. DTA set as per; > [@How to connect to DTAFast S-Series ECU](https://forum.realdash.net/t/how-to-connect-to-dtafast-s-series-ecu/82/1): > > - Serial Data Output for Dash > - RS232 Data Stream: ON > - Number of Header Bytes: 4 > - Header byte values: 255, 255, 255, 255 Realdash cannot find the ecu in garage connections! It did once very briefly, first time with a new micro usb otg cable however i unplugged to change water temp settings on the laptop, now nothing, on 3 separate otg cables. On that note, with same cable this connects instantly to the laptop! I have no idea, tried everything I can think of and this is now one of the last pieces stopping a new rally car build completing, it was meant to be easy, any help much appreciated! ---
**Author:** ![realdashdev](https://forum.realdash.net/user_avatar/forum.realdash.net/realdashdev/32/6_2.png) [@realdashdev](https://forum.realdash.net/u/realdashdev)\ **Post date:** [April 7, 2026, 10:01am UTC](https://forum.realdash.net/t/cannot-find-dta-s40-via-serial-usb-connection/10164/2 "2026-04-07T10:01:47Z")
Hard to say for sure, but for me this sounds like lack of permission to use that USB device with RealDash. Check if there is a permission popup behind the app (yes, sometimes it happens) when you connect the USB. ---
**Author:** ![Fred1](https://forum.realdash.net/letter_avatar_proxy/v4/letter/f/e99b99/32.png) [@Fred1](https://forum.realdash.net/u/Fred1)\ **Post date:** [April 7, 2026, 7:28pm UTC](https://forum.realdash.net/t/cannot-find-dta-s40-via-serial-usb-connection/10164/3 "2026-04-07T19:28:41Z")
I occasionally have a pop up to allow realdash permission to use usb, not every time I attempt connection however. It seems to make no difference when I allow permssion!! ---
**Author:** ![realdashdev](https://forum.realdash.net/user_avatar/forum.realdash.net/realdashdev/32/6_2.png) [@realdashdev](https://forum.realdash.net/u/realdashdev)\ **Post date:** [April 10, 2026, 10:15am UTC](https://forum.realdash.net/t/cannot-find-dta-s40-via-serial-usb-connection/10164/4 "2026-04-10T10:15:30Z")
Again, hard to say remotely what could be an issue. If you want to spend some time with it, you could send a debug log for analysis: [How to send a debug log - General / Frequently Asked Questions - RealDash Forum](https://forum.realdash.net/t/how-to-send-a-debug-log/949) ---
**Author:** ![Fred1](https://forum.realdash.net/letter_avatar_proxy/v4/letter/f/e99b99/32.png) [@Fred1](https://forum.realdash.net/u/Fred1)\ **Post date:** [April 15, 2026, 8:22pm UTC](https://forum.realdash.net/t/cannot-find-dta-s40-via-serial-usb-connection/10164/5 "2026-04-15T20:22:57Z")
I am convinced its a usb permisions issue. I think the prolific driver app and realdash wont share the usb!! I am unable to get a debugging file bigger than 1kb! There has to be something obvious I am missing here? ---
**Author:** ![Fred1](https://forum.realdash.net/letter_avatar_proxy/v4/letter/f/e99b99/32.png) [@Fred1](https://forum.realdash.net/u/Fred1)\ **Post date:** [April 19, 2026, 8:58pm UTC](https://forum.realdash.net/t/cannot-find-dta-s40-via-serial-usb-connection/10164/6 "2026-04-19T20:58:17Z")
Knew it was something simple, all resolved, we’ll put it down to user error!!