hello, please, I flash my quad dso and the program is blocked, now dso quad blocks, no more display, I can not find how to put in DFU mode, there exist a program for reset the bios and application, please help me 
Unless you have somehow flashed over the main loader the device should still update via the normal mechanism.
So the first question is: If you plug USB into PC and then power on the device with the left hand button (RUN) held down, does the DFU disk drive appear on the PC?
If yes then just reflash the FPGA and main app hex using the standard procedures.
If no then tell us a bit more what you flashed to get into this state.
Good evening, the pc does not recognize, and I have a white screen and it does not happen in fdu, and that’s 15 days since I bought 
So then you should tell us what exactly you did want to flash (tell us the Filename!)- and
- Is it the new Version Ver 2.70 (It shows or showed the version on startup!) see this here: http://www.seeedstudio.com/forum/viewtopic.php?f=26&t=3518
- was the DSO recognized on your PC without any Problems before
- how did you try to flash?
- Have you tried on another PC/Notebook?
Here someone had the same Problem: http://www.seeedstudio.com/forum/viewtopic.php?f=26&t=4419- wonder if he solved it!? - Maybe you try to contact him anyway!
If you have really corrupted the DFU bootloader then the only way to recover is to use the STM serial bootloader to reflash that. That means taking the device apart and attaching a serial connection to the internal serial connector and using a new DFU image file. There are a few threads on this forum about how to do that.
BUT you should exhaust all the other possibilities first. E.g trying other USB hosts and also describing how you got in this state as that might help assess whether the DFU is really corrupt.
Yes I have corrupted the system but I don’t found how to make the serial cable, if you have
The draw I can make it.
In the dso there is connect serial CN7
CN7 is the right connector. The circuit schematic shows the pin out. You need to connect with TTL type serial levels. The USB serial adapters found on eBay are a convenient way to make the connection.
You need the STM32Flash utility and a suitable image to flash. These link gives more info on connections, recovery and suitable images.
Thank you for the information I have to command(order) a converter
On eBay but on the connector cn7 what does(throws) to use?
I have been operated for the hand thus I waits some day to flash dso, and with it I collect the information, thank you for your help(assistant)
I have receive this USB TTL 
ask me if just connect pins tx and rx and gnd to dso cn7
Check first post in that link
viewtopic.php?f=26&t=2519&p=9337
It tells you what to connect. In particular as well as the serial TX,RX and GND you also need to connect 1 and 2 on CN7 to put it in serial bootloader mode.
hello I have flash my dso quad think you but I haven’t license number can youe help me
I think you need to flash a special sys file which will show the License number to use based on the hardware id. There is a reference to this and the sys.zip you need at the end of the first link describing this.
thank you but I noticed that on startup it asks for the serial but you can use it without serial ,is this normal?
Yes, I believe that is normal but you’ll get the dialog each time you start up.
You can get license number with this program (assuming it’s still valid, seeed’s forum tends to replace attachments)