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Hantek DSO2xxx schematics
morgan_flint:
--- Quote from: pcprogrammer on October 17, 2022, 12:12:25 pm ---...The fact that the scope hangs when a USB to serial interface is connected, probably has to do with the boot loader. I have seen this happen on a Lichee nano too, when I was playing around with linux on a F1C100s. Not sure why this happens. Was in the time I was starting with the reverse engineering of the FNIRSI-1013D. Did not investigate it further since the FNIRSI scope does not use linux.
But good to know this, because I was thinking of integrating a CH340 USB to serial module in the scope, but if it would need to be connected to a PC to allow the scope to start is not what one wants :palm:
--- End quote ---
Just in case my memory was teasing me, I've just checked and it effectively hangs if powered on with the serial to USB not connected to the PC
I've also verified that if you connect it to the PC with the scope "hanged", the dialog that appears is the same that when you hit a key at the beginning of the boot procedure to stop it (see attached images, first one connecting USB after powering the scope and the second one keeping a key pressed during boot) so yes, it's the boot procedure that stops when USB is not connected (apparently this is equivalent to hit a key...).
Finally, this also may happen because the CH341A in my adapter is powered from the USB, not from the scope. I'll make an experiment on this and report back.
EDIT: Done! Tried powering up the scope with the CH314A connected to TX, RX and 3.3V but not to the PC and it didn't hang. I tested it three times because in one of the tests it also booted OK without 3.3V... maybe some loose connection or something, but most times it hangs on boot when TX and RX are connected to unpowered CH341. So maybe you can integrate the module into the scope as long as it's powered from the scope. I don't know if this will bring new problems when connecting USB to the PC with the scope on (of course, the module would have to be modified, removing the 5V to 3.3V regulator, for example)
EDIT 2: The CH341A module I'm using is the one known as "CH341A Mini Programmer (Black Edition)", modified for 3.3V interface
pcprogrammer:
--- Quote from: DavidAlfa on October 17, 2022, 03:51:31 pm ---Also check there's a tiny via just over R32, in the trace going to the CPU.
It must be going somewhere else, your schematic seems to be lacking this.
I checked that back in the day, but can't remember, perhabs it also goes to the fpga reset pin (RECONFIG)?
--- End quote ---
It might well be that I missed that. I will see if I can trace it on the photos I have of the PCB. Not going to open up the scope though if it is not doable from the photos :)
pcprogrammer:
--- Quote from: morgan_flint on October 17, 2022, 05:06:04 pm ---I've also verified that if you connect it to the PC with the scope "hanged", the dialog that appears is the same that when you hit a key at the beginning of the boot procedure to stop it (see attached images, first one connecting USB after powering the scope and the second one keeping a key pressed during boot) so yes, it's the boot procedure that stops when USB is not connected (apparently this is equivalent to hit a key...).
--- End quote ---
This verifies what David wrote. A simple fix could also be to just ad a pull up resistor to the RX line without powering the module. But this is something for later to test.
Still very busy with the reversal of the FNIRSI FPGA.
morgan_flint:
--- Quote from: pcprogrammer on October 17, 2022, 06:55:52 pm ---
--- Quote from: DavidAlfa on October 17, 2022, 03:51:31 pm ---Also check there's a tiny via just over R32, in the trace going to the CPU.
It must be going somewhere else, your schematic seems to be lacking this.
I checked that back in the day, but can't remember, perhabs it also goes to the fpga reset pin (RECONFIG)?
--- End quote ---
It might well be that I missed that. I will see if I can trace it on the photos I have of the PCB. Not going to open up the scope though if it is not doable from the photos :)
--- End quote ---
Attached there is a photo of the bottom side of the PCB in that zone. Apparently, that via is not connected in the bottom side... Has this PCB intermediate layers?
pcprogrammer:
Hi morgan_flint,
for as far as I know it is just a double layer PCB. I just checked it on the photos I used during the reverse engineering and found the same as you. Here is a capture from what I have with also the via marked where the trace continues in the direction of the MCU.
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