Help needed. cfe.bin for DIR-895L router

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llFawkes17ll
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PostPosted: Sat Aug 08, 2020 18:21    Post subject: Reply with quote
The serial header is not populated. I tried to find the correct pin layout by using a multimeter but I only have a cheap one so the ohms only goes to 200 rather than x1 like all youtube videos show how to find the ground. When trying to find the tx and rx the remaining pins all gave a 3.3v so I don't know which one is the correct pins for the rx and tx. I gave it try thinking that the 2nd from the right was the ground and guessed the other two. Didn't use the one I had the left. Putty serial didn't connect so I played around with the order but end it up burning the serial to usb cable. I don't know where to go from here. I don't if I should buy another serial to usb cable without knowing the correct pin layout. Also, I connected to the board by using a pin header but dint solder it in place as I don't have a soldering gun. Do you think the pin header can successfully connect to the female part of the usb cable without being soldered?


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kernel-panic69
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PostPosted: Sat Aug 08, 2020 18:45    Post subject: Reply with quote
I presume the square one on the left with the white triangle is +3.3v. The ground pin should have no resistors in line on the board traces. Hopefully, you didn't also burn up your serial interface or fry the router mainboard. It would be great if the OP would have given the information with a photo. EmbarassedRolling Eyes

I usually use the USB port shield as a reference point for ground. Only other way to test is to figure out which pin on the barrel jack for the power supply adapter is ground and then check any labeled test points to see which one(s) is/are ground.

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llFawkes17ll
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PostPosted: Sat Aug 08, 2020 19:11    Post subject: Reply with quote
I think I got lucky and only burned the usb serial cable as I am still able to read the exact values in the motherboard as before. Btw I only get 3.3v on the first pin out from the right and the third one from the right as well. So I am assuming the one in the middle of those two is the ground pin out.
Do you know if I i get the order correct if I will be able to connect without getting a soldering gun to solder the pin header in place?
kernel-panic69
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PostPosted: Sat Aug 08, 2020 19:37    Post subject: Reply with quote
You might be able to use stripped wires from the cable and push them in the holes. I prefer installing pins. So the one on the far right and far left both read +3.3v? I would assume the square one with white triangle is Vcc, and the far right one is possibly TX. Not having one of these in hand to look for myself isn't ideal. Not sure if the middle round one is GND or what, usually TX and RX have components in the trace, but ground does not.
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llFawkes17ll
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PostPosted: Sat Aug 08, 2020 20:01    Post subject: Reply with quote
The pins from the header fits on the holes of the board enough that on an angle I would assume that it would be making the same amount of contact that would be made if I stripped the wire and push them in, right?

I can't get a reading from the one with the square triangle unless if I set it to ohms 2000 on my multimeter then I get a 1008 reading. The lowest my multimeter goes on ohms is 200 and the value I get on that is 0.2.
kernel-panic69
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PostPosted: Sat Aug 08, 2020 20:48    Post subject: Reply with quote
If the square with white triangle next to the JP1 marking is reading 0.2 to ground, then it is the ground pin. BUT, if from a known good ground measuring volatge and not ohms, if it reads 3.3vdc, then it is Vcc. You are confusing the heck out of me. Generally speaking, all the ones I've put a header on, that square pad is usually the +3.3v (Vcc) pin. I removed your pic because it may be wrongly marked. Find your ground pin first with ohms reading from the USB port shield to the pins, then use voltage to find which is +3.3vdc. Your ground should read 0 volts.
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llFawkes17ll
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PostPosted: Sat Aug 08, 2020 21:18    Post subject: Reply with quote
Sorry for confusing you, as you have seen I am a noob lol. When you say to find the ground by using the usb port shield, do you mean the usb on the board? When I do that I find the ground as pin 3 (pin 1 being the white triangle).
When I have the multimeter on 20 VDC and I measure the white triangle I get no reading. I only get the 3.3V reading on pins 2 and 4 (1 being the white triangle)
kernel-panic69
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PostPosted: Sat Aug 08, 2020 21:29    Post subject: Reply with quote
In your lowest ohms range on your meter, what do you get when you have the black lead touching the onboard USB port shield (the outside metal part) on the router board and each pin? Yes, I do mean the onboard USB port, is there any other USB port on the router? WinkLaughing
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llFawkes17ll
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PostPosted: Sat Aug 08, 2020 21:35    Post subject: Reply with quote
Hahaha just wanted to make sure.
These are the readings with the lowest ohms range on my meter:
Pin 1 white triangle: 1 aka open/infinity
Pin 2: 1 aka open/infinity
Pin 3: 0.2 ohms
Pin 4: 1 aka open/infinity
kernel-panic69
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PostPosted: Sat Aug 08, 2020 21:40    Post subject: Reply with quote
Ok, from pin 3 or USB port shield, what readings do you get on pins 1, 2, and 4 in volts DC? Pin 1 should be +3.3VDC. If not, then that doesn't seem right to me, but I could be mistaken. Usually, TX and RX have resistors in-line in the board traces from what I have seen on other routers. If there is no reading at all, look for pads with no component soldered to it in-line. I know on TP-Link routers, there are some you have to get creative with to get a proper serial interface to work.

P.S. This is with power applied to the router, of course Twisted Evil

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llFawkes17ll
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PostPosted: Sat Aug 08, 2020 21:53    Post subject: Reply with quote
Meter on Volts DC with the power ON the router and the black probe on pin 3 or the usb shield I get 3.3V on pin 2 and 4 but nothing on pin 1.

I can get 3.3V with black probe from meter on pin 1 and the red probe from meter on pin 2 or 4 with the router ON of course 😈 and the meter on volts DC.
kernel-panic69
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PostPosted: Sat Aug 08, 2020 22:58    Post subject: Reply with quote
That seems wrong to me, but without a brand new one in hand to open up and check, I cannot verify. I presume you did NOT attach the +3.3v wire on your usb-uart-ttl serial cable to the router. If you did, then game over.
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llFawkes17ll
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PostPosted: Sat Aug 08, 2020 23:13    Post subject: Reply with quote
I don't think I did as I have use this specific cable once in the past and I know the four cables and what they correspond, red 5v, black ground, white Tx and green Rx.

Thanks for all the help though. I ordered another USB to TTL serial cable so I'll give it shot again. If you had to take a guess what order would you think the pins are set on the pinout? I assume 3 is ground.
kernel-panic69
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PostPosted: Sat Aug 08, 2020 23:58    Post subject: Reply with quote
I would presume if 3 is ground, then 2 and 4 should be TX/RX, unless those were the ones you tried before? I would need to see more than just where the holes are of the board perhaps, but specifically in the vicinity of it.
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llFawkes17ll
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PostPosted: Sun Aug 09, 2020 0:10    Post subject: Reply with quote
I think that order is the first one I tried but the putty window showed a bunch of weird characters. I read somewhere it else that it could have been a bad connection but by then I had played around with the order of the pins and that's when my usb to ttl cable stopped working and has a burned plastic spot where the chip is on the USB part of the cable. That's why I ordered a new one as every time I connect the USB part of the cable to the computer I get am error message "device descriptor request failed"
I took this picture before I started measuring things. Does it help?



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