Joined: 21 Jan 2017 Posts: 1779 Location: Illinois Moderator
Posted: Wed Dec 22, 2021 17:02 Post subject:
Ok, I am revising my suggested pin out and this is my thought process. Vcc is the Silkscreened arrow on the bottom On the backside of the pcb that lowest pin has a capacitor going to it...usually to provide clean power, thus why I think the silk screen is Vcc. The next pin up is likely ground since there are no traces on the back side going to this pin, Then there are two more traces which you will have to guess which is Tx and Rx and if they don't yield anything using putty then try swapping those two...
That's my best guess as to how the pins are.
A multimeter will confirm which pin is ground with an immediate and sustained beep.
VCC can be tricky, but once you found gound you will be able to find Vcc because it will beep on initial touch and then stop because of the capacitor. At least that's how I am able to confirm it on a Archer A7v5 I have open. TX and RX will never yield any continuity with a multimeter and ground.
My guess is the top pin is RX and the next pin down is Tx, just a hunch. _________________ FORUM RULES
Posted: Sun Jan 09, 2022 13:19 Post subject: continuity test
With no power applied to the router, use the continuity test (usually looks like a sideways WiFi symbol) touch the leads together. The multimeter should beep.
Now find VCC and ground using his instructions.
Find a good ground (negative of power is best, or the metal sides of the reset button. Then use the positive lead to probe the 4 pins. 1 pin will have a solid beep, that is ground. 1 pin will have a temporary beep then nothing, that is VCC. The other 2 are Tx and Rx. _________________ Before asking a question on the forums, update dd-wrt: Where do I download firmware? I suggest reading it all.
QCA Best WiFi Settings
Some dd-wrt wiki pages are up to date, others are not. PM me if you find an old one.
Netgear R7800 x3 - WDS AP / station, gateway, QoS
TP-Link Archer C7 v2 x2 - WDS Station
TP-Link TL-WDR3600 v1 - WDS Station
TP-Link 841nd v8 - NU
D-Link 615 C1/E3/I1 x 7 - 1 WDS station
D-Link 825 B1 - NU
D-Link 862L A1 x2 - WDS Station
Netgear WNDR3700v2 - NU
UBNT loco M2 x2 - airOS
Linksys EA6400 - Gateway, QoS
Asus N66U - AP
Netgear WNDR3700v3 - not used
UBNT EdgeRouter X - switch
Posted: Sun Jan 09, 2022 14:06 Post subject: Measurement with power off
With a measurement with power off, i can also identify:
pin 2 = VCC
pin 4 = GND
I used the multimeter in mode continuity test.
For the good groud i use the shields on the board.
For Pin 4 the multimeter beeps (0 Ohm).
For Pin 3 zero, no pass.
For Pin 2 a value of 207-209 Ohm, not decreasing (the same, in multimeter mode "resistance measurement")
For Pin 1 zero, no pass.
So 4=GND, VCC=2.
Pin 1 and 3 must be Tx, Rx.
What would be the next step to determine which pin is tx / rx?
I understand that if have to connect the serial ports using a USB-TLL device (i have a FT232).
Is there a documention how establish and test the serial connection.
(I have only used the USB-TTL device to flash tasmota with a special programmer.)
So i'm not certain how to do it here.
I have a mac. I tried a connection with powered on device at 115200 baud, 8N1. But i see nothing.
I have used only Tx, Rx and GND, not VCC as pointed out in a previously post.