New Archer C20 v6. Serial and support needed


I recently got this unit. Seems almost identical to the v5 (which works perfectly fine with OpenWRT) except for the 5G Chip and the fact that this one has 4 antenas (v5 has 3 antenas).

Internally seems that 2 antenas are for 2G and the other 2 for 5G


Also, wanted to post a boot log but I'm unable to get output. Soldered the 4 pins, photos:

From right to left and far right being the one with the printed triangle im connected as follows: TX - RX - GND - empty

I've swaped TX and RX still no output. I remember back in the 940v5 that i had to bridge a resistor in order to get output but on this one I don't see where to do the same or if its needed.

I'm at 115200 speed, don't know if its correct or not.

Any help to get this bootlog via serial is very much welcome as i think its needed for devs to see if they can cook a version of OpenWRT that works as good as the previous v5


Try different speeds, 57600 is also a common baud rate. If you have an oscilloscope, you can measure the Tx pin. GND looks correct.

If you have a multimeter, check where Tx and Rx go to - the traces seem to be on the other side of the board.

Hi! Now the new v6 has also arrived at Am**on and my supply of cost effective routers has ended. @Sauztriaco were you able to get a bootlog?

Ok guys and gals, we got a bootlog!

Finally made it work, here it is: a full serial bootlog + MTD info for an Archer C20W (US1) V6!

Hey @tmomas your input would be greatly appriciated!

Wow thanks so much Sauztriaco. I see that it has an 8MB flash , and that everything is basically the same (I think), save for the 5ghz chip. So it should be a really straightforward port. I wonder if anyone can help us. Years ago, @robimarko was great help, and he mentioned that 4MB was a no-go, but this is a very important "workhorse" router for a lot of us.

And as per the bootlog, without being an expert, I think that this is basically an 8mb flash router that has everything practically the same as the TP-link ARcher c20 v 5.0 with an upgraded 5ghz media chipset.

~ # cat /proc/mtd
dev:    size   erasesize  name
mtd0: 00020000 00010000 "boot"
mtd1: 00160000 00010000 "kernel"
mtd2: 00640000 00010000 "rootfs"
mtd3: 00010000 00010000 "config"
mtd4: 00010000 00010000 "romfile"
mtd5: 00010000 00010000 "ispconfig"
mtd6: 00010000 00010000 "radio"
~ # cat /proc/partitions
major minor  #blocks  name
  31        0        128 mtdblock0
  31        1       1408 mtdblock1
  31        2       6400 mtdblock2
  31        3         64 mtdblock3
  31        4         64 mtdblock4
  31        5         64 mtdblock5
  31        6         64 mtdblock6```

Anyone knows who to tag for a possible build with this new info?

You are the one with the device, so that would, essentially, be you. Create a patch and send a PR on github or to the mailing list.

I would try booting a v5 build (or a custom build using v5 dts) as partitions there match the v6 layout except that bootloader is split into factory-uboot and boot.

It looks like you can also try booting with v4 dts (or using the v4 build directly) as the partitions match exactly but I would try backing up the flash chip first as it might replace the bootloader which might brick the device.

The only thing that won't work with the build is 5GHz wifi but if you build a v5 or v4 with kmod-mt7615e and kmod-mt7663-firmware-ap it should probably work without further changes. (except that at least in 22.03 MT7613BEN has a bug and might stop working when a station disconnects but a patch can work around this)

Then if that's the case, someone can make a new dts and build rules easily.

I still don't quite understand what's the difference between mt7628an_tplink_8m-split-uboot.dtsi (c20v5) and mt7628an_tplink_8m.dtsi (c20v4) but the latter exactly matched the flash layout of your v6.

Thank you for the detailed reply, it was very helpfull.

I can confirm a successful flash with v4 firmware!

But, just like you mentioned it, we lost 5G radio. Everything else seems to work perfect, leds included.

So a new v4 build with kmod-mt7615e and kmod-mt7663-firmware-ap is the next step.

Any info or tips is as always appreciated, I'll keep you posted!

I can confirm this v4 flashing works perfect, I just flashed, and it works. perfectly, save obviously for 5ghz. So its just a matter of adding the kmod-mt7615e and kmod-mt7663-firmware-ap modules on the buildroot?

Do i need to modify anything else, or just by adding that, it'll load that 5ghz up?

It should make 5GHz work but to make a proper build you might want to remove kmod-mt76x0e as it is not used.

I'll do just that and report back! Thanks very much

Thanks for your help! We can confirm a new build (based on v4), taking off kmod mt76x03 and adding mt7615e and mt7663-firmware. it changed wlan0 and wlan1 to phy1-ap0 and phy0-ap0, which is fine. The only question remaining would be that the LED for 5ghz is now off. Where do I edit or how do I find out how to map the GPIO to get the led indicator up and running?

That I can't help you really as I don't have the hardware:

  • the dts file is located in openwrt/target/linux/ramips/dts/mt7628an_tplink_archer-c20-v4.dts
  • there is this part that says GPIO 40 is for 5GHz... you may try changing this but I don't know the correct value
		wlan5g {
			label = "green:wlan5g";
			gpios = <&gpio 40 GPIO_ACTIVE_LOW>;
			linux,default-trigger = "phy1tpt";

Ok I'll check it out because right now

POWER - 5G - Ethernet are the ones not working. Only 2G and WAN are ok.

Is this any help from the v6 board:

cat /sys/kernel/debug/gpio
gpiochip2: GPIOs 416-447, parent: platform/10000600.gpio, 10000600.gpio-bank2:

gpiochip1: GPIOs 448-479, parent: platform/10000600.gpio, 10000600.gpio-bank1:
 gpio-453 (                    |rfkill              ) in  lo IRQ ACTIVE LOW
 gpio-454 (                    |reset               ) in  hi IRQ ACTIVE LOW
 gpio-455 (                    |green:wlan2g        ) out lo ACTIVE LOW
 gpio-456 (                    |green:wlan5g        ) out hi ACTIVE LOW
 gpio-457 (                    |green:wps           ) out hi ACTIVE LOW
 gpio-458 (                    |green:lan           ) out lo ACTIVE LOW
 gpio-459 (                    |green:wan           ) out lo ACTIVE LOW

gpiochip0: GPIOs 480-511, parent: platform/10000600.gpio, 10000600.gpio-bank0:
 gpio-482 (                    |green:power         ) out lo ACTIVE LOW
 gpio-491 (                    |orange:wan          ) out hi ACTIVE LOW

The v4 has 6 leds, the v6 has 5 leds.

The offsets in v4 dts are 416 or 480 which looks fine to me, but it's useless if it is read directly from the openwrt build. The init leds script also looks fine - it should work if you haven't changed the device model.

Is this from the openwrt build or from the factory one?

They still don't have a C20v6 in their GPL code center