WROVER module with LAN8720A

zliudr
Posts: 360
Joined: Thu Oct 03, 2019 5:15 am

WROVER module with LAN8720A

Postby zliudr » Mon May 15, 2023 7:57 pm

I'm trying to put together a design with WROVER and LAN8720A. Based on existing designs such as the one with WROOM and LAN8720A, GPIO17 is used as EMAC_CLK_OUT. I wonder if there are any alternative pins for EMAC_CLK_OUT. Since WROVER uses GPIO17 for SPIRAM, if I can't use a different pin, then I'm stuck with WROOM only. It's good to know what my options are. Thanks.

username
Posts: 526
Joined: Thu May 03, 2018 1:18 pm

Re: WROVER module with LAN8720A

Postby username » Tue May 16, 2023 12:01 am

You can use GPIO0

zliudr
Posts: 360
Joined: Thu Oct 03, 2019 5:15 am

Re: WROVER module with LAN8720A

Postby zliudr » Tue May 16, 2023 1:42 am

OK thanks. GPIO0 has CLK_OUT1 feature. I'll do some tests once I have WROOM+LAN8720A dev boards in hand. Does the trace have to have some impedance matching due to 50MHz frequency?

username
Posts: 526
Joined: Thu May 03, 2018 1:18 pm

Re: WROVER module with LAN8720A

Postby username » Tue May 16, 2023 4:21 am

I did this many years ago, so I am not sure what has changes in the software. But back then you could configure to use GPIO0 as the clk.
The problem with this was that it did not allow uploading the firmware automatically. You had to manually keep GPIO0 low then reset to put it in bootloader mode for downloading. I didn't like this approach so I did it this way instead.
ESP32-WROVER v0.6.jpg
ESP32-WROVER v0.6.jpg (2.33 MiB) Viewed 2539 times

I dont use that design anymore, mainly because I only use the ESP32-S3, and there is no stock of the LAN8720A. When I need Ethernet I use the KSZ8851SNL Ethernet Controller. Works great. There is even an example to get you going here:
https://github.com/espressif/esp-idf/tr ... rnet/basic

zliudr
Posts: 360
Joined: Thu Oct 03, 2019 5:15 am

Re: WROVER module with LAN8720A

Postby zliudr » Tue May 16, 2023 1:28 pm

Thanks for sharing. I didn't check stock of LAN8720A. I guess that's another reason to not use it, besides having to rig some mechanism on GPIO0 for uploading. I'm using micropython so my support is very limited, either the LAN8720A (and a few other PHY chips I can look for stock) or wiznet W5500, which I'm struggling to make work.

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