Converting a Duet Wifi to a Duet Ethernet

tjschweizer · 18 Oct 2017, 18:27

I was having issues with my Duet Wifi on a University network - something about the way the traffic was routed caused me to get upload speeds around 18 kb/s. So I purchased the Ethernet daughterboard from Think3dPrint3d - they were super helpful, and it was cheaper than I expected.

Anyways, here's some pictures from the conversion. I also replaced 2 of the fan MOSFETs that I blew a long time ago. Between ordering these parts and receiving them, I blew my last MOSFET, so my Fan 3 won't work. Ah well.

Duet Wifi, Ethernet daughterboard, and MOSFETs.

My whole setup.

First I removed the bulk of the solder from the Wifi chip with desoldering braid. I absolutely love the MG Chemicals stuff.

I then heated the board up from the bottom right below the Wifi chip so I could remove it.

Removed any remaining solder on the pads and cleaned it up with an acid brush and rubbing alcohol.

Pre-tinning the holes.

A nice desoldering gun makes everything easier.

For some reason the headers that the Ethernet daughterboard came with don't fit. I pulled those out and replaced them with my own.

Fits great, just soldered it in and it works perfectly. Now the MOSFETs…

First, remove the old MOSFETs using desoldering braid.

Some solder paste

New MOSFETs in place

Done!

tjschweizer · 18 Oct 2017, 18:29

So the internet connection is perfect now. I get normal 1Mb/s upload, AJAX errors all but disappeared, and the MOSFETs work great.

I'm not sure if anyone else needs to switch to/from Wifi/Ethernet, but if you do and aren't comfortable soldering on this board let me know and we can work something out.

dc42 · 18 Oct 2017, 19:59

Nice pictures! For anyone else doing this:

I recommend you remove the SD card from its socket before doing any soldering or desoldering in that area.
On a Duet Ethernet we solder low-profile header pin strips into the Duet motherboard, then plug the Ethernet board into those. That would be why the pins didn't fit the board.

tjschweizer · 18 Oct 2017, 20:12

Thanks!

Yeah, I got some flux in the SD card socket and now it is a little sticky. I should've pulled the card out, probably would have helped. Lived and learned.

dc42 · 18 Oct 2017, 20:19

I was thinking more of possible heat damage to the SD card.

fma · 19 Oct 2017, 07:10

Thanks for this feedback. I still hesitate in switching to the wifi module+antenna, or an ethernet module…

dc42 · 19 Oct 2017, 08:05

You are right to hesitate, unless you have the proper hot air rework equipment and experience of using it.

lolorc · 19 Oct 2017, 10:02

btw, what's the max connexion speed between the ethernet module and the duet board ? I guess it uses SPI.

fma · 19 Oct 2017, 10:25

I'm not afraid of soldering/desoldering; I did this on much tiny chips

dc42 · 19 Oct 2017, 13:38

@lolorc:

btw, what's the max connexion speed between the ethernet module and the duet board ? I guess it uses SPI.

40Mbits/sec.

lolorc · 19 Oct 2017, 13:49

thanks,
in the mean time I came across https://javakys.wordpress.com/2014/10/29/the-second-trial-on-enhancing-the-throughput-of-w5500/ concluding with "To conclude, W5500 can achieve the throughput over than 13Mbps under 42MHz SPI Clock.."

dc42 · 19 Oct 2017, 14:01

Thanks for the link. I looked at using buffer sizes larger than the default 2K, however the W5500 has only 32K of buffer space total which has to be divided between the 8 possible sockets. So if you increase the buffer size on one socket, you have to reduce it on others.

I found that one of the biggest limiting factors is the speed of writing to the SD card. On the Duet WiFi I obtained 3Mbytes/sec upload speed if the Duet main processor threw the data away instead of writing it to SD card. The speeds quoted by the SD card manufacturers are for writing large blocks of data as happens in a digital camera when you take a photo. The Duet doesn't have enough RAM to write such large blocks.