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The entrepreneur in me loves this idea. They are able to turn dishwashers into a subscription model. I love the reverse engineering even more. A really step by

The entrepreneur in me loves this idea. They are able to turn dishwashers into a subscription model. I love the reverse engineering even more. A really step by step process, very well written. However I don't understand this specific step here - "So my plan now is to read what's inside the EEPROM. It seemed that a special connector is needed, but after rummaging around the parts bin, I found that it fits into a USB-A female socket just fine! Although I had to insulate the metal case so it won't short on the PCB contacts." Can anyone that understands explain how the EEPROM board can be plugged into a USB socket? Are they similar or is there some overlap? Once its inserted do I use USB protocol to read the data? This is the most interesting part of the whole thing for me. Wish the author explained this more, even if in a separate blog.

nadavami 6y ago
It looks like the connector just happens to fit so it's only being used to make the electrical connection. The 4 pins are actually power, ground and I2C data and clock. Edit: Here https://github.com/dekuNukem/bob_cassette_rewinder/blob/master/resources/pics/pmm.jpeg https://github.com/dekuNukem/bob_cassette_rewinder/blob/mast... you can see the white and red wires coming from the USB connector labelled as SDA and SCL.
sgtnoodle 6y ago
The EEPROM board uses pads on its PCB to create an "edge connector" with 8 pads. Apparently only 4 pads are needed, and presumably there are twice as many for redundancy. Physically, the PCB happens to fit into a USB socket with close enough spacing to make good contact. This isn't surprising, because it's a very common trick to make USB plugs out of PCBs. Electrically, it's not USB though. It's two pins for power, and two for I2C clock and data. It might happen to have the same voltage and pin mapping for power as USB, though, so plugging in to a USB port on a computer might not blow anything up. A microcontroller with a USB host port might even be able to bit-bang I2C over the appropriate pins, but that would be rather clever...
mjg59 6y ago
As others have said, it's not speaking USB - it just happens to be the same shape. But it's probably not a coincidence that it's compatible with a USB socket. In this case the designer wanted a socket that had 4 pins and could be hotswapped fairly regularly. USB sockets satisfy those criteria, are cheap and are easily available. It's pretty common to find standard connectors re-used for other purposes in the embedded world (I've found SATA connectors in some extremely strange places), so it wouldn't surprise me if tearing down this dishwasher did reveal an actual USB socket.

nadavami 6y ago

It looks like the connector just happens to fit so it's only being used to make the electrical connection. The 4 pins are actually power, ground and I2C data and clock. Edit: Here https://github.com/dekuNukem/bob_cassette_rewinder/blob/master/resources/pics/pmm.jpeg https://github.com/dekuNukem/bob_cassette_rewinder/blob/mast... you can see the white and red wires coming from the USB connector labelled as SDA and SCL.

sgtnoodle 6y ago

The EEPROM board uses pads on its PCB to create an "edge connector" with 8 pads. Apparently only 4 pads are needed, and presumably there are twice as many for redundancy. Physically, the PCB happens to fit into a USB socket with close enough spacing to make good contact. This isn't surprising, because it's a very common trick to make USB plugs out of PCBs. Electrically, it's not USB though. It's two pins for power, and two for I2C clock and data. It might happen to have the same voltage and pin mapping for power as USB, though, so plugging in to a USB port on a computer might not blow anything up. A microcontroller with a USB host port might even be able to bit-bang I2C over the appropriate pins, but that would be rather clever...

mjg59 6y ago

As others have said, it's not speaking USB - it just happens to be the same shape. But it's probably not a coincidence that it's compatible with a USB socket. In this case the designer wanted a socket that had 4 pins and could be hotswapped fairly regularly. USB sockets satisfy those criteria, are cheap and are easily available. It's pretty common to find standard connectors re-used for other purposes in the embedded world (I've found SATA connectors in some extremely strange places), so it wouldn't surprise me if tearing down this dishwasher did reveal an actual USB socket.