The manual covers all the information to change the jumpers, that is simple enough.
The problem is: are the four pads under the I2C jumpers for the 1-10K pullups required? Something is obviously needed there as they interrupt the traces to the bottom side of the I2C jumpers.
This would not be much of an issue if the manual actually indicated how they are to be filled for I2C operation.
I have done something that partially works, but an official solution or rev change to the manual would help avoid this.
LK204-7T-1U I2C Manual Ambiguity
I should elaborate
In case someone else is looking or wondering.
What I did was moved the 0Ohm jumpers to the I2C location and placed a couple of 1K5 402 resistors in the location below the jumper box.
I believe that it is possible Matrix had intended to assemble these two resistors originally and then changed their minds later. The absence of resistors in this location from the image in the manual makes it hard to tell since it is for the USB version, not serial. There is a vague reference to I2C needing 1K-10K pullup resistors, but depending on how you interpret that, people might be inclined to replace the 0Ohm jumper with a 1K-10K resistor and leave the four pads below empty.
Leaving them empty lets the line float on mine, which is why I filled them with what I believe to be the correct solution.
1) 0Ohm jumpers to select I2C
2) Pullup resistors in the space below (visibly indicated be presence and traces from the jumper pads).
What I did was moved the 0Ohm jumpers to the I2C location and placed a couple of 1K5 402 resistors in the location below the jumper box.
I believe that it is possible Matrix had intended to assemble these two resistors originally and then changed their minds later. The absence of resistors in this location from the image in the manual makes it hard to tell since it is for the USB version, not serial. There is a vague reference to I2C needing 1K-10K pullup resistors, but depending on how you interpret that, people might be inclined to replace the 0Ohm jumper with a 1K-10K resistor and leave the four pads below empty.
Leaving them empty lets the line float on mine, which is why I filled them with what I believe to be the correct solution.
1) 0Ohm jumpers to select I2C
2) Pullup resistors in the space below (visibly indicated be presence and traces from the jumper pads).
Hi NiTris,
I appreciate your question, and must apologize for the delayed response; we've had a nice couple weeks vacation from Matrix for the holidays.
First of all, it looks like you've got things working, which is great; I'll see if I can't explain why they are working.
The manual for the LK204-7T-1U is sort of an amalgamation of the serial and USB versions, so there are images for both models. However, it is rare that we include an I2C image as it is seen to be part of the serial model; this might be something we look to change.
The instructions for I2C mode seem to be rather straightforward on page 12 of the manual and I do see pull up resistors outlined in the communication section. However, you are correct, there is no mention of the resistors below the I2C pads.
This is not something we had in the past, which is why it is not in the manual. Looking at the schematics, those two pads do indeed connect the SCL and SDA lines to input power through what ever resistor is placed between them. In the past it was left to the customer to include the pull up resistors in their own circuitry, which is why the documentation is so vague.
I'll look to update that manual, and any other new products with a similar feature with an appropriate description. I'm sure our other developers will owe you a debt of thanks when the new revision is released.
Thanks,
~Troy
I appreciate your question, and must apologize for the delayed response; we've had a nice couple weeks vacation from Matrix for the holidays.
First of all, it looks like you've got things working, which is great; I'll see if I can't explain why they are working.
The manual for the LK204-7T-1U is sort of an amalgamation of the serial and USB versions, so there are images for both models. However, it is rare that we include an I2C image as it is seen to be part of the serial model; this might be something we look to change.
The instructions for I2C mode seem to be rather straightforward on page 12 of the manual and I do see pull up resistors outlined in the communication section. However, you are correct, there is no mention of the resistors below the I2C pads.
This is not something we had in the past, which is why it is not in the manual. Looking at the schematics, those two pads do indeed connect the SCL and SDA lines to input power through what ever resistor is placed between them. In the past it was left to the customer to include the pull up resistors in their own circuitry, which is why the documentation is so vague.
I'll look to update that manual, and any other new products with a similar feature with an appropriate description. I'm sure our other developers will owe you a debt of thanks when the new revision is released.
Thanks,
~Troy
Troy Clark
Design & Development
Matrix Orbital
Design & Development
Matrix Orbital