Matrix Orbital Corp

Hi,

unfortunately I don't have a module at hand otherwise I could look this up myself.

The EVE3 module manual describes the pinout of the 20 pin FFC connector on page 8, figure 7/table 4. Pin 1 = VCC etc...
So if I use a bottom-bottom FFC cable like the mentioned WE 687620050002 and a bottom contact FPC connector like WE 68712014522 (same as on the display module), the pinout is inverted, right? So on my own PCB I have Pin 20 = VCC - correct?

This is a classic - at least one could resolve this possible mistake by changing to a top-bottom cable or a top contact connector.

Regards, Martin

Hello Martin,

Thank you for posting on the forum.

You are correct, sorry for the headache. A simple change on the part number mentioned on the manual would have made things easier (or a mention of both depending on the contact type of the connector on the host board): from Würth Elektonika 687620050002 to 687720050002 (which is top-bottom cable as you mentioned). I will make sure to have this corrected.

Thank you,
Raquel

Dear Raquel,

thanks for the clarification.
There's no mistake from your side - your documentation is correct. However, I am sure every developer using his first FFC connection falls into this trap - you put two connectors on different boards with identical pinout, connect them via cable and see the thing go up in smoke (or simply not work). This is inherent to FFC and quite obvious once you realize it. So instead of changing the WE part number (which few will notice), you could do mankind some good by adding a comment like
"Note that when using bottom-entry FPC connectors on both sides and a bottom-bottom cable, the pinout will get inverted. Change the connector pinout accordingly or to keep it, use either a top-bottom cable or a top-contact FPC connector (example: add part number here) on your PCB".

Regards, Martin

I created an account to second Martin's suggestion.

I only happened upon this post when searching for information on what pull-up resistors the EVE3 displays had... and easily could have made the same miswiring mistake on my first PCB if using the recommended connectors and cable. Since the display PCB bonds pins 19 and 20 together (both grounds), but pins 1 and 2 are VCC and GND respectively, miswiring in this way is certain to short out the user's PCB (bridging 3.3V to ground).

Martin's suggestion of adding text that explicitly clarifies the pinout and FFC orientation would save Matrix Orbital users a LOT of potential frustration (and PCB rework).

Another thing, while I'm here, is that it would be helpful to specifically clarify what pull-ups are needed. For example, your competitors seem to favor pull-ups on CS, /INT, and /PD... but I see after some digging that the Matrix Orbital EVE3 displays only have a pull-up on /INT? The schematic shows a pull-up and capacitor to ground for the reset pin, but these are marked as "Do Not Populate". And I don't see a placeholder for a CS pull-up. Explicitly clarifying the pull-ups, what is in place and what might be required for proper operation, would help people have more success with your displays, particularly anyone evaluating Matrix Orbital displays who is coming from a different vendor.

I up this post in relation with mine:
viewtopic.php?f=45&t=6916
On our custom board do we need to add pullups and series resistors on all lines for high speed SPI bitrate (1Mhz-20Mhz)?