I have designed my own Carrier board for Colibri iMX6ULL computer-on-module. I have used Viola design as reference. You can find the schematics over here. I will be soon sending it to PCB Fab house but I have few doubts that I want to clear before proceeding further.
My questions are:
The Colibri iMX6ULL has seven 3.3V pins. However, viola reference design has only 4 decoupling capacitors? Can someone explain that to me?
Can I add Blinking LED to any pin? Do we have a provision to enable or define a blinking led pin in BSP or in any Software?
I have removed Jumper and resistor R73. I have placed a trace in place of resistor R74 (These designator belong to Viola reference design). Can someone verify my Ethernet design as I want to use only Colibri iMX6ULL board?
I have placed stitching capacitor in my design. I have placed 8 100nF 0603 caps. Any better idea on stitching caps values and placement?
I am not using Resistor Array/bank for SD and SPI interface. I don’t think it will cause any problem as long as length is matched and distance between traces is enough. Am I right?
I have added JTAG connector in my board. I am using Segger Jlink. It’s pinout is over here. You can find the JTAG connector in extension connector page. I have few questions for my JTAG design.
a. JTAG requires VREF_JTAG. Do I need to connect it to 3.3V?
b. Colibri iMX6ULL has MOD Pin. It is not required in Segger JLink Connector. What should I do with it?
c. Segger Jlink has one output pin for System Reset. I have connected it to RESET_EXT#. Is it fine?
d. I don’t have any series resistor in between JTAG connector and colibri pins. Is it fine?
e. Segger JLink connector has RTCK pin. However, iMX6ULL doesn’t have such pin. I have grounded that pin. Is it fine?
I have few more questions:
During layout and floor planning, I found out SD Card interface lines are of different length. Lines liks CMD and DATA0 are very short. Is this could be problem?
Can I remove resistors to disable PS/2 drivers and resistors to disable CF access (SODIMM PIN 81)?