Colibri iMX6ULL and Custom Viola Board

Hello,
I am designing a custom carrier board for Colibri iMX6ULL using viola board reference design. I don’t require most of the pins as given in Viola Carrier board. I have few queries which are listed below:

  1. Is Viola Board is compatible with Colibri iMX6ULL? I have one viola board which I want to use for initial testing and booting of Colibri iMX6ULL.
  2. I have completed schematics of our custom carrier board. We have used Viola design as reference. Can someone validate my design?
  3. We don’t require most of the pins as given in Viola reference design. Have a look at Page numbers 6, 9, 10 and 11. I just want to be sure that I haven’t missed out any of the important pins.
  4. I am using only USBC. So, pins like USB_OC, USB_P_EN are pulled-up using resistors. USB_C_DET has been connected to voltage divider network. Check Page number 6 of my custom board.
  5. I am given access to UART_A and UART_B only in connectors. Check page 9 of my schematics.
  6. On Page no 10 of viola design, there is a note on bottom right side of the page. That note doesn’t list iMX6ULL. I am not sure what resistors to be connected in case of iMX6ULL. I have also excluded TAMPER pins as given on the same page.

You can find my schematics over here.

EDIT:

I have few more queries.

  1. Can I add sliding switch for Recovery Pin (SODIMM_PIN 91)?
  2. Can I add push button switch for RESET_EXT#? Does it require de-bouncing circuitry?
  3. Will JTAG access be beneficiary?

Thanks for your comment @satyan.raj.

Sure, Let us know if you have any further questions.

@satyan.tx I have edited my question to include few more questions. Please check.

Please find the details below:
Can I add sliding switch for Recovery Pin (SODIMM_PIN 91)?

you can use a tactile or slide switch connected to recovery pin.

Can I add push button switch for RESET_EXT#? Does it require de-bouncing circuitry?

Yes, you can use a tactile switch for RESET_EXT# signal. We have not provided any debounce circuit on Colibri carrier board and it works fine. So, I can say it not required in general. You can use a simple RC circuit for debounce circuitry.

Will JTAG access be beneficiary?

You will probably not require JTAG, as in worst case module can be recovered using USB client port. You can place the pogo pins and JTAG header on your design if you require and leave it unassembled.

Regards,
Satyan

@satyan.tx The RESET_EXT# is an input to colibri module iMX6ULL. You can check datasheet of iMX6ULL module (Page 24 | bottom). RESET_OUT# is the output pin.

Check this image

Are you familiar with Carrier Board Design Guide? https://developer.toradex.com/carrier-board-design/carrier-board-design-guides

hi @abhiarora,

Sorry, I had made my previous reply based on the RESET_OUT signal. Have updated my previous reply. Please have a look.

Let me know if you have any questions.

Regards,
Satyan Raj

@alex.tx Yes I have read it. Just want to be sure about things.

I have few more questions. You can find them here: https://www.toradex.com/community/questions/22745/colibri-imx6ull-design-review-and-questions.html
Please help guyz

Hi @abhiarora,
Please refer to the comments below:

Is Viola Board is compatible with Colibri iMX6ULL? I have one viola board which I want to use for initial testing and booting of Colibri iMX6ULL.

You can use Viola with Colibri IMX6 ULL for your initial testing. Viola carrier boards are designed to be compatible with products in Colibri family, so feature only specific to one Colibri module may or may not be supported.

I have completed schematics of our custom carrier board. We have used Viola design as a reference. Can someone validate my design?

Please refer the attached schematics PDF for our recommendation.

We don’t require most of the pins as given in Viola reference design. Have a look at Page numbers 6, 9, 10 and 11. I just want to be sure that I haven’t missed out any of the important pins.

Leaving those pins unconnected should not be an issue.

I am using only USBC. So, pins like USB_OC, USB_P_EN are pulled-up using resistors. USB_C_DET has been connected to voltage divider network. Check Page number 6 of my custom board.

Should work fine. Please refer the attached schematics PDF for our recommendation.

I am given access to UART_A and UART_B only in connectors. Check page 9 of my schematics.

No problem. I would recommend you to keep UART_A for debugging purpose and use UART_B and UART_C for the application.

On Page no 10 of viola design, there is a note on bottom right side of the page. That note doesn’t list iMX6ULL. I am not sure what resistors to be connected in case of iMX6ULL. I have also excluded TAMPER pins as given on the same page.

The note doesn’t include iM6ULL because iMX6WULL module is designed after Viola carrier. You might not need those resistors (connected to SODIMM_81 / 55 / 63 / 65 / 69). you can just leave the pull-up and pull-down resistors unassembled on your custom carrier board.

Viola schematics with comments

Regards,
Satyan

@satyan.tx. Thanks for the comment. It is of great help. Can you review some more questions that I have?

Hello @satyan.tx,
I have mailed you my design files. One more thing, you have mentioned a comment for SD card ïn your file Viola schematics with comments. I am not able to understand it. Can you help again?

Hello @satyan.tx, my SD connector is 1140084168. Can you verify my card detection circuit?. Find the latest schematics here.
This is my schematics

Hi @abhiarora,

Card detect circuit switch details are not described properly in the SD card datasheet.
As per my understanding, please refer the attached image for card detect circuit.
SD Card detect Circuit

You should get a SD card holder and test the detect circuit before adding them to your design.

Best Regards,
Satyan

Hello @satyan.tx, I have tested the holder with multi-meter. The two pins of the holder will get short if the card is inserted and will remain open if card is not inserted. However, the card holder used in original reference design of viola board works similarly. You circuit makes sense to me but the design given in reference design of viola board doesn’t make sense to our team. The two pins in the reference design of viola board are shorted in the PCB. I am not sure why?

Hi @abhiarora,

If you read the datasheet of the SD card holder (used on Viola) and look into details about the pins and position, you can understand how it works.
Hint: on Viola, Pin 9 of SD card holder is connected to SHIELD signal.

In your case, the same circuit can work if you connect CD1 to GND and use CD2 pin only for the detect signal. The same circuit can work.

Regards,
Satyan Raj

Oh. I must have missed out “Pin 9 connected to Shield” part. Thanks for clarification.