I2C runt clocks

mspenard603 · ‎12-22-2020

Occasionally my iMXRT1062 will boot up in a bad mood and I'll see runt clocks on SCL. Any thoughts as to what might cause this?

Pins are configured as seen here. Slave end has 10k pull-ups as well.

jeremyzhou · ‎12-22-2020

Hi,
Thank you for your interest in NXP Semiconductor products and for the opportunity to serve you.
According to your statement, the SCL will output signals if the i.MX RT1062 doesn't boot up successfully.
I think I need to know more information about this phenomenon, so I was wondering if you can introduce the testing steps of replicating the issue and the schematic of the custom board.
Looking forward to your reply.
Have a great day,
TIC

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mspenard603 · ‎12-23-2020

Hi,

Oh, the iMXRT boots up every time. Only, sometimes, in a state where it produces I2C runt clocks.

Schematic for our board is attached.

Slave is a Cypress PSOC. It pulls SDA and SCL up to 3.3v with 10k pullups as well.

jeremyzhou · ‎12-23-2020

Hi,
Thanks for your reply.
After having a brief review of the schematic, I've not found something wrong with it.
And according to this schematic, it seems that the i.MXRT1062 boot up from the SD card.
In firstly, as I mentioned before, you need to figure out how to replicate the phenomenon, next, I'd like to know whether the phenomenon also happens on other boards.
Have a great day,
TIC

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mspenard603 · ‎12-24-2020

I suspect it might have something to do with the UART-USB bridge. Things seem to improve without debug console attached. And I always see it provide 1v from it on the 3.3v rail even when system power is off. Could you take a look at that schematic?

jeremyzhou · ‎12-28-2020

Hi，
Thanks for your reply.
1) Could you take a look at that schematic?
-- I've checked the circuit for the UART-USB bridge portion, in my opinion, it's good actually.
Did you already replicate the phenomenon on the MIMXRT1060 EVK board?
Have a great day,
TIC

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mspenard603 · ‎12-30-2020

My Eval board is heavily modified. So I'm still working on getting it ready.

My I2C issues have gone away after lifting the TX pin on the UART bridge. I think I need series current limiting resistor there. As somehow, occasionally, its keeping the MCU powered enough (the bridge was always providing 1v via this pin into the 3.3v rail). Could you 1) provide some insight on how providing current on this pin (GPIO_AD_B1_03) could be affecting I2C and/or clocking, and getting power to the 3.3v rail? Are they part of the same power group?

Also, 2), I have a possibly similar issue with SD cards getting corrupted when I flash via JTAG. Could you take a look at that schematic and see if there's any obvious reason JTAG flashing would corrupt SD cards?

jeremyzhou · ‎12-30-2020

Hi,
Thanks for your reply.
As I mentioned before, in general, the uploaded schematic is right, I'd like to suggest you check the PCB board and optimize your schematic by referring to the MIMXRT1060 board or other third party EVK boards.
Have a great day,
TIC

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mspenard603 · ‎01-01-2021

I'm looking at the iMXRT1060 schematic by NXP (attached) but I'm not seeing the UART bridge on it? Or am I blind?

My eval board is actually an Embedded Artist's iMXRT1062 eval board. It doesn't have an issue. I uses the same FTDI FT230XS as our board. Only with series resistors on TX and RX.

So it's still not clear what is going on with the iMXRT. The UART bridge is obviously providing current into the MCU, and that's the root cause. But I'm looking for an explanation on why 1v from the bridge is causing such random issues on other (I2C) peripherals. And how this 1v on TX is working its way through the MCU all the way to the 3.3v rail.

jeremyzhou · ‎01-04-2021

Hi,
Thanks for your reply.
According to your reply, the UART bridge works well on the Embedded Artists' iMX_OEM_Carrier_board, however, the UART bridge doesn't work well on your customize board sometimes, in my opinion, you can try to refer to the iMX_OEM_Carrier_board to adapt the UART bridge on your board.
By the way, whether the phenomenon happens in all your boards.
Have a great day,
TIC

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mspenard603 · ‎12-24-2020

Hi Jeremy,

Thanks for the review. It's a bare-metal app on XiP flash, SD card is only there for storage. I'm able to replicate the issue by power cycling a number of times. I'll give the app a try in the DEV EVK board.