i.MX RT1170 First time booting failed. No JTAG, no UART.

[alex0]

We have our own custom PCB, and are currently trying to bring it up. It does not respond, and we can't tell why. I want to go over the various specialties about our PCB, then go over what we tried.

Specialties

1. We are using an external TCXO. Which is currently OFF.
2. Our eventual ROM bootloader will be FlexSPI2 NOR/NAND (Secondary Pin Group) - But FLEXSPI_PIN_GROUP_SEL is currently 0

According to the reference manual (IMXRT1170RM) - The chip has a 48MHz RC oscillator, which generates the 24MHz clock source for the chip during start-up when the external 24MHz crystal is not ready. 

We have both USB to UART and JTAG. Below is the JTAG schematic.

On the USB-to-UART bridge controller we shorted RX & TX, and see that there's no issue with the USB/UART peripherals. VDD_SOC_IN is 1V. It looks like the SoC is fully on, but we can't see anything in JTAG nor in blhost.

With JTAG: It detected the JTAG ID - 0x088C601D - which according to reference doc is the correct ID. But then says "Failed to power up DAP".

With USB-to-UART: There's no response to ping via blhost. COM port seen on Windows.

blhost -p COM4 -- get-property 0
Error: Initial ping failure: No response received for ping command.

Without these tools there's no way for us to check if the SoC is working. There should be no image, so we fully expected it to enter Serial Downloader Mode.

[Bio_TICFSL]

Hello,

The issue appears to be during initial board bring-up, with no communication established despite detecting the JTAG ID. Let me address the key points:

1. Power supply issues: While you mentioned VDD_SOC_IN is 1V (which is correct), there could be issues with other power rails. In similar cases with RT1170 processors, insufficient voltage on VDD_SNVS_DIG has prevented proper initialization of communication interfaces. This voltage should be checked as a 0.2V reading would be significantly below the required operating voltage.

2. Boot mode configuration: Verify the boot mode pins are correctly configured for Serial Downloader Mode. The i.MX RT1170 should automatically enter Serial Downloader Mode with proper boot pin configuration if no valid image is detected.

3. JTAG detection but failure to power up DAP: This often indicates a power-related issue or incorrect pin configuration. The fact that you can detect the correct JTAG ID (0x088C601D) but can't power up the DAP suggests the chip is partially operational.

4. For UART communication: Try using the sdphost tool instead of blhost when communicating with the ROM bootloader. These use different protocols and cannot be used interchangeably. The ROM bootloader and MCUBoot flashloader use different communication protocols.

5. Debugging approach:
- Verify all power rails are at appropriate voltages
- Check JTAG hardware design against the hardware design guide
- Try different JTAG speeds (100-500kHz) with J-Link commander
- Verify UART connections directly to a TTL-USB adapter without intermediary components

The detection of the JTAG ID but failure to establish full communication suggests the chip is powered and partially operational, but unable to complete the initialization process, likely due to a power domain or clock configuration issue.

Regards

[alex0]

* VDD_SNVS_DIG seems okay
* Boot mode pins are now specifically configured to be Serial Downloader Mode
* For UART - still no communication..
* For JTAG - We tried various speeds, and it still doesn't work.

Any other ideas? Additional information that could help in debugging?

[Kan_Li]

Hello @alex0 ,

Is it possible to share your schematics for a review? Looks like it can not enter Serial Download mode out of POR.

Have a great day,
Kan

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[alex0]

Hi,

Unfortunately we cannot share the full schematic, but we can share some of it. Is there anything in particular that you are curious about? Or any debug steps that would help debug the source of the problem?

You said it looks like it can not enter Serial Download mode out of POR, what would prevent it from doing so? (i.e. what checks would interfere / return false) 

I'm sharing a few of the connections that might be relevant

[alex0]

Another component approved for sharing

Is there anything we can probe to provide you with more insights?