We designed a custom imx6 board, based on the MCIMX6QP-SDB. All of the critical interfaces of the processor are intended to be identical to the kit.
We have a properly formatted and configured SD card. When we plug in this SD card to the kit and apply power, we start seeing the console output immediately and the board starts booting.
However, when we plug the same SD card in to our custom board, we see no activity. Here is a list of things that we did and some other details:
- Our board sinks approximately 300mA of current when turned on. All supply rails appear to be functioning correctly.
- Our board is designed to be booted by way of GPIO pins, so our BOOT_MODE[1:0] is '10'
- Other than that, the only 'high' boot mode config pins are, CFG1_6 and CFG2_4, the rest are all zeros.
- Just like the kit, our POR_B signal goes high a few ms after GEN_3V3 is generated.
- We confirmed that the boot mode config pins are stable before POR_B is asserted.
- As can be seen from the Boot settings, the board is configured to boot from SD3. Upon applying power, there is some initial activity on the SD3 CLK pin (at around 347 khz). The activity goes on for about 40ms. Then the CLK activity stops and we see no further progress.
- We tested the above on multiple assembled boards.
Any ideas why SD Card read may be stalling after the first 40ms of activity?