Hello.

I am having trouble with a custom PCB using a TI Sitara AM62A74.

Software guy says he tries to enter U boot via the SD card and boot off the SD card but he 'gets garbage pretty quick' like almost immediately.

Board has the sitara, DDR4, emmc flash, PMIC. Then over 0.25mm pitch FFC cables we go to a custom programming board that has the SD card connector, some sd card circuitry, FTDI chip, USB connector, boot dip switches..

Here are some pictures of the oscilloscope when I was probing the SD lines. First set of pictures is on the progamming board. Last picture is of the clock at the mother board.

Notes: I tried my best to use the ground spring probe for these. Most parts are 01005 so it is difficult.
And really wierd, toward the end of this, Whenever I probed the clock at the programming board, I would see only 1W of consumption (normally 2W) and no clock signal. Not even touching a ground pin, just the probe (no gnd connected) still the board entered a weird mode that only consumed 1W not the normal 2W. Remove the probe and boom back to 2W.

When I went back to probing the clk line on the mother board, sure enough it still consumed 2W and would give me the clock you see.

Keep in mind that everytime I probed, I would turn power on and then capture with my oscilloscope because the only traffic on the SD lines (clk, data, CMD) happened within the first 1s or less of power up.

D1 at the programming board:

CLK at the programming board:

CMD at the programming board:

D2 at the programming board:

D3 at the programming board:

CLK At the MotherBoard:

This is the schematic from TI ( I copied part number for part number and net for net. No problem on power lines.

 

When I probe the SD clock on the programming board, the power drops from 2W to 1W, and the clock disappears, which makes me think there's a signal integrity or grounding issue. The signals look noisy, which might explain why I'm getting 'garbage' during the SD boot. I’ll check the FFC cable connections and try different probing techniques to avoid affecting the circuit. I’ll also verify the power-up timing and ensure the signals are clean across the SD lines.