2024-08-08 08:53 AM
I have swapped from a custom PCB-board with a 6-layer stack using a STM32H725IGKB, to another custom board with a 4-layer stack using STM32H723ZGT6 (simpler package).
I am using an external OCTO SPI on both boards, but I have R/W errors with the 4-layer board.
Both boards are routed with 50 ohms impedance and uses 33 ohms series resistors for the OCTO SPI.
I am wondering if the output impedance is the same for these two H7-devices?
Solved! Go to Solution.
2024-08-14 01:01 AM
Many thanks tjaekel,
I believe I have reasonable “precautions steps” into consideration.
Otherwise I think I have tested everything accept for the DLYB
I am uncertain on how to measure cross-over or GND noise, do you have any tip?
2024-08-14 01:27 AM
Memory-mapped mode doesn't even work with a clock rate of 20 MHz (or anything else below the 47 MHz mentioned in the datasheet) ?
The ringing you see on the scope might come from your scope measurement itself, always use a spring tip for GND, not the usual 10cm or so GND clip.
2024-08-14 03:18 AM
Memory mapped mode works fine with OCTO SPI freq. set to 166 MHz (max for the chip) on the 6-layer board.
On the 4-layer board R/W does not seem to work even how low I set the freq.
2024-08-14 07:59 AM
Try at very low speed, 4 or even 1 MHz, to prove your design, but check with scope, the _C pins still working at all ( as I said, I killed one just by using at 16 Mbit - then it never worked again ! ). So maybe you already have a dead pin, then cannot use it to prove the design.
2024-08-15 12:05 AM
Thank you all for contributing with good ideas and advices, highly appreciated
I'll park this thread now and will go ahead with a new PCB-design without using PC2_C/PC3_C.
2024-08-29 03:46 AM
Problem solved!
It turned out to be the PC2_C/PC3_C pins that caused the faulty communication. I just received a new PCB-version of our custom board and it all works fine now using another pin assignments.
Many, many thanks for pointing this out