I probably made a mistake in my first custom layout for STM32F103RE, in my SDIO lines layout to a MICROSD card :
- all my lines :
D0 up 47K, (I tried 33K too)
D1 up 47K,(I tried 33K too)
CMD up 47K, (I tried 33K and 10K too)
D2 up 47K, (I tried 33K too)
D3 up 47K, (I tried 33K too)
...are very short (< 35 mm) (I tried 33K to, and or 10K only for CMD)
- all lines on the same layer (top), with a quasi continuous ground plane on the bottom
- the ground plane is only cut for 2 vias mandatory (one for D0 and one D1)
- I placed 2 bypass capacitors (100nF and 22uF CER) near the card alimentation, and my VDD appears to be really stable.
The only "strange" thing I made : CMD line is jumped over the CLK line, with a strap jumper R0 (I tried to replace that R0 with a R22 Ohms for same results).
With this layout, the standard ST library as software for SDIO FatFs operations, and with a 4GB Sandisk class 4, I can only operate at 2MHz ??!!!
Trying from 2 to 24 MHz, I have (rarely) some random errors (especially in read operations, but not only).
So it works, but not as expected...
Unfortunately, I own only a 1 MHz bandwidth DSO Nano oscillo, so I can't confirm anything on the signal quality.
What could you advise me to fix my problems please ???