I have a Raspberry Pi 3b+ successfully talking to a
Mesa 7c81, but am now trying to get it working with
a 7i90hd.  I have a very compact pcb made to go
from the 2x20 header on the pi to the 2x13 header
on the 7i90hd.  It is wired:

Signal   Rpi    7i90hd
SDI        19     13
SDO       21     15
SCK       23      11
SCS       24      17

+5V       2,4     26
GND    6,9,20,25,30,34,39         10,12,14,16,18,20,22,24

My test is:
$  mesaflash --device 7i90hd --addr /dev/spidev0.0 --spi --readhmid

Response is:
unable to set bpw32, fallback to bpw8
Unexpected cookie at 0100..0110:
00000000 00000000 00000000
No 7I90HD board found

Since a 7c81 works, it would seem my software setup is ok.
The problem would seem to lie with either my little adapter
board or with the 7i90hd.  I have a bypass cap right between
pins 4 and 6 on the RPi connector (22uF 0805 ceramic).  Do
I need to use a four layer board to have sufficient ground
plane?  I have copper pour on the top and bottom of the board,
but it did not go between pins of the connectors.

Any suggestions?

Thanks,
-- Ralph
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