SDIO multiplexing / Prototype SPI WLAN on current GTA02

Andy Green andy at
Mon Apr 28 09:28:29 CEST 2008

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Somebody in the thread at some point said:
| Hi there,
| we played with a number of ideas on the HW side, one of them was around
| how we can extend the lifetime of gta02, by making some fixes.
| Such as removing the glamo chip. Which would leave no SDIO for the Wi-Fi
| module.

Interesting thoughts!  Removing the Glamo will be a net gain all over.

We re-used some of the S3C2442 LCD interface pins already, nothing that
can't be worked around.

What actually happens if we remove the Glamo is the WLAN is fine since
it is on the S3C2442 SDIO, but we lost connectivity to the Micro SD.  In
terms of stack complexity, it's the WLAN that will make all the trouble
so leaving the WLAN as it is sounds preferable.  But --->

| Do you have any ideas how this could be fixed, i.e. how we could remove
| the glamo on gta02 and still have Wi-Fi?
| Sean and I met Harald at the Open Hardware Summit conference, and he
| suggested this 'hack':
| Basically a form of SDIO multiplexing.
| Other options would be SPI.
| What do you think of the multiplexing, SPI, or other ways to achieve this?

One way or another we don't get it for free.

1) Move to SPI WLAN.  No glue logic needed.  Change WLAN software stack.

2) Mux S3C2442 SD.  Need glue logic.  Need to mess with SDIO drivers.
Sends out "I will make trouble" vibrations.

3) Additional SDIO chip.  Extra chip.  Low software risk.

Probably the best way to resolve this is to move to SPI WLAN, but
prototype it with the currently unused SPI bus that comes to the debug
board on current GTA02.  Then we can completely finish and prove the
worst change before we commit to it.

- -Andy
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