JBDynamics
Posts: 6
Joined: Tue Sep 25, 2018 2:11 pm
Location: Denver, CO, USA

SDIO on CM3

Thu Sep 27, 2018 7:05 pm

I know there are some threads related to this topic, but I want to be sure I get the correct answer.

I have 20 CM3 Modules that I would like to repurpose for a new project. This project requires I2C, SPI, WiFi (SDIO), Bluetooth (UART), a second UART for programming a MCU, and a SD Card for large file storage.

My issue is with SD. I have read that SD0 is used by the CM3 for eMMC, is this correct or does it use the SDX pins which are all marked as NC for the CM3? If this is the case, does this leave both SD0 and SD1 on the GPIO open for use, or is SDX still using SD0?

If SDX is SD0, then I will have to use a On Semi FSSD06 (http://www.onsemi.com/PowerSolutions/pr ... ?id=FSSD06) to multiplex SD1. I just wanted to check double check before I spend the time creating a footprint, symbol and MCAD for an FSSD06 multiplexer. However, this limits it to using WiFi or the SD card; both can not be used simultaneously with any multiplexer I've found.
Last edited by JBDynamics on Sun Sep 30, 2018 4:20 am, edited 1 time in total.

JBDynamics
Posts: 6
Joined: Tue Sep 25, 2018 2:11 pm
Location: Denver, CO, USA

Re: SDIO on CM3

Sun Sep 30, 2018 3:41 am

After re-reading the documentation, it is clear that SD0 does not support SDIO, and is connected to either the eMMC (CM3) or SDX_x signals (CM3L). Therefore, I can answer my own question; I'm left with using the CM3L instead of the CM3. I will be using the SDX_x pins to connect a uSD card and SD1 to connect the WiFi module over SDIO. Since the SD0 interface is proprietary to Broadcom and does not support SDIO, I don't know if I could use a 32GB or 64GB 4-bit data bus eMMC IC; Broadcom may have the interface locked to be compatible with only the 4GB eMMC on the CM3, so as to prevent individuals from rolling their own eMMC boot devices.

fruitoftheloom
Posts: 17603
Joined: Tue Mar 25, 2014 12:40 pm

Re: SDIO on CM3

Sun Sep 30, 2018 8:28 am

JBDynamics wrote:
Sun Sep 30, 2018 3:41 am
After re-reading the documentation, it is clear that SD0 does not support SDIO, and is connected to either the eMMC (CM3) or SDX_x signals (CM3L). Therefore, I can answer my own question; I'm left with using the CM3L instead of the CM3. I will be using the SDX_x pins to connect a uSD card and SD1 to connect the WiFi module over SDIO. Since the SD0 interface is proprietary to Broadcom and does not support SDIO, I don't know if I could use a 32GB or 64GB 4-bit data bus eMMC IC; Broadcom may have the interface locked to be compatible with only the 4GB eMMC on the CM3, so as to prevent individuals from rolling their own eMMC boot devices.

FYI NEC use a 16GB eMMC CM3:

https://www.nec-display-solutions.com/p ... ODEL.xhtml
Adieu

John Westlake
Posts: 84
Joined: Thu Nov 09, 2017 4:34 am

Re: SDIO on CM3

Sun Sep 30, 2018 5:28 pm

JBDynamics wrote:
Sun Sep 30, 2018 3:41 am
Broadcom may have the interface locked to be compatible with only the 4GB eMMC on the CM3, so as to prevent individuals from rolling their own eMMC boot devices.
We use a 16GB eMMC with the CM3Lite..... and have used bigger devices on the lab bench - so I can answer that its not "Locked" to 4GB devices.

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