spi and rmii omap-138

Gabriel Finch

Hi,

I am developing a couple of spi drivers using the TMDSEXPL138-B experimenter board. We decided to use spi bus 1 since bus 0 is used for the flash memory on this board. Looking at the omap-138 schematics it seems that the only way to use chip selects from spi1 is to disable mii and use rmii mode to free up 2 pins. However, when I tried to configure the board for RMII mode, it was not possible to telnet to it. I believe this is because a daughter board is needed for RMII. Is this all correct ? If so, is there some other way to use spi without using rmii mode ? I believe it is possible to use gpio for the chip selects, but I think this may be too slow for our application.

over 15 years ago

0 Gabriel Finch over 15 years ago

Prodigy 50 points

I got spi1 and spi0 mixed up, but the basic question is still the same.

0 Nikolay Kokorin over 15 years ago

Intellectual 875 points

Hi Gabriel,

Yes, in your case need to use the external ethernet board with RMII.

But, I think that for you optimally way is next:

1. Use the flash memory only for boot (the E19 pin SPI1_SCSn_0 should be set to low only at booting);

2. For your driver design use same SPI1 module with any other signals of chip select (SPI1_SCSn_1 to SPI1_SCSn_7);

3. Not using SPI0 module, reserving it pins for MII interface.

Good luck

0 Gabriel Finch over 15 years ago in reply to Nikolay Kokorin

Prodigy 50 points

Hi Nikolay,

thanks for your reply. Yes I think you are right, we will have to use SPI1 which has cs 2 and 3 reserved for "external devices". I read on here that there is some way to disable the flash after booting, but I am not sure how to do so. Also /dev and /tmp are mounted in flash memory - will this not cause problems ?

0 Nikolay Kokorin over 15 years ago in reply to Gabriel Finch

Intellectual 875 points

Hi,

If you use the spi driver from PSP which support multiply instance, then all should be work is fine. But I'm not sure.

You need to make sure that only one Chip Select signal is active at the same time.

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spi and rmii omap-138