RTOS/PROCESSOR-SDK-OMAPL138: TI RTOS SPI Chipselect Issue

Bhargavi Ale

Part Number: PROCESSOR-SDK-OMAPL138
Other Parts Discussed in Thread: OMAPL138

Tool/software: TI-RTOS

Hi All,

I am using pdk_omapl138_1_0_6 for LCDKOMAPL138.

I have two devices over same SPI bus (bus 1). Configuration for both the devices are different, one is in 4-pin mode and another one is in 3-pin. I tried configuring and using them at the same time and it was failing. On looking inside the spi driver it seems that at a time I can open one handle for one bus with one chip select. Meaning I cannot use both the devices at the same time.

So, is this pdk driver drawback or hardware issue?

Thanks...

over 5 years ago

0 Sahin Okur over 5 years ago

TI__Mastermind 27355 points

Hello Bhargavi,

I'm currently looking into this. I will post a reply here once I have an update.

0 Sahin Okur over 5 years ago

TI__Mastermind 27355 points

Hi Bhargavi,

Currently the driver supports one chip select per one instance of the bus. In the case of the 3-pin device, are you using an external pin for device selection?

0 Bhargavi Ale over 5 years ago in reply to Sahin Okur

Intellectual 310 points

Hi Sahin,

Yes, Am using one external GPIO to select the device.

Is the issue with software or hardware?

If I change the driver code to support multiple chip select, Will hardware works fine or not?

Thanks...

0 Sahin Okur over 5 years ago in reply to Bhargavi Ale

TI__Mastermind 27355 points

Bhargavi,

This seems like a driver limitation, see snippet from TRM:

http://www.ti.com/lit/spruh77c

0 Bhargavi Ale over 5 years ago in reply to Sahin Okur

Intellectual 310 points

Sahin,

I gone through the TRM, there I didn't find any register to configure multiple chip selects at the same time.

So, I am assuming that limitation is with hardware not with the software. Can you confirm on the same?

Thanks...

0 Sahin Okur over 5 years ago in reply to Bhargavi Ale

TI__Mastermind 27355 points

Bhargavi,

You can set multiple CS as SPI functional pins using the SPIPC0 register.

So for example, you can have one CS connected to SPI flash and the other to ADC, and based on which CS is attached the slave will respond to the data being sent.

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RTOS/PROCESSOR-SDK-OMAPL138: TI RTOS SPI Chipselect Issue