AWR1642: 24-Bit SPI Frames

JeremY Ward

Part Number: AWR1642

I am trying to use the AWR1642 as a SPI master. I need to connect a SPI slave (another TI part) that uses 24 bit word SPI transfers from an AWR1642. Here is a timing diagram of the slave:

The problem is that the mmwave sdk only supports sending SPI frames of 8-bits and 16-bis (uint32_t SPI_Params_t::dataSize SPI data frame size in bits, only 8 and 16 are supported), which means the master (AWR1642) raises CS sooner the slave demands. Is there any way to get the driver to send 24 bit transactions without having to manually control the CS via a GPIO?

over 7 years ago

0 Jitendra Gupta over 7 years ago

TI__Guru 69960 points

Hello Jerem,

AWR1642 SPI peripheral supports max 16 bits of data word in one transfer.

If 23Bit is not the fixed rule for your implementation then you can use higher SPI-clock rate to match your throughput requirement.

Regards,

Jitendra

0 JeremY Ward over 7 years ago in reply to Jitendra Gupta

Prodigy 120 points

The TI SPI slave part requires CS be held low for 24-bits and then raised. There are no 23-bit requirements in either the master (AWR1643) nor slave.

I have increased the SPI-clock rate to 40MHz. The clock is 10x faster than it needs to be to meet timing. The issue is controlling the CS manually (as a GPIO) is too slow.

I need to get 24-bit transactions (CS goes low for 24-bits then high again) out of the AWR1642 without manually controlling (bit-banging) the CS as a GPIO. Can this be done in the AWR1642?

0 Jitendra Gupta over 7 years ago in reply to JeremY Ward

TI__Guru 69960 points

Hello JeremY,

As AWR1642 supports maximum 16 bits of word length in one transfer. So to work with slave HW, you can choose SPI option to reduce word length to 16 bit to match with master SPI.

Regards,
Jitendra

0 JeremY Ward over 7 years ago in reply to Jitendra Gupta

Prodigy 120 points

Your TI SPI slave only supports 24-bit transfers. http://www.ti.com/lit/ds/symlink/dac8218.pdf. The slave requirement can't be reduced.

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AWR1642: 24-Bit SPI Frames