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Altera_Forum's avatar
Altera_Forum
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13 years ago

using spi core

I want to use the spi core for adc peripheral AD9253. It has bidirectional SDIO. but spi core in nios has miso and mosi. so how do i tackle this. i want to read and write to the adc registers.
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
13 years ago

A simple solution is driving SDIO in open collector mode using a tristate i/o buffer and a pull-up resistor.

MOSI is connected to the active low buffer enable port, while the i/o buffer input is hardwired to gnd.

MISO is connected to the same i/o pin.

This way you simply put ones in the spi tx register for the bits you are supposed to receive.