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Altera_Forum
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15 years ago

Nios2 SPI

Hi, I'm having some trouble reading from my IO expander with the SPI core from Altera :confused: Can anybody provide me with an example on how to issue a correct read to the spi inter...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
15 years ago

I send 16bits. 1 read/write bit, 7 address bits and 8 datas bits. 

void  WriteReg(alt_u8 adress, alt_u8 m_data)
{
    alt_u16 tosend;
    tosend = 0x8000 | ((adress << 8) & 0x7F00) | (m_data & 0x00FF);
    IOWR(SPI_CYCLONE3_BASE, ALTERA_AVALON_SPI_TXDATA_REG, tosend);
    while (!(IORD(SPI_CYCLONE3_BASE, ALTERA_AVALON_SPI_STATUS_REG) & 0x0020));
}
alt_u8  ReadReg(alt_u8 adress)
{
    alt_u16 tosend;
    tosend = (adress << 8) & 0x7F00;
    IOWR(SPI_CYCLONE3_BASE, ALTERA_AVALON_SPI_TXDATA_REG, tosend);
    while (!(IORD(SPI_CYCLONE3_BASE, ALTERA_AVALON_SPI_STATUS_REG) & 0x0020));
    return IORD(SPI_CYCLONE3_BASE, ALTERA_AVALON_SPI_RXDATA_REG);
}