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nrf: use SPIM peripheral instead of the legacy SPI peripheral
This newer peripheral supports DMA (through EasyDMA) and should generally be faster. Importantly for some operations: interrupts (within 255 byte buffers) will not interfere with the SPI transfer.
This commit is contained in:
Ayke van Laethem
committed by
Ron Evans
Ron Evans
parent
ce539ce583
commit
cda5fffd98
@@ -328,163 +328,3 @@ func (i2c I2C) readByte() (byte, error) {
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i2c.Bus.EVENTS_RXDREADY.Set(0)
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return byte(i2c.Bus.RXD.Get()), nil
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}
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// SPI on the NRF.
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type SPI struct {
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Bus *nrf.SPI_Type
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}
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// There are 2 SPI interfaces on the NRF5x.
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var (
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SPI0 = SPI{Bus: nrf.SPI0}
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SPI1 = SPI{Bus: nrf.SPI1}
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)
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// SPIConfig is used to store config info for SPI.
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type SPIConfig struct {
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Frequency uint32
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SCK Pin
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SDO Pin
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SDI Pin
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LSBFirst bool
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Mode uint8
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}
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// Configure is intended to setup the SPI interface.
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func (spi SPI) Configure(config SPIConfig) {
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// Disable bus to configure it
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spi.Bus.ENABLE.Set(nrf.SPI_ENABLE_ENABLE_Disabled)
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// set frequency
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var freq uint32
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if config.Frequency == 0 {
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config.Frequency = 4000000 // 4MHz
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}
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switch {
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case config.Frequency >= 8000000:
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freq = nrf.SPI_FREQUENCY_FREQUENCY_M8
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case config.Frequency >= 4000000:
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freq = nrf.SPI_FREQUENCY_FREQUENCY_M4
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case config.Frequency >= 2000000:
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freq = nrf.SPI_FREQUENCY_FREQUENCY_M2
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case config.Frequency >= 1000000:
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freq = nrf.SPI_FREQUENCY_FREQUENCY_M1
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case config.Frequency >= 500000:
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freq = nrf.SPI_FREQUENCY_FREQUENCY_K500
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case config.Frequency >= 250000:
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freq = nrf.SPI_FREQUENCY_FREQUENCY_K250
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default: // below 250kHz, default to the lowest speed available
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freq = nrf.SPI_FREQUENCY_FREQUENCY_K125
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}
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spi.Bus.FREQUENCY.Set(freq)
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var conf uint32
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// set bit transfer order
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if config.LSBFirst {
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conf = (nrf.SPI_CONFIG_ORDER_LsbFirst << nrf.SPI_CONFIG_ORDER_Pos)
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}
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// set mode
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switch config.Mode {
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case 0:
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conf &^= (nrf.SPI_CONFIG_CPOL_ActiveHigh << nrf.SPI_CONFIG_CPOL_Pos)
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conf &^= (nrf.SPI_CONFIG_CPHA_Leading << nrf.SPI_CONFIG_CPHA_Pos)
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case 1:
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conf &^= (nrf.SPI_CONFIG_CPOL_ActiveHigh << nrf.SPI_CONFIG_CPOL_Pos)
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conf |= (nrf.SPI_CONFIG_CPHA_Trailing << nrf.SPI_CONFIG_CPHA_Pos)
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case 2:
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conf |= (nrf.SPI_CONFIG_CPOL_ActiveLow << nrf.SPI_CONFIG_CPOL_Pos)
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conf &^= (nrf.SPI_CONFIG_CPHA_Leading << nrf.SPI_CONFIG_CPHA_Pos)
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case 3:
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conf |= (nrf.SPI_CONFIG_CPOL_ActiveLow << nrf.SPI_CONFIG_CPOL_Pos)
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conf |= (nrf.SPI_CONFIG_CPHA_Trailing << nrf.SPI_CONFIG_CPHA_Pos)
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default: // to mode
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conf &^= (nrf.SPI_CONFIG_CPOL_ActiveHigh << nrf.SPI_CONFIG_CPOL_Pos)
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conf &^= (nrf.SPI_CONFIG_CPHA_Leading << nrf.SPI_CONFIG_CPHA_Pos)
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}
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spi.Bus.CONFIG.Set(conf)
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// set pins
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spi.setPins(config.SCK, config.SDO, config.SDI)
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// Re-enable bus now that it is configured.
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spi.Bus.ENABLE.Set(nrf.SPI_ENABLE_ENABLE_Enabled)
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}
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// Transfer writes/reads a single byte using the SPI interface.
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func (spi SPI) Transfer(w byte) (byte, error) {
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spi.Bus.TXD.Set(uint32(w))
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for spi.Bus.EVENTS_READY.Get() == 0 {
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}
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r := spi.Bus.RXD.Get()
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spi.Bus.EVENTS_READY.Set(0)
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// TODO: handle SPI errors
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return byte(r), nil
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}
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// Tx handles read/write operation for SPI interface. Since SPI is a syncronous write/read
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// interface, there must always be the same number of bytes written as bytes read.
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// The Tx method knows about this, and offers a few different ways of calling it.
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//
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// This form sends the bytes in tx buffer, putting the resulting bytes read into the rx buffer.
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// Note that the tx and rx buffers must be the same size:
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//
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// spi.Tx(tx, rx)
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//
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// This form sends the tx buffer, ignoring the result. Useful for sending "commands" that return zeros
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// until all the bytes in the command packet have been received:
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//
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// spi.Tx(tx, nil)
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//
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// This form sends zeros, putting the result into the rx buffer. Good for reading a "result packet":
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//
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// spi.Tx(nil, rx)
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//
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func (spi SPI) Tx(w, r []byte) error {
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var err error
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switch {
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case len(w) == 0:
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// read only, so write zero and read a result.
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for i := range r {
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r[i], err = spi.Transfer(0)
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if err != nil {
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return err
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}
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}
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case len(r) == 0:
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// write only
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spi.Bus.TXD.Set(uint32(w[0]))
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w = w[1:]
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for _, b := range w {
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spi.Bus.TXD.Set(uint32(b))
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for spi.Bus.EVENTS_READY.Get() == 0 {
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}
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spi.Bus.EVENTS_READY.Set(0)
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_ = spi.Bus.RXD.Get()
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}
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for spi.Bus.EVENTS_READY.Get() == 0 {
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}
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spi.Bus.EVENTS_READY.Set(0)
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_ = spi.Bus.RXD.Get()
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default:
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// write/read
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if len(w) != len(r) {
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return ErrTxInvalidSliceSize
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}
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for i, b := range w {
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r[i], err = spi.Transfer(b)
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if err != nil {
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return err
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}
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}
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}
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return nil
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}
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