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machine/nrf: SPI master implementation

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Signed-off-by: Ron Evans <ron@hybridgroup.com>
This commit is contained in:
Ron Evans
2018-11-30 21:34:28 +01:00
committed by Ayke van Laethem
parent 23b283366d
commit 06ab3a836f
12 changed files with 312 additions and 2 deletions
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src/machine/machine_nrf.go
+95
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@@ -232,3 +232,98 @@ func (i2c I2C) readLastByte() byte {
i2c.signalStop() // signal 'stop' now, so it is sent when reading RXD
return byte(i2c.Bus.RXD)
}
// SPI on the NRF.
type SPI struct {
Bus *nrf.SPI_Type
}
// There are 2 SPI interfaces on the NRF5x.
var (
SPI0 = SPI{Bus: nrf.SPI0}
SPI1 = SPI{Bus: nrf.SPI1}
)
// SPIConfig is used to store config info for SPI.
type SPIConfig struct {
Frequency uint32
SCK uint8
MOSI uint8
MISO uint8
LSBFirst bool
Mode uint8
}
// Configure is intended to setup the SPI interface.
func (spi SPI) Configure(config SPIConfig) {
// Disable bus to configure it
spi.Bus.ENABLE = nrf.SPI_ENABLE_ENABLE_Disabled
// set frequency
var freq uint32
switch config.Frequency {
case 125000:
freq = nrf.SPI_FREQUENCY_FREQUENCY_K125
case 250000:
freq = nrf.SPI_FREQUENCY_FREQUENCY_K250
case 500000:
freq = nrf.SPI_FREQUENCY_FREQUENCY_K500
case 1000000:
freq = nrf.SPI_FREQUENCY_FREQUENCY_M1
case 2000000:
freq = nrf.SPI_FREQUENCY_FREQUENCY_M2
case 4000000:
freq = nrf.SPI_FREQUENCY_FREQUENCY_M4
case 8000000:
freq = nrf.SPI_FREQUENCY_FREQUENCY_M8
default:
freq = nrf.SPI_FREQUENCY_FREQUENCY_K500
}
spi.Bus.FREQUENCY = nrf.RegValue(freq)
var conf uint32
// set bit transfer order
if config.LSBFirst {
conf = (nrf.SPI_CONFIG_ORDER_LsbFirst << nrf.SPI_CONFIG_ORDER_Pos)
}
// set mode
switch config.Mode {
case 0:
conf &^= (nrf.SPI_CONFIG_CPOL_ActiveHigh << nrf.SPI_CONFIG_CPOL_Pos)
conf &^= (nrf.SPI_CONFIG_CPHA_Leading << nrf.SPI_CONFIG_CPHA_Pos)
case 1:
conf &^= (nrf.SPI_CONFIG_CPOL_ActiveHigh << nrf.SPI_CONFIG_CPOL_Pos)
conf |= (nrf.SPI_CONFIG_CPHA_Trailing << nrf.SPI_CONFIG_CPHA_Pos)
case 2:
conf |= (nrf.SPI_CONFIG_CPOL_ActiveLow << nrf.SPI_CONFIG_CPOL_Pos)
conf &^= (nrf.SPI_CONFIG_CPHA_Leading << nrf.SPI_CONFIG_CPHA_Pos)
case 3:
conf |= (nrf.SPI_CONFIG_CPOL_ActiveLow << nrf.SPI_CONFIG_CPOL_Pos)
conf |= (nrf.SPI_CONFIG_CPHA_Trailing << nrf.SPI_CONFIG_CPHA_Pos)
default: // to mode
conf &^= (nrf.SPI_CONFIG_CPOL_ActiveHigh << nrf.SPI_CONFIG_CPOL_Pos)
conf &^= (nrf.SPI_CONFIG_CPHA_Leading << nrf.SPI_CONFIG_CPHA_Pos)
}
spi.Bus.CONFIG = nrf.RegValue(conf)
// set pins
spi.setPins(config.SCK, config.MOSI, config.MISO)
// Re-enable bus now that it is configured.
spi.Bus.ENABLE = nrf.SPI_ENABLE_ENABLE_Enabled
}
// Transfer writes/reads a single byte using the SPI interface.
func (spi SPI) Transfer(w byte) (byte, error) {
spi.Bus.TXD = nrf.RegValue(w)
for spi.Bus.EVENTS_READY == 0 {
}
r := spi.Bus.RXD
spi.Bus.EVENTS_READY = 0
// TODO: handle SPI errors
return byte(r), nil
}