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Broke out the SPI read/write into a single routine. Less code repetition -- easier to read and smaller.

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This commit is contained in:
Doug Brown 2011-12-17 13:43:12 -08:00
parent 540e04331a
commit 52d33e077f
1 changed files with 16 additions and 32 deletions
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48
mcp23s17.c
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@ -52,6 +52,7 @@ static bool MCP23S17_Inited = false;
// Private functions
void MCP23S17_WriteBothRegs(uint8_t addrA, uint16_t value);
uint16_t MCP23S17_ReadBothRegs(uint8_t addrA);
uint8_t MCP23S17_ByteRW(uint8_t b);
void MCP23S17_Init()
{
@ -142,6 +143,13 @@ uint16_t MCP23S17_GetPullups(void)
return MCP23S17_ReadBothRegs(MCP23S17_GPPUA);
}
uint8_t MCP23S17_ByteRW(uint8_t b)
{
SPDR = b;
while ((SPSR & (1 << SPIF)) == 0);
return SPDR;
}
void MCP23S17_WriteBothRegs(uint8_t addrA, uint16_t value)
{
// addrA should contain the address of the "A" register.
@ -149,29 +157,17 @@ void MCP23S17_WriteBothRegs(uint8_t addrA, uint16_t value)
ASSERT_CS();
// Just a temporary variable so we read
// the returned byte from the SPI transfer
volatile uint8_t tmp;
// Start off the communication by telling the MCP23S17 that we are writing to a register
SPDR = MCP23S17_CONTROL_WRITE(0);
while ((SPSR & (1 << SPIF)) == 0);
tmp = SPDR;
MCP23S17_ByteRW(MCP23S17_CONTROL_WRITE(0));
// Tell it the first register we're writing to (the "A" register)
SPDR = addrA;
while ((SPSR & (1 << SPIF)) == 0);
tmp = SPDR;
MCP23S17_ByteRW(addrA);
// Write the first byte of the register
SPDR = (uint8_t)((value >> 8) & 0xFF);
while ((SPSR & (1 << SPIF)) == 0);
tmp = SPDR;
MCP23S17_ByteRW((uint8_t)((value >> 8) & 0xFF));
// It should auto-increment to the "B" register, now write that
SPDR = (uint8_t)(value & 0xFF);
while ((SPSR & (1 << SPIF)) == 0);
tmp = SPDR;
MCP23S17_ByteRW((uint8_t)(value & 0xFF));
DEASSERT_CS();
}
@ -182,29 +178,17 @@ uint16_t MCP23S17_ReadBothRegs(uint8_t addrA)
ASSERT_CS();
// Just a temporary variable so we read
// the returned byte from the SPI transfer
volatile uint8_t tmp;
// Start off the communication by telling the MCP23S17 that we are reading from a register
SPDR = MCP23S17_CONTROL_READ(0);
while ((SPSR & (1 << SPIF)) == 0);
tmp = SPDR;
MCP23S17_ByteRW(MCP23S17_CONTROL_READ(0));
// Tell it which register we're reading from (the "A" register)
SPDR = addrA;
while ((SPSR & (1 << SPIF)) == 0);
tmp = SPDR;
MCP23S17_ByteRW(addrA);
// Read the first byte of the register
SPDR = 0;
while ((SPSR & (1 << SPIF)) == 0);
returnVal = (((uint16_t)SPDR) << 8);
returnVal = (((uint16_t)MCP23S17_ByteRW(0)) << 8);
// It should auto-increment to the "B" register, now read that
SPDR = 0;
while ((SPSR & (1 << SPIF)) == 0);
returnVal |= SPDR;
returnVal |= MCP23S17_ByteRW(0);
DEASSERT_CS();