Libraries
Background
lpcSPI9IO.c – write-only 9 bit SPI glue
This module wraps the interface to the LPC SPI routines using some fixed assumptions:
– write only, Master mode
– 12 MHz (SPI peripheral clock = 96 MHz), or otherwise as fast as permitted (1/8 system clock)
– MSB first
– 9-bit data
– clock polarity high, sample on rising edge
– three-wire interface; SSEL is the chip select line/port
This might be generalized later but currently this is intended to be used by other glue routines, not directly from Tollos.
Polling output is used here because the overhead of using interrupts would not give a useful power or speed saving (at 12 MHz each word being written is only 9 clocks, or 750ns).
| Functions | |
|---|---|
| spi9CommandIO | send a one-byte Command |
| spi9Command2IO | send a two-byte Command |
| spi9DataIO | send byte(s) as Data |
| spi9InitIO | initialize SPI and third wire |
| spi9StopIO | stop the SPI device |
spi9CommandIO – send a one-byte Command
int spi9CommandIO(byte b);
b – byte to send
returns 0 if OK, negative if error
spi9Command2IO – send a two-byte Command
int spi9Command2IO(byte b1, byte b2);
b1 – first byte to send
b2 – second byte to send
returns 0 if OK, negative if error
spi9DataIO – send byte(s) as Data
int spi9DataIO(byte *data, uint length);
data – address of data to send
length – count of bytes to send
returns 0 if OK, negative if error
spi9InitIO – initialize SPI and third wire
void spi9InitIO(void);
SSEL is the GPIO line that will be used for the chip select third wire of the 3-wire 9 bit interface; this could be parameterized later to allow multiple devices to be driven on the SPI bus, providing they all use the same protocol.
See the module header for other assumptions.
spi9StopIO – stop the SPI device
void spi9StopIO(void);
This just disables the SPI clock.