spi support

[protos/xbee-avr.git] / spi_servo.c

diff --git a/spi_servo.c b/spi_servo.c
new file mode 100644 (file)
index 0000000..1bb96e7
--- /dev/null
+++ b/spi_servo.c
@@ -0,0 +1,87 @@
+#include <aversive.h>
+#include <aversive/wait.h>
+#include <stdint.h>
+
+#include "spi_servo.h"
+
+#define BYPASS_ENABLE 14
+#define BYPASS_DISABLE 15
+
+/*
+ * SPI protocol:
+ *
+ * A command is stored on 2 bytes. The first one has its msb to 0, and the
+ * second one to 1. The first received byte contains the command number, and the
+ * msb of the servo value. The second byte contains the lsb of the servo value.
+ *
+ * Commands 0 to NB_SERVO are to set the value of servo.
+ * Command 14 is to enable bypass mode.
+ * Command 15 is to disable bypass mode.
+ */
+static volatile union {
+       uint8_t u8;
+       struct {
+               /* inverted: little endian */
+               uint8_t val_msb:3;
+               uint8_t cmd_num:4;
+               uint8_t zero:1;
+       };
+} byte0;
+
+static volatile union {
+       uint8_t u8;
+       struct {
+               /* inverted: little endian */
+               uint8_t val_lsb:7;
+               uint8_t one:1;
+       };
+} byte1;
+
+void spi_servo_init(void)
+{
+       /* real SS ! */
+       DDRK = 0x2;
+       /* SCK, SS & MOSI */
+       DDRB = 0x7;
+
+       /* remove power reduction on spi */
+       PRR0 &= ~(1 << PRSPI);
+
+       /* Enable SPI, Master, set clock rate fck/64 */
+       SPCR = (1<<SPE)|(1<<MSTR)|(1<<SPR1);
+
+       PORTK |= (1<<1);
+
+       spi_servo_set(BYPASS_DISABLE, 0);
+}
+
+void spi_servo_set(uint8_t num, uint16_t val)
+{
+       byte0.val_msb = val >> 7;
+       byte0.cmd_num = num;
+       byte0.zero = 0;
+       byte1.one = 1;
+       byte1.val_lsb = val;
+
+       PORTK &= ~(1<<1);
+       SPDR = byte0.u8;
+       /* Wait for transmission complete */
+       while(!(SPSR & (1<<SPIF)));
+       PORTK |= (1<<1);
+
+       _delay_loop_1(5);
+       PORTK &= ~(1<<1);
+
+       SPDR = byte1.u8;
+       /* Wait for transmission complete */
+       while(!(SPSR & (1<<SPIF)));
+       PORTK |= (1<<1);
+}
+
+void spi_servo_bypass(uint8_t enable)
+{
+       if (enable)
+               spi_servo_set(BYPASS_ENABLE, 0);
+       else
+               spi_servo_set(BYPASS_DISABLE, 0);
+}