refactor SPI handling and introduce SPI CS, forgotten files

game-ctrl/spi.c

@@ -0,0 +1,50 @@
+#include <msp430g2553.h>
+#include "spi.h"
+
+void spiInit() {
+  // SPI in master mode
+  UCB0CTL0 = UCMST;
+  // SPI timing config
+  UCB0CTL1 = UCSSEL_3;
+  // Faster than 8 ends up in strange communication errors
+  // between the both MCUs.
+  // With 8 the transfer of a complete 110 pixel canvas takes
+  // about 720us.
+  // 8 was still too fast and caused problems.
+  UCB0BR0 = 16; 
+  UCB0BR1 = 0;
+
+  // BIT5: UCB0CLK
+  // BIT6: UCB0SOMI
+  // BIT7: UCB0SIMO
+  P1SEL |= BIT5 | BIT6 | BIT7;
+  P1SEL2 |= BIT5 | BIT6 | BIT7;
+  P1DIR |= BIT5 | BIT7;
+
+  // Device Select Lines: 0: Canvas, 1: Display, 2: Sound
+  P1DIR |= BIT0 | BIT1 | BIT2;
+  // Disable all of them
+  P1OUT |= BIT0 | BIT1 | BIT2;
+
+  // enable SPI module
+  UCB0CTL1 &= ~UCSWRST;
+}
+
+void spiSendBegin(t_SpiDeviceSelector d) {
+  uint16_t bit = ((uint16_t[]){ BIT0, BIT1, BIT2 })[d];
+  P1OUT &= ~bit;
+}
+
+void spiSendEnd(t_SpiDeviceSelector d) {
+  while (UCB0STAT & UCBUSY);
+  uint16_t bit = ((uint16_t[]){ BIT0, BIT1, BIT2 })[d];
+  P1OUT |= bit;
+}
+
+void spiSendOctet(uint8_t v) {
+  // wait for TX buffer empty
+  while (!(UC0IFG & UCB0TXIFG));
+  // load octet into TX buffer
+  UCB0TXBUF = v;
+}
+