Diff: main/spi.c

Revision:

0:3c04f4b47041

Child:

1:ccc66fdf858d

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main/spi.c	Thu Jan 11 17:40:08 2018 +0000
@@ -0,0 +1,57 @@
+#include "peripherals.h"
+#include "log.h"
+
+#define CS_BIT_MASK_0 1 << 6 //pin 0.6
+
+void SpiInit(void)
+{
+    //Enable power
+    LPC_SC->PCONP |= 0x0400; //Table 46 Bit 10 is SSP1
+    
+    //Configure
+    LPC_SSP1->CR0 |= 7 << 0; //3:0 8 bit transfer
+    LPC_SSP1->CR0 |= 0 << 4; //5:4 SPI
+    LPC_SSP1->CR0 |= 0 << 6; //7:6 Mode 0
+    LPC_SSP1->CR0 |= 0 << 8; //divide by 1
+
+    //Set prescaler bps = PCLK / PS ==> PS = PCLK / bps ==> PS = 96/16 = 6
+    LPC_SSP1->CPSR = 6; //Bit 0 must be 0. 6 ==> 16 bps which is within the 20MHz allowed by the FRAM
+    
+    //Select the function of the ssel pin: P0.6
+    LPC_PINCON->PINSEL0  &= ~0x3000;
+    LPC_PINCON->PINSEL0  |=  0x0000; // table 80. 13:12 = 0b00 ==> GPIO
+    LPC_PINCON->PINMODE0 &= ~0x3000; // table 88. 13:12 = 0b00 ==> enable pull-up resistor
+    LPC_GPIO0->FIODIR |= CS_BIT_MASK_0; //Set the direction to 1 == output
+    LPC_GPIO0->FIOSET  = CS_BIT_MASK_0; //Deselect the output == CS = 1
+    
+    //Select the function of the sck, miso and mosi pins: P0.7, P0.8 and P0.9
+    LPC_PINCON->PINSEL0  &= ~0xFC000;
+    LPC_PINCON->PINSEL0  |=  0xA8000; // table 80. 15:14, 17:16, 19:18 = 0b10
+    LPC_PINCON->PINMODE0 &= ~0xFC000; // table 88. = 0b00 ==> enable pull-up resistor
+    
+    //Enable operation
+    LPC_SSP1->CR1 |= 2; //Enable the SSP controller
+}
+void SpiChipSelect(int value)
+{
+    if (value) LPC_GPIO0->FIOSET = CS_BIT_MASK_0;
+    else       LPC_GPIO0->FIOCLR = CS_BIT_MASK_0;
+}
+void SpiWrite(char byte)
+{
+    LPC_SSP1->DR = byte; //This loads the next frame in the TX FIFO
+}
+int  SpiBusy(void)
+{
+    return LPC_SSP1->SR & 0x10; //bit 4 is BSY. This bit is 0 if the SSPn controller is idle, or 1 if it is currently sending/receiving a frame and/or the Tx FIFO is not empty.
+}
+char SpiRead(void)
+{
+    return LPC_SSP1->DR & 0xFF; //This reads the oldest frame in the RX FIFO
+}
+char SpiTransfer(char byte)
+{
+    SpiWrite(byte);
+    while(SpiBusy()) /*spin until not busy, at 16 bits per us or 2 bytes per us should be only 48 operations*/;
+    return SpiRead();
+}