Diff: fram/fram.c

Revision:

0:3c04f4b47041

Child:

76:3ef2a46c8b1e

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/fram/fram.c	Thu Jan 11 17:40:08 2018 +0000
@@ -0,0 +1,143 @@
+#include <string.h>
+#include <stdbool.h>
+
+#include "spi.h"
+#include "log.h"
+#include "fram.h"
+
+#define WREN  0x06 // Set Write Enable Latch   0000 0110B
+#define WRDI  0x04 // Reset Write Enable Latch 0000 0100B
+#define RDSR  0x05 // Read Status Register     0000 0101B
+#define WRSR  0x01 // Write Status Register    0000 0001B
+#define READ  0x03 // Read Memory Code         0000 0011B
+#define WRITE 0x02 // Write Memory Code        0000 0010B
+#define RDID  0x9F // Read Device ID           1001 1111B
+
+#define FRAM_ID     0x047f0302
+#define FRAM_MAGIC  42          //Magic number to show that the FRAM has been intialised
+
+bool FramEmpty; //Set in FramInit
+int  FramUsed;  //Initialised in FramInit and used by FramAllocate to remember the next available location
+
+int FramAllocate(int size) //Allocates a number of bytes in FRAM 
+{
+    int start = FramUsed;
+    int used = FramUsed + size;
+    if (used > FRAM_SIZE - 1)
+    {
+        Log("FramAllocate - No more room in FRAM\r\n");
+        return -1;
+    }
+    FramUsed = used;
+    return start;
+}
+int FramInit()
+{
+    //Configure SPI
+    SpiInit();
+    
+    //Check if the FRAM is connected and working properly
+    SpiChipSelect(0);
+    SpiTransfer(RDID);
+    int id = 0;
+    id = (id << 8) + SpiTransfer(0);
+    id = (id << 8) + SpiTransfer(0);
+    id = (id << 8) + SpiTransfer(0);
+    id = (id << 8) + SpiTransfer(0);
+    SpiChipSelect(1);
+    if (id != FRAM_ID)
+    {
+        LogF("FramInit - Expected FRAM id %08x but got %08x\r\n", FRAM_ID, id);
+        return -1;
+    }
+    
+    //Check the first byte to see if the FRAM is initialised and zero if not
+    SpiChipSelect(0);
+    SpiTransfer(READ);
+    SpiTransfer(0);
+    SpiTransfer(0);
+    char magic = SpiTransfer(0);
+    SpiChipSelect(1);
+    FramEmpty = magic != FRAM_MAGIC;
+    if (FramEmpty)
+    {
+        LogF("FramInit - Byte 0 value %d is not the magic value %d so initialising FRAM to zero\r\n", magic, FRAM_MAGIC);
+        SpiChipSelect(0);
+        SpiTransfer(WREN);
+        SpiChipSelect(1); SpiChipSelect(1); SpiChipSelect(1); SpiChipSelect(1); SpiChipSelect(1); SpiChipSelect(1);
+        SpiChipSelect(0);
+        SpiTransfer(WRITE);
+        SpiTransfer(0);
+        SpiTransfer(0);
+        SpiTransfer(FRAM_MAGIC);                           //Set the magic number in byte 0
+        for(int i = 1; i < FRAM_SIZE; i++) SpiTransfer(0); //Zero all other locations
+        SpiChipSelect(1);
+    }
+    FramUsed = 1; //Set the next available location to one past the byte used for the magic number
+    return 0;
+}
+void FramWrite(int address, int len, void* pVoid)
+{
+    if (address + len > FRAM_SIZE - 1 || address < 0)
+    {
+        Log("FramWrite - Invalid FRAM address\r\n");
+        return;
+    }
+    SpiChipSelect(0);
+    SpiTransfer(WREN);
+    SpiChipSelect(1); SpiChipSelect(1); SpiChipSelect(1); SpiChipSelect(1); SpiChipSelect(1); SpiChipSelect(1); //Deselect must be at least 60ns. One operation at 96MHz is about 10ns
+    SpiChipSelect(0);
+    SpiTransfer(WRITE);
+    SpiTransfer(address >> 8);
+    SpiTransfer(address & 0xFF);
+    char* p = (char*)pVoid;
+    for (int i = 0; i < len; i++) SpiTransfer(*p++);
+    SpiChipSelect(1);
+}
+void FramRead(int address, int len, void* pVoid)
+{
+    if (address + len > FRAM_SIZE - 1 || address < 0)
+    {
+        Log("FramRead - Invalid FRAM address\r\n");
+        return;
+    }
+    SpiChipSelect(0);
+    SpiTransfer(READ);
+    SpiTransfer(address >> 8);
+    SpiTransfer(address & 0xFF);
+    char* p = (char*)pVoid;
+    for (int i = 0; i < len; i++) *p++ = SpiTransfer(0);
+    SpiChipSelect(1);
+}
+
+int FramLoad(int len, void* pValue, void* pDefault)
+{
+    int address = FramAllocate(len);
+    if (address >= 0) 
+    {
+        if (FramEmpty)
+        {
+            if (pDefault)
+            {
+                int defaultHasContent = 0;
+                char* pFrom = (char*)pDefault;
+                char* pTo   = (char*)pValue;
+                for (int i = 0; i < len; i++);
+                {
+                    if (*pFrom) defaultHasContent = 1;
+                    *pTo++ = *pFrom++;
+                }
+                if (defaultHasContent) FramWrite(address, len, pValue);
+            }
+            else //pDefault is NULL so zero the setting
+            {
+                memset(pValue, 0, len);
+            }
+        }
+        else
+        {
+            FramRead(address, len, pValue);
+        }
+    }
+    return address;
+}