OctoClock support

1 files changed, 844 insertions, 0 deletions

diff --git a/firmware/octoclock/OctoClock.c b/firmware/octoclock/OctoClock.c
new file mode 100644
index 000000000..07397601d
--- /dev/null
+++ b/firmware/octoclock/OctoClock.c
@@ -0,0 +1,844 @@
+/*
+ * OctoClock.c
+ *
+ * V1.00 -- May 2013
+ *
+ *
+ * V1.03 -- Correct the switch to be UP for Internal and DOWN for External
+ *          This means that the bat handle "points at" (sort of) the lower-left LED, which
+ *          is the "STATUS" LED, which gets lit up when the external 10 MHz is present
+ *          The "10 MHz Signal Detect" code accepts a very wide range of "10 MHz" signals
+ *          23 April 2013
+ *
+ *
+ * V1.02 -- Make LEDs consistent with Chassis - Top LED is INTERNAL; middle is EXTERNAL; bottom is STATUS
+ *
+ * STATUS is ON if the 10 MHz external input is present.   19 April 2013
+ *
+ *
+ * V1.01: Modify TI chip initialization to be in differentail mode
+ * which allows 10 MHz input down to 0.1 Volts according to the datasheet.
+ *
+ *
+ * New Version that supports CLOCK board Version 1.0
+ *
+ * Author: Michael@Cheponis.Com with code borrowed liberally from
+ * previous AVR projects
+ *
+ */
+
+/*
+ * Copyright 2013 Ettus Research LLC
+ */
+
+
+
+
+
+
+/* CLKSEL0 = 1   SUT1..0 is 11   CKOPT = 0   CKSEL3..1 is 111  => big output swing, long time to start up */
+/*
+
+NOT in M103 compatibility mode,  no WDT, CKOPT full rail-to-rail  xtal osc, 16K CK (16K clock cycles),
+additional delay 65ms for Crystal Oscillator, slowly rising power
+
+Very conservative settings; if lower power osc required, change CKOPT to '1'  (UNPROGRAMMED)  or, if you will,
+CKOPT = [ ]
+
+
+
+M103C = [ ]
+WDTON = [ ]
+OCDEN = [ ]
+JTAGEN = [X]
+SPIEN = [X]
+EESAVE = [ ]
+BOOTSZ = 4096W_F000
+BOOTRST = [ ]
+CKOPT = [X]
+BODLEVEL = 2V7
+BODEN = [ ]
+SUT_CKSEL = EXTHIFXTALRES_16KCK_64MS
+
+EXTENDED = 0xFF (valid)
+HIGH = 0x89 (valid)
+LOW = 0xFF (valid)
+
+
+*/
+
+// No interrupts are required
+
+#include "OctoClock-io.h"
+
+#include <avr/io.h>
+#include <avr/interrupt.h>
+
+
+#ifdef On
+#undef On
+#endif
+
+#ifdef Off
+#undef OFf
+#endif
+
+#define Off	(0)
+#define On (!Off)
+
+
+// Important for the Serial Port, not used at the moment
+#define	FOSC	(7372800)
+#define BAUD	(115200)
+
+#define MYUBRR FOSC/16/BAUD-1
+
+
+#define wait() for(u16 u=14000; u; u--) asm("nop");
+
+
+
+enum LEDs {Top,Middle,Bottom}; // Top is 0, Mid is 1, and Bottom is 2
+
+void
+led(enum LEDs which, int turn_it_on){
+	
+	u8 LED = 0x20 << which; // selects the proper bit
+	
+	if(turn_it_on)
+		PORTC |= LED;
+	else
+		PORTC &= ~LED;
+	
+}
+
+
+enum TI_Input_10_MHz {Primary_GPS, Secondary_Ext};
+
+void setup_TI_CDCE18005(enum TI_Input_10_MHz);
+
+
+
+
+/*****************************************************************************************
+
+			SPI routines
+
+******************************************************************************************/
+
+
+
+/* All macros evaluate to compile-time constants */
+ 
+/* *** helper macros * * */
+ 
+/* turn a numeric literal into a hex constant
+ (avoids problems with leading zeros)
+ 8-bit constants max value 0x11111111, always fits in unsigned long
+ */
+ #define HEX__(n) 0x##n##LU
+ 
+/* 8-bit conversion function */
+ #define B8__(x) ((x&0x0000000FLU)?1:0) \
+ +((x&0x000000F0LU)?2:0) \
+ +((x&0x00000F00LU)?4:0) \
+ +((x&0x0000F000LU)?8:0) \
+ +((x&0x000F0000LU)?16:0) \
+ +((x&0x00F00000LU)?32:0) \
+ +((x&0x0F000000LU)?64:0) \
+ +((x&0xF0000000LU)?128:0)
+
+// Damn, that is SERIOUS magic ... ;-)  Yes, I know how it works
+// but it's pretty cool....
+
+ 
+/* *** user macros *** */
+ 
+/* for upto 8-bit binary constants */
+ #define Bits_8(d) ((unsigned char)B8__(HEX__(d)))
+ 
+/* for upto 16-bit binary constants, MSB first */
+ #define Bits_16(dmsb,dlsb) (((unsigned short)Bits_8(dmsb)<<8) \
+ + Bits_8(dlsb))
+ 
+/* for upto 32-bit binary constants, MSB first */
+ #define Bits_32(dmsb,db2,db3,dlsb) (((unsigned long)Bits_8(dmsb)<<24) \
+ + ((unsigned long)Bits_8(db2)<<16) \
+ + ((unsigned long)Bits_8(db3)<<8) \
+ + Bits_8(dlsb))
+ 
+/* Sample usage:
+ Bits_8(01010101) = 85
+ Bits_16(10101010,01010101) = 43605
+ Bits_32(10000000,11111111,10101010,01010101) = 2164238933
+ */
+ 
+
+
+enum CDCE18005 {Reg0, Reg1, Reg2, Reg3, Reg4, Reg5, Reg6, Reg7, Reg8_Status_Control,
+	  Read_Command=0xE, RAM_EEPROM_Unlock=0x1F, RAM_EEPROM_Lock=0x3f} 
+	  TI_CDCE18005;
+
+// Table of 32-bit constants to be written to the TI chip's registers.
+
+// Damn, inconsistent data sheet!  Special settigns see p35 of TI datasheet
+
+// For the GPS's 10 MHz output
+u32 table_Pri_Ref[] = {
+
+	Bits_32(1,01010100,0,0),	// Reg 0
+	Bits_32(1,01010100,0,0),	// Outputs LVCMOS Positive&Negative Active - Non-inverted
+	Bits_32(1,01010100,0,0),
+	Bits_32(1,01010100,0,0),
+	Bits_32(1,01010100,0,0),	// All have output divide ratio to be 1; Aux Output is OFF
+	
+	Bits_32(0,0,1001,11010100),  // Reg 5  LVCMOS in; p31 of TI datasheet
+	
+	Bits_32(1,0,0010000,0),		// Reg 6	// SCAS863A – NOVEMBER 2008 – REVISED JUNE 2011
+	
+	Bits_32(1,01000000,0,0),	// Reg 7
+	//        76543210
+	Bits_32(0,0,1,10000000) // Reg8  Status/Control
+};
+
+
+// Looks like it's doing the correct thing re: SPI interface
+// This is *definitely* AC coupled.  I removed those resistors to +3.3 and ground
+// signal looked no different with differential measurement.  Added 240+470 to 
+// center tap of secondary side to bias up to approx 1.2V for proper LVDS
+//
+// For the External 10 MHz input   LVDS with external termination  -- Effectively DC coupled
+
+u32 table_Sec_Ref[] = {
+	Bits_32(0001,01010100,0,100000),// Reg 0 -- use Secondary Reference for all channels
+	Bits_32(0001,01010100,0,100000),// Outputs LVCMOS Positive&Negative Active - Non-inverted
+	Bits_32(0001,01010100,0,100000),
+	Bits_32(0001,01010100,0,100000),
+	Bits_32(0001,01010100,0,100000),
+	
+//	Bits_32(0,0,00001000,10010111),  // Reg 5  LVDS with External Termination p32 of TI datasheet
+//	Bits_32(0,0,00001000,11010111),  // Reg 5  LVDS with INTERNAL Termination p32 of TI datasheet
+
+// May 2013 -- Turn OFF the LVDS Safe Mode, as it supposedly causes input thresholds to be increased.
+
+//     	Bits_32(0,0,1001,10011011),  // Reg 5, try again.  Pretty soon, try new board...
+
+      	Bits_32(0,0,1,10011011),  // Reg 5, Failsafe OFF   b5.11 = 0
+		  
+
+//       	Bits_32(0,0,1001,11011011),  // Reg 5, try again.  Pretty soon, try new board...
+	// Try with DC input termination;  bit 6 is a "1"  2013 March
+	// Seems to not work correctly.
+
+	
+//	Bits_32(1,0,0000000,0),  // Reg 6; note that 6.12 must be 1 for LVDS w/External Termination, 0 int
+//	Bits_32(1,0,0000000,0),  // Reg 6; try Internal and DC coupling
+	Bits_32(1,0,10000,0),  // Reg 6; try again
+	
+	Bits_32(1,01000000,0,0),
+	Bits_32(0,0,1,10000000) // Reg8  Status/Control
+};
+
+//; Table 19 conflicts with Tables 5 thru 9 - in how LVCMOS outputs are defined
+// extra error in Table 9, for bits 24 and 25
+//
+// Could combine these into just table[][] with 1st subscript being 0 or 1 for Primary or Secondary
+// Maybe want to to that.
+
+int table_size = sizeof (table_Pri_Ref) / sizeof(u32);
+//int table_size = 1; // Testing read and write of Register 0 -- don't want excess SPI transactions
+//NOTE!!! Still need to shift left by 4 and OR in register, as defined in TI_CDCE18005 enum, above.
+
+
+enum Levels {Lo, Hi};
+	
+#define CLK	(PA0) // Shift by 0 bits  (PA.0)
+#define CE_	(PA1) // Is really the "Chip Disable" signal, as Hi disables SPI
+#define MOSI	(PA2)
+#define MISO	(PA3)
+#define PD_	(PA4)
+#define SYNC_	(PA5)
+
+void
+set_bit(u8  bit_number, enum Levels bit_value){
+
+ if(bit_value == Hi)
+	PORTA |= 1<<bit_number;
+ else
+	PORTA &= ~ (1<<bit_number);
+}
+
+
+bool
+get_bit(u8  bit_number){
+	asm("nop");
+	
+	u8 portA = PINA;	// Maybe something is strange they way PORTA is read?
+//	USART_Transmit( hex_table [0xf & (portA >> 4)], Control );
+//	USART_Transmit( hex_table [0xf & portA], Control );
+//	USART_Transmit(CR, Control); USART_Transmit(LF,Control);
+	
+	return (portA &  1<< bit_number) > 0 ? TRUE : FALSE;
+	//return (portA & 8) != 0; // It's always MISO, so nail it for the moment
+}
+
+
+void
+send_SPI(u32 bits){
+// Send 32 bits to TI chip, LSB first.
+// Don't worry about reading any bits back at this
+// time, although for production, may want to do that
+// as an error-check / integrity check.
+
+/*
+#define CLK		(PA0) // Shift by 0 bits  (PA.0)
+#define CE_		(PA1) // Is really the "Chip Disable" signal, as Hi disables SPI
+#define MOSI	(PA2)
+#define MISO	(PA3)
+#define PD_		(PA4)
+#define SYNC_	(PA5)
+*/
+
+//Basically, when the clock is low, one can set MOSI to anything, as it's ignored.
+
+ set_bit(CE_, Lo);	// Start SPI transaction with TI chip
+ 
+ for (u8 i=0; i<32; i++){  // Foreach bit we need to send
+	set_bit(MOSI, ((bits & (1UL<<i)) ? Hi : Lo) );   // LSB first
+	asm("nop"); // Need a little more delay before L->H on clock; (REALLY?)
+	set_bit(CLK, Hi);
+	set_bit(CLK, Lo);  // Pulse the clock to clock in the bit
+ }
+// 	USART_Transmit(CR, Control); USART_Transmit(LF,Control);
+ //set_bit(MOSI, Lo); // Not needed, but keeps all bits zeros except /CE when idle
+ set_bit(CE_, Hi);  // OK, transaction is over
+//	USART_Transmit(CR, Control); USART_Transmit(LF,Control);
+}
+
+// Takes about 7.6 ms to init all regs (as seen on scope)
+// There is a very interesting phenomenon that is occurring --- The bit-to-bit time 
+// at the beginning of transmission is 15 usec.  However, as the number of bits
+// shifted to the left increases (as i increases in the for() loop )
+// the time between bits elongates.  It's about 37 usec between bits 
+// 30 and 31 (the last 2 bits).  It's kinda cool, because it's easy to
+// know when the new word begins because the clock pulses will be
+// closer together.  
+
+// See if it checks: (15+37)/2 = 26 usec between average bits
+// 32 bits * 9 words * 26 usec = 7.49 ms --- but have to add
+// in the little bit of time that CE_ goes high; so 7.6 ms
+// is a very reasonable number.  (Assumes linear increase in
+// time as the number of shifts goes up, which seems to
+// work OK here.)
+//
+// Of course, using a table instead of doing those shifts all the
+// time would fix this; but it (should not) doesn't matter for this
+// SPI interface.
+//
+// So far, the first word looks good, and the beginning of writing
+// Register 1 also looks good.
+//
+
+
+
+
+
+
+// enum TI_Input_10_MHz {Primary_GPS, Secondary_Ext};
+
+void
+reset_TI_CDCE18005(){
+// First, reset the chip.  Or, if you will, pull /SYNC low then high
+set_bit(CE_, Hi);
+set_bit(PD_, Lo);
+wait(); // This should put the EEPROM bits into the RAM -- we don't care, but should init the chip
+
+set_bit(PD_, Hi); // Out of Power Down state
+wait();
+
+set_bit(SYNC_, Lo);
+wait();
+set_bit(SYNC_, Hi);
+
+wait();
+// Now, by gosh, that darn chip ought to be fully enabled!
+}
+	
+void
+setup_TI_CDCE18005(enum TI_Input_10_MHz which_input){
+ // Send the table of data to init the clock distribution chip.  Uses SPI.
+ u32 temp;
+ 
+ //reset_TI_CDCE18005();   // This REALLY should not be necessary
+ 
+ if(which_input == Primary_GPS){
+	 
+	 for(u8 i=0; i<table_size; i++){
+		 temp = table_Pri_Ref[i]<<4;
+		 temp |= i;
+		// print_u32(temp); // Debug *mac* -- correct
+		 send_SPI(temp); // Make sure the register's address is in the LSBs
+	 }	
+ }	
+ else { // is Secondary_Ext -- External 10 MHz input from SMA connector
+		
+		 for(u8 i=0; i<table_size; i++){
+			 temp = table_Sec_Ref[i]<<4;
+			 temp |= i;
+			 send_SPI(temp); // Make sure the register's address is in the LSBs
+		 }
+ }
+}		 
+u32 
+receive_SPI(){
+ u32 bits;
+	
+ bits = 0;
+ 
+ set_bit(CE_, Hi); // Make sure we're inactive
+ set_bit(CLK, Lo); // and clk line is inactive, too
+ set_bit(MOSI,Lo); // Make our bit output zero, for good measure
+ 
+
+ set_bit(CE_, Lo);	// Start SPI transaction with TI chip; MOSI is don't care
+
+	for (u8 i=0; i<32; i++){  // Foreach bit we need to get
+		bits >>= 1; // get ready for next bit - NOTE: Only do this if we REALLY are putting in another bit
+		set_bit(CLK, Hi);	// CPU is so slow, it easily meets setup & hold times
+		//                            76543210
+		if( get_bit(MISO) ) bits |= 0x80000000; // because we receive the LSB first
+		set_bit(CLK, Lo);  // Pulse the clock to clock in the bit
+	}
+ set_bit(CE_, Hi);  // OK, transaction is over
+
+ return (u32)(bits >> 4); // Ditch the lower 4 bits, which only contain the address
+}
+
+u32
+get_TI_CDCE18005(enum CDCE18005 which_register){
+	u32 get_reg_value;
+	
+	get_reg_value = 0;
+	get_reg_value = (0xf0 & which_register << 4) | Read_Command;
+	send_SPI(get_reg_value); // This tells the TI chip to send us the reg. value requested
+	return receive_SPI();
+};
+
+
+bool
+check_TI_CDCE18005(enum TI_Input_10_MHz which_input, enum CDCE18005 which_register)	{
+  //		USART_Transmit(CR, Control); USART_Transmit(LF,Control); //reset_TI_CDCE18005();
+	if(which_input == Primary_GPS){
+		u32 read_value = get_TI_CDCE18005(which_register);
+		return read_value == table_Pri_Ref[which_register];	
+	}
+	else {
+		u32 read_value = get_TI_CDCE18005(which_register);
+		return read_value == table_Sec_Ref[which_register];
+	}
+};
+// This could obviously be done more elegantly to share more code; but this is
+// simple and easy to understand	
+
+
+
+
+
+
+
+
+void
+Setup_Atmel_IO_Ports(){
+	
+	
+/////////////////////////////////////////////////////////////////////////////					
+/*
+ * PORT A
+ * 
+ *pin# Sig	Our Functional Name
+ *
+ * p51 PA0	CLK_CDCE	to U205 pin 24 --   L-->H edge latches MOSI and MISO in CDCE18005
+ * p50 PA1	CE_CDCE		Low = Chip Enabled for SPI comm  to U205 pin 25
+ * p49 PA2	MOSI_CDCE	Goes to CDCE18005 - U205 pin 23
+ * p48 PA3	MISO_CDCE	Input	Comes from U205 pin 22
+ * p47 PA4	PD_CDCE		Low = Chip is in Power-Down state; is Hi for normal operation U205 pin 12
+ * p46 PA5	SYNC_CDCE	Low = Chip is sync'd with interal dividers; Hi for normal operation U205 pin 14
+ * p45 PA6	PPS_SEL		Low --> PPS_EXT selected; Hi -> PPS_GPS selected;    to U203 pin 1
+ * p44 PA7	gps_lock	Input	Comes from M9107 - U206 pin 3
+ *
+ */
+
+// Bit #:  76543210
+PORTA = Bits_8(00110010); // /pd_cdcd, /sync_code, /ce need to be 1 (disabled) to start
+DDRA =   1<<DDA6 | 1<<DDA5 | 1<<DDA4 | 1<<DDA2 | 1<<DDA1 | 1<<DDA0; //// all bits are outputs, except PA7 (gps_lock) and PA3 (MISO_CDCE) are inputs
+
+
+					
+/////////////////////////////////////////////////////////////////////////////					
+/*
+ * Port B
+ *
+ *pin# Sig	Our Functional Name
+ *
+ * p10 PB0	Ethernet /SEN
+ * p11 PB1	Ethernet SCLK
+ * p12 PB2	Ethernet MOSI
+ * p13 PB3	Ethernet MISO
+ * p14 PB4	Not connected, set as output with value 0
+ * p15 PB5	Ethernet /RESET  -- Set to HI for normal use, weak input
+ * p16 PB6	Ethernet /WOL  --- Wake on LAN -- set, weak input
+ * p17 PB7	Not connected, set as output with value 0
+ *
+ */
+ 
+
+ PORTB = Bits_8(01100001);		// Initial Value is all zeros
+ DDRB = 1<<DDB2 | 1<<DDB4 | 1<<DDB7;  // MOSI is an output; the Not Connected pins are also outputs
+
+
+					
+/////////////////////////////////////////////////////////////////////////////					
+/*
+ * Port C
+ *
+ *pin# Sig	Our Functional Name
+ *
+ * p34 PC0	Not connected, set as output with value 0
+ * p35 PC1	Reference Select Switch INPUT
+ * p36 PC2	Not connected, set as output with value 0
+ * p37 PC3	Not connected, set as output with value 0
+ * p38 PC4	Not connected, set as output with value 0
+ * p40 PC5	"Top LED" of D103 3-stack of green LEDs
+ * p41 PC6	"Middle LED"
+ * p43 PC7	"Bottom LED"
+ *
+ */
+PORTC = 0;		// Initial Value is all zeros
+DDRC =  ~( 1<<DDC1 ); 	// All bits are outputs, except PC1. including the 5 Not Connected bits
+
+ 
+
+/////////////////////////////////////////////////////////////////////////////					
+/*
+ * Port D
+ *
+ *pin# Sig	Our Functional Name
+ *
+ * p25 PD0	Ethernet /INT input
+ * p26 PD1	GPS NMEA bit, output
+ * p27 PD2	GPS Serial Out  (RXD; INT1)  INPUT
+ * p28 PD3	GPS Serial In   (TXD)        OUTPUT
+ * p29 PD4	GPS Present, INPUT  hi = Present
+ * p30 PD5	Not connected, set as output with value 0
+ * p31 PD6	Not connected, set as output with value 0
+ * p32 PD7	Not connected, set as output with value 0
+ *
+ */
+PORTD = 0;		// Initial Value is all zeros
+DDRD =  1<<DDD1 | 1<<DDD3;
+
+					
+
+/////////////////////////////////////////////////////////////////////////////					
+/*
+ * Port E
+ *
+ *pin# Sig Dir	Our Functional Name
+ *
+ * p2 PE0 In	avr_rxd	(Also MOSI [PDI] when used for SPI programming of the chip)
+ * p3 PE1 Out	avr_txd (Also MISO [PDO] when used for SPI programming of the chip)
+ * p4 PE2 In	avr_cts
+ * p5 PE3 Out	avr_rts  DUE TO MOD, make this an input, too (as we go direct GPSDO to FPGA via level translators)
+ * p6 PE4 In	PPS_GPS
+ * p7 PE5 In	PPS_EXT_n
+ * p8 PE6 In	Not Connected
+ * p9 PE7 In	Not Connected
+ *
+ */
+PORTE = 0;
+DDRE =  1<<DDE1; // make outputs, set to zero.  PE1 is usart0 TXD
+
+
+/////////////////////////////////////////////////////////////////////////////					
+/*
+ * Port F
+ *
+ * Split into 2 nibbles; goes to Amp/Filter board to select ENABLE and two bits to select band
+ * one bit per nibble is not connected.
+ *
+ * pin Sig Dir		Our Functional Name
+ * num
+ *
+ * p61 PF0 Out		J117 pin 3  (J117 pins 1 and 2 are GND)
+ * p60 PF1 Out		J117 pin 4
+ * p59 PF2 Out		J117 pin 5
+ * p58 PF3 Out		J117 pin 6
+ * p57 PF4 Out		J118 pin 3  (J118 pins 1 and 2 are GND)
+ * p56 PF5 Out		J118 pin 4
+ * p55 PF6 Out		J118 pin 5
+ * p54 PF7 Out		J118 pin 6
+ *
+ */
+ 
+
+PORTF = 0;		// Initial Value is all zeros; be sure ENABLE bits are active high!!!!
+DDRF =  0xff;	// All bits are outputs
+
+
+
+	
+led(Middle,On);
+setup_TI_CDCE18005(Primary_GPS);	// 10 MHz from Internal Source
+
+led(Top,On); 
+PORTA |= (1<<PA6);	// PPS from Internal source
+
+
+}
+
+/////////////////////////////////////////////////////////////////////////////
+
+//enum TI_Input_10_MHz {Primary_GPS, Secondary_Ext};
+
+//setup_TI_CDCE18005(enum TI_Input_10_MHz);
+
+bool  Global_GPS_Present = (bool)FALSE;
+bool Global_Ext_Ref_Is_Present = (bool)FALSE; // NOT PRESENT unless proven so...
+// This was initially global becasue it was to be set in an interrupt routine
+// But it turned out interrupts were not needed.  But kept this in because
+// although it's a Global, it is the only one, and it makes it easier to
+// go back and use interrupts if absolutely necessary.  It could be
+// removed and replaced with some local variable that gets passed
+// around, but, really, it seems OK to me like this.
+
+
+
+void
+LEDs_Off(){
+ led(Top,Off);
+ led(Middle,Off);
+ led(Bottom,Off);
+}
+
+
+void
+Force_Internal(){
+  // led(Middle,On);
+ led(Top,On);
+ led(Middle,Off);
+ led(Bottom,On);
+
+ setup_TI_CDCE18005(Primary_GPS);
+
+ // Set PPS to Primary (1) n.b.:  "1" in general means "Internal" for all such signals
+ PORTA |= (1<<PA6);	// PPS from Internal source
+}
+
+
+void
+Force_External(){
+  // led(Middle, Off);
+  led(Top, Off);
+  led(Middle, On);
+  led(Bottom, On);
+
+ setup_TI_CDCE18005(Secondary_Ext);
+
+ // Set PPS to External (0
+ PORTA &= ~(1<<PA6);	// PPS from External source
+}
+
+
+/////////////////////////////////////////////////////////////////////////////
+
+void
+Prefer_Internal(){
+
+  if(Global_GPS_Present)
+    Force_Internal();
+  else if(Global_Ext_Ref_Is_Present)
+    Force_External();
+  else
+    LEDs_Off();
+}
+
+
+
+
+
+void
+Prefer_External(){   // IF EXTERNAL IS OK, then do this stuff
+  // if external is NOT OK, then force Internal
+  if(Global_Ext_Ref_Is_Present)
+    Force_External();
+  else if(Global_GPS_Present)
+    Force_Internal();
+  else
+    LEDs_Off();
+}
+ 
+
+
+// Turns out, we don't need interrupts
+
+
+#if 0
+//;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+//;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+//;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+u8 Global_Tick_Counter = (u8)0;
+u8 Global_Ext_Ref_Detect_Counter = (u8)0;
+
+// External Reference Detect interrupt; nominally at 610 Hz (10 MHz / 2**14 )
+ISR ( _VECTOR(1)){
+  asm("cli");	// Global Interrupt Disable --- enable with SEI if desired later
+
+
+  Global_Ext_Ref_Detect_Counter++ ;  // We reset this elsewhere
+
+  asm("sei");	// Global Interrupt Enable
+}
+
+
+// Timer 0 Overflow Handler
+ISR ( _VECTOR(16)){
+  static u8 led_state = Off;
+
+  asm("cli");	// Global Interrupt Disable --- enable with SEI if desired later
+
+  led_state = (led_state ? Off : On);
+
+  asm("sei");	// Global Interrupt Enable
+}
+
+//;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+//;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+//;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+
+
+void
+Setup_Atmel_Interrupts(){
+  // Timer 0 is all we need -- but simplest if both Timer 0 AND IRQ1 (ext_ref_detect 610 Hz signal) also
+  // Nah, don't need this...
+}
+
+#endif
+
+
+
+bool
+Check_What_Is_Present(){
+
+  Global_GPS_Present = (PIND & (1<<DDD4)) != 0; // See if +5 scaled to 3.3 from GPSDO is there
+
+
+  volatile u8 portE = PINE;
+  volatile u8 prev, now;
+
+  prev = ( portE & (1 << DDE7) ?  1 : 0); // Get PREVIOUS state of the input
+  for(u16 c=1; c; c++){
+    portE = PINE;
+    now = ( portE & (1 << DDE7) ?  1 : 0);
+    if(prev != now){
+      Global_Ext_Ref_Is_Present = (bool)TRUE;
+      return (bool)TRUE;
+    }
+  }
+  // Else, if it didn't wiggle in that time, then it didn't wiggle
+  // So ext. is NOT present
+
+  Global_Ext_Ref_Is_Present = (bool)FALSE;
+  return (bool)FALSE;
+
+}
+
+
+bool
+get_Switch_State(){
+ u8  portC = PINC;
+
+ // return (bool)(portC &  (1<<DDC1) ? On : Off); 
+ return (bool)(portC &  (1<<DDC1) ? Off : On);  // UP is prefer internal,
+                                                // DOWN is prefer external
+}
+
+
+/////////////////////////////////////////////////////////////////////////////
+/////////////////////////////////////////////////////////////////////////////
+//                            M A I N                                      //
+/////////////////////////////////////////////////////////////////////////////
+/////////////////////////////////////////////////////////////////////////////
+
+	
+int 
+main(void){
+
+  bool Old_Switch_State, Current_Switch_State, Old_Global_Ext_Ref_Is_Present = FALSE;
+
+
+
+ asm("cli");	// Global Interrupt Disable --- enable with SEI if desired later
+
+ Setup_Atmel_IO_Ports();
+
+ // Setup_Atmel_Interrupts();
+
+
+ /*
+  * DO THIS FOREVER:
+  *  
+  *  
+  * get_switch_state
+  *  
+  * if SWITCH_CHANGED:
+  *  
+  *  
+  *   if PREFER_INTERNAL:
+  *     if INTERNAL_PRESENT do_internal
+  *     else if EXTERNAL_PRESENT do_external
+  *     else LEDs OFF
+  *
+  *   if PREFER_EXTERNAL:
+  *     if EXTERNAL_PRESENT do_external
+  *     else if INTERNAL_PRESENT do_internal
+  *     else LEDs OFF
+  *
+  */
+
+
+
+
+ Old_Switch_State = ! get_Switch_State();
+
+ // Because down below, we use this to get state swap...
+ // So we arbitrarily set the PREVIOUS state to be the "other" state
+ // so that, below, we trigger what happens when the switch changes
+ // This first "change" is therefore artificial to keep the logic, below, cleaner
+  
+ while(TRUE) {
+   Check_What_Is_Present(); // Set "Global_Ext_Ref_Is_Present" and "Global_GPS_Present"
+
+   // Off means "Prefer External" -- DOWN
+   // On  means "Prefer Internal" -- UP
+
+   Current_Switch_State = get_Switch_State();
+  
+   if( (Current_Switch_State != Old_Switch_State)  || 
+       (Global_Ext_Ref_Is_Present != Old_Global_Ext_Ref_Is_Present) ) {
+
+     Old_Switch_State = Current_Switch_State;
+     Old_Global_Ext_Ref_Is_Present = Global_Ext_Ref_Is_Present;
+
+     if(Current_Switch_State == On)
+       Prefer_Internal();
+     else
+       Prefer_External();
+   } // if()  checking for different switch status
+
+
+ } // WHILE() loop
+
+
+} /*end  "main" of  Program 'OctoClock.c */