one more example for blinker is added, some comments to the bootloade…

blinker01_alternative/Makefile

@@ -0,0 +1,32 @@
+
+ARMGNU ?= arm-none-eabi
+#ARMGNU ?= arm-linux-gnueabi
+
+AOPS = --warn --fatal-warnings
+COPS = -Wall -Werror -O2 -nostdlib -nostartfiles -ffreestanding
+
+all : kernel.img
+
+clean :
+	rm -f *.o
+	rm -f *.bin
+	rm -f *.hex
+	rm -f *.srec
+	rm -f *.elf
+	rm -f *.list
+	rm -f *.img
+
+vectors.o : vectors.s
+	$(ARMGNU)-as $(AOPS) vectors.s -o vectors.o
+
+notmain.o : notmain.c
+	$(ARMGNU)-gcc $(COPS) -c notmain.c -o notmain.o
+
+notmain.elf : memmap vectors.o notmain.o
+	$(ARMGNU)-ld vectors.o notmain.o -T memmap -o notmain.elf
+	$(ARMGNU)-objdump -D notmain.elf > notmain.list
+
+kernel.img : notmain.elf
+	$(ARMGNU)-objcopy --srec-forceS3 notmain.elf -O srec notmain.srec
+	$(ARMGNU)-objcopy notmain.elf -O binary kernel.img
+

blinker01_alternative/README

@@ -0,0 +1,9 @@
+
+See the top level README for information on where to find documentation
+for the raspberry pi and the ARM processor inside.  Also find information
+on how to load and run these programs.
+
+This is an LED blinker example for the pi zero.
+
+Blinking with LED connected to GPIO 16 as alternative to blinker01
+with extended comments to code

blinker01_alternative/memmap

@@ -0,0 +1,11 @@
+
+MEMORY
+{
+    ram : ORIGIN = 0x8000, LENGTH = 0x10000
+}
+
+SECTIONS
+{
+    .text : { *(.text*) } > ram
+    .bss : { *(.bss*) } > ram
+}

blinker01_alternative/notmain.c

@@ -0,0 +1,77 @@
+
+//-------------------------------------------------------------------------
+//-------------------------------------------------------------------------
+
+// In this example the GPIO 16 is used to blink (you will need extra LED to test it)
+
+extern void PUT32 ( unsigned int, unsigned int );
+extern unsigned int GET32 ( unsigned int );
+extern void dummy ( unsigned int );
+
+#define GPFSEL3 0x2020000C
+#define GPFSEL4 0x20200004
+#define GPSET1  0x2020001C // would be probably better to call this one CLR
+#define GPCLR1  0x20200028 // and this one SET (see below comments)
+
+// see VII. DIE SPEZIELLE HARDWARE
+// https://uol.de/f/2/dept/informatik/ag/svs/download/reader/reader-seminar-ws2013.pdf
+
+// Translation to english:
+
+// To use these Pins you only need the proper addresses, that start at
+// ”0x20200000“. Each address is made up from 4 Bytes, each pin occupies 3 bits. These
+// Bits specify, what function the pin will have. Thereby the value ”000“ stands for Input and
+// "001“ for output. The 30th and 31st bits are reserved. So the address ”0x20200000“ is for Pins 0-9 and 
+// "0x20200004“ is for Pins 10-19. Up to the address ”0x20200014“ for Pins 50-53. ...
+//
+// 30 and 31 are reserved, then follow tripples for each of the pins (ex. 0-9):
+// |..|...|...|...|...|...|...|...|...|...|...|   pins 0-9   starting at 0x20200000
+// |..|...|...|...|...|...|...|...|...|...|...|   pins 10-19 starting at 0x20200004
+// |..|...|...|...|...|...|...|...|...|...|...|   pins 20-29 starting at 0x20200008
+// |..|...|...|...|...|...|...|...|...|...|...|   pins 30-29 starting at 0x2020000C
+// |..|...|...|...|...|...|...|...|...|...|...|   pins 40-49 starting at 0x20200010
+// |..|...|...|...|...|...|...|...|...|...|...|   pins 50-59 starting at 0x20200014
+//
+// If the pin ist set as OUT, it does not send any signal jet.
+// Sending signal happens first when the address ”0x20200028“ for Pins 0 - 31 bzw.
+// othwewise ”0x2020002C“ fur Pins 32 - 53 for each bit is set to 1 ...
+// To disable it the addresses ”0x2020001C“ otherwise. ”0x20200020“ are used...
+
+//-------------------------------------------------------------------------
+int notmain ( void )
+{
+    unsigned int ra;
+
+    // Set the 16th GPIO to OUT:
+    ra=GET32(GPFSEL4);
+    ra&=~(7<<18); // first cleaning the 3 bits
+    ra|=(1<<18);  // then setting 1 to denote OUT
+    PUT32(GPFSEL4,ra);
+    int * p;
+
+    while(1)
+    {
+        // also here is another way tested to set the value without asm:
+        p = (int*)(GPSET1); *p = (1<<(16));
+        for(ra=0;ra<0x100000;ra++) dummy(ra);
+        p = (int*)(GPCLR1); *p = (1<<(16));
+        for(ra=0;ra<0x100000;ra++) dummy(ra);
+    }
+
+    return(0);
+}
+//-------------------------------------------------------------------------
+//-------------------------------------------------------------------------
+
+
+//-------------------------------------------------------------------------
+//
+// Copyright (c) 2015 David Welch dwelch@dwelch.com
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+//
+//-------------------------------------------------------------------------

blinker01_alternative/notmain.list

@@ -0,0 +1,84 @@
+
+notmain.elf:     file format elf32-littlearm
+
+
+Disassembly of section .text:
+
+00008000 <_start>:
+    8000:	e3a0d902 	mov	sp, #32768	; 0x8000
+    8004:	eb000005 	bl	8020 <notmain>
+
+00008008 <hang>:
+    8008:	eafffffe 	b	8008 <hang>
+
+0000800c <PUT32>:
+    800c:	e5801000 	str	r1, [r0]
+    8010:	e12fff1e 	bx	lr
+
+00008014 <GET32>:
+    8014:	e5900000 	ldr	r0, [r0]
+    8018:	e12fff1e 	bx	lr
+
+0000801c <dummy>:
+    801c:	e12fff1e 	bx	lr
+
+00008020 <notmain>:
+    8020:	e92d4070 	push	{r4, r5, r6, lr}
+    8024:	e59f0054 	ldr	r0, [pc, #84]	; 8080 <notmain+0x60>
+    8028:	ebfffff9 	bl	8014 <GET32>
+    802c:	e3c01707 	bic	r1, r0, #1835008	; 0x1c0000
+    8030:	e3811701 	orr	r1, r1, #262144	; 0x40000
+    8034:	e59f0044 	ldr	r0, [pc, #68]	; 8080 <notmain+0x60>
+    8038:	ebfffff3 	bl	800c <PUT32>
+    803c:	e3a06801 	mov	r6, #65536	; 0x10000
+    8040:	e59f503c 	ldr	r5, [pc, #60]	; 8084 <notmain+0x64>
+    8044:	e3a04000 	mov	r4, #0
+    8048:	e585601c 	str	r6, [r5, #28]
+    804c:	e1a00004 	mov	r0, r4
+    8050:	e2844001 	add	r4, r4, #1
+    8054:	ebfffff0 	bl	801c <dummy>
+    8058:	e3540601 	cmp	r4, #1048576	; 0x100000
+    805c:	1afffffa 	bne	804c <notmain+0x2c>
+    8060:	e3a04000 	mov	r4, #0
+    8064:	e5856028 	str	r6, [r5, #40]	; 0x28
+    8068:	e1a00004 	mov	r0, r4
+    806c:	e2844001 	add	r4, r4, #1
+    8070:	ebffffe9 	bl	801c <dummy>
+    8074:	e3540601 	cmp	r4, #1048576	; 0x100000
+    8078:	1afffffa 	bne	8068 <notmain+0x48>
+    807c:	eafffff0 	b	8044 <notmain+0x24>
+    8080:	20200004 	eorcs	r0, r0, r4
+    8084:	20200000 	eorcs	r0, r0, r0
+
+Disassembly of section .ARM.attributes:
+
+00000000 <.ARM.attributes>:
+   0:	00002a41 	andeq	r2, r0, r1, asr #20
+   4:	61656100 	cmnvs	r5, r0, lsl #2
+   8:	01006962 	tsteq	r0, r2, ror #18
+   c:	00000020 	andeq	r0, r0, r0, lsr #32
+  10:	4d524105 	ldfmie	f4, [r2, #-20]	; 0xffffffec
+  14:	54347620 	ldrtpl	r7, [r4], #-1568	; 0xfffff9e0
+  18:	08020600 	stmdaeq	r2, {r9, sl}
+  1c:	12010901 	andne	r0, r1, #16384	; 0x4000
+  20:	15011404 	strne	r1, [r1, #-1028]	; 0xfffffbfc
+  24:	18031701 	stmdane	r3, {r0, r8, r9, sl, ip}
+  28:	Address 0x0000000000000028 is out of bounds.
+
+
+Disassembly of section .comment:
+
+00000000 <.comment>:
+   0:	3a434347 	bcc	10d0d24 <notmain+0x10c8d04>
+   4:	35312820 	ldrcc	r2, [r1, #-2080]!	; 0xfffff7e0
+   8:	332e363a 			; <UNDEFINED> instruction: 0x332e363a
+   c:	732b312e 			; <UNDEFINED> instruction: 0x732b312e
+  10:	35326e76 	ldrcc	r6, [r2, #-3702]!	; 0xfffff18a
+  14:	39333033 	ldmdbcc	r3!, {r0, r1, r4, r5, ip, sp}
+  18:	7562312d 	strbvc	r3, [r2, #-301]!	; 0xfffffed3
+  1c:	31646c69 	cmncc	r4, r9, ror #24
+  20:	2e362029 	cdpcs	0, 3, cr2, cr6, cr9, {1}
+  24:	20312e33 	eorscs	r2, r1, r3, lsr lr
+  28:	37313032 			; <UNDEFINED> instruction: 0x37313032
+  2c:	30323630 	eorscc	r3, r2, r0, lsr r6
+	...

blinker01_alternative/notmain.srec

@@ -0,0 +1,11 @@
+S00F00006E6F746D61696E2E737265631F
+S3150000800002D9A0E3050000EBFEFFFFEA001080E5C1
+S315000080101EFF2FE1000090E51EFF2FE11EFF2FE15E
+S3150000802070402DE954009FE5F9FFFFEB0717C0E309
+S31500008030011781E344009FE5F3FFFFEB0168A0E32E
+S315000080403C509FE50040A0E31C6085E50400A0E1EC
+S31500008050014084E2F0FFFFEB010654E3FAFFFF1A4A
+S315000080600040A0E3286085E50400A0E1014084E229
+S31500008070E9FFFFEB010654E3FAFFFF1AF0FFFFEA00
+S30D0000808004002020000020206E
+S705000080007A

blinker01_alternative/vectors.s

@@ -0,0 +1,39 @@
+
+;@ ------------------------------------------------------------------
+;@ ------------------------------------------------------------------
+
+.globl _start
+_start:
+    mov sp,#0x8000
+    bl notmain
+hang: b hang
+
+.globl PUT32
+PUT32:
+    str r1,[r0]
+    bx lr
+
+.globl GET32
+GET32:
+    ldr r0,[r0]
+    bx lr
+
+.globl dummy
+dummy:
+    bx lr
+
+;@-------------------------------------------------------------------------
+;@-------------------------------------------------------------------------
+
+
+;@-------------------------------------------------------------------------
+;@
+;@ Copyright (c) 2012 David Welch dwelch@dwelch.com
+;@
+;@ Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+;@
+;@ The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+;@
+;@ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+;@
+;@-------------------------------------------------------------------------

bootloader10/README

@@ -109,6 +109,8 @@ so to deal with that once downloaded you press the letter g to go or
 run the program.  This way you or at least I dont lose any characters
 from the downloaded program.
 
+**Alternativelly you can use Cutecome GUI interface**
+
 I normally do not deliver binaries.  In this case I have left the
 binary in the root directory as bootloader.img, copy this file to
 your sd card and name it kernel.img.
@@ -145,3 +147,11 @@ if you run into this then just make it bigger as well.
 
     ram : ORIGIN = 0x8000, LENGTH = 0x1000000
 
+**Steps how to use the bootloader**
+
+1. Copy the bootloader image to the SD Card as kernel.img
+(now you will have three files there: bootcode.bin start.elf and kernel.img)
+1. Set the SD card to PI and power up PI
+1. Send the coresponding (ex.blinker) srec file over terminal as plain
+1. Press 'g' key on the keyboard
+(see the contents of the bootloader10/notmain.c)

bootloader10/notmain.c

@@ -22,19 +22,35 @@ extern void uart_flush ( void );
 
 extern void leds_off ( void );
 
+// We receive one character at a time: 0...1 or A...F each represeting half a byte (see srec files)
+// ASCII code for '0' is 110000 and '9' is 111001
+// then follow 7 symbols like ':' and ';'
+// and then the 'A', 'B' ... 'F' (see ASCII table)
+// so we offset the A,B,C symbols ... by 7 positions to have contigeous sequence: ..8,9,A,B,C..
 unsigned int ctonib ( unsigned int c )
 {
     if(c>0x39) c-=7;
     return(c&0xF);
 }
 
+void print(char * text, int len)
+{
+    for (int i = 0; i < len; ++i)
+    {
+        uart_send(text[i]);
+    }
+}
+
+// http://srecord.sourceforge.net/man/man5/srec_motorola.html
+// Checksum: The checksum is an 8-bit field that represents the least significant byte of the one’s complement 
+// of the sum of the values represented by the pairs of characters making up the record’s length, address, and data fields.
 int notmain ( void )
 {
     unsigned int state;
     unsigned int ra;
     unsigned int type;
-    unsigned int count;
-    unsigned int sum;
+    unsigned int count; // number of bytes in the data (including size and CRC)
+    unsigned int sum; // checksum
     unsigned int entry;
     unsigned int addr;
     unsigned int data;
@@ -60,6 +76,8 @@ int notmain ( void )
     addr=0;
     type=0;
     entry=0x00008000;
+
+    int startedDwnld = 0;
     while(1)
     {
         ra=uart_recv();
@@ -71,6 +89,11 @@ int notmain ( void )
                 {
                     sum=0;
                     state++;
+                    if (!startedDwnld)
+                    {
+                        print("Started downloading...\n", 23);
+                        startedDwnld = 1;
+                    }
                 }
                 if((ra=='g')||(ra=='G'))
                 {
@@ -110,7 +133,7 @@ int notmain ( void )
                 }
                 break;
             }
-
+            // Reading size -----------------------------
             case 2:
             {
                 count=ctonib(ra);
@@ -131,6 +154,8 @@ int notmain ( void )
                 state++;
                 break;
             }
+            // Reading address -----------------------------
+            // read 8 positions each representing half a byte totalling to 32 bit address
             case  4:
             case  6:
             case  8:
@@ -144,14 +169,6 @@ int notmain ( void )
             case  5:
             case  7:
             case  9:
-            {
-                count--;
-                addr<<=4;
-                addr|=ctonib(ra);
-                sum+=addr&0xFF;
-                state++;
-                break;
-            }
             case 11:
             {
                 count--;
@@ -161,6 +178,7 @@ int notmain ( void )
                 state++;
                 break;
             }
+            // Reading data -----------------------------
             case 12:
             {
                 data=ctonib(ra);
@@ -178,6 +196,7 @@ int notmain ( void )
                     if(type==7)
                     {
                         entry=addr;
+                        print("Download completed!\n", 20);
                     }
                     sum&=0xFF;
                     if(sum!=0xFF)