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== (**COPIED FROM ENGLISH PAGE**) === Action =

Instruct the compiler to create a boot loader at the specified address.

Can be used for all AVR that support a boot loader like ATMEGA and ATXMEGA chips.

 

= Syntax =

$LOADER = address

 

= Remarks =
<div style="padding: 0px; margin: 0px 0px 0px 4px;">
{| width="604" cellspacing="0" cellpadding="1" border="1" style="border: 2px solid rgb(0, 0, 0); border-spacing: 0px; border-collapse: collapse;"
|- style="vertical-align: top;"
| valign="top" width="15%" style="width: 88px; border: 1px solid rgb(0, 0, 0);" |
address

| valign="top" width="97%" style="width: 507px; border: 1px solid rgb(0, 0, 0);" |
The address where the boot loader is located. You can find this address in the data sheet.

|}
</div>
 

A lot of AVR microcontrollers are configured such that it is possible to use a boot

loader able to receive firmware updates and to reprogram the Flash memory on

demand.

These AVR which support boot loader have a so called boot section.

Normally a chip will start at address 0 when it resets.

This is also called the reset vector.

Chips that have a boot section, split the flash memory in two parts. The boot section is a small part of the normal flash and by setting a fuse bit you select that the chip runs code at the boot sector when it resets instead of the normal reset vector.

 

The Program Flash memory space of ATXMEGA chips is also divided into Application and Boot sections. Both sections

have dedicated Lock Bits for setting restrictions on write or read/write operations.

 

ATXMEGA Program Flash memory parts:
<div style="padding: 0px; margin: 0px;">
{| border="0" cellpadding="0" cellspacing="0"
|- valign="baseline" style="vertical-align: baseline;"
| width="15" | 1.
| Application Section for application code
|}
</div><div style="padding: 0px; margin: 0px;">
{| border="0" cellpadding="0" cellspacing="0"
|- valign="baseline" style="vertical-align: baseline;"
| width="15" | 2.
| Application Table Section for application code or data storage
|}
</div><div style="padding: 0px; margin: 0px;">
{| border="0" cellpadding="0" cellspacing="0"
|- valign="baseline" style="vertical-align: baseline;"
| width="15" | 3.
| Boot Section for application code or bootloader code
|}
</div>
 

 

[[File:Notice.jpg|left|Notice.jpg]]You need to set the fuse bits so the chip jump to the boot loader address at reset (BOOTRST) !

 

Some chips also have fuse bits to select the size of the boot loader (e.g. 1024 words, 2048 words, 4096 words)

 

The boot loader start address depends also on the boot size.

You can find following information in the data sheet of the device (example for ATMEGA644):

 
<div style="padding: 0px; margin: 0px;">
{| id="644" cellspacing="0" cellpadding="0" border="0" style="border: none; border-spacing: 0px;"
|- style="vertical-align: top;"
| valign="top" width="118" style="width: 118px;" |
Boot Size

| valign="top" width="196" style="width: 196px;" |
Boot Loader Flash Section

| valign="top" width="295" style="width: 295px;" |
Boot Reset Address (Start Boot Loader Section)

|- style="vertical-align: top;"
| valign="top" width="118" style="width: 118px;" |
512 words

| valign="top" width="196" style="width: 196px;" |
0x7E00 - 0x7FFF

| valign="top" width="295" style="width: 295px;" |
$loader = $7E00

|- style="vertical-align: top;"
| valign="top" width="118" style="width: 118px;" |
1024 words

| valign="top" width="196" style="width: 196px;" |
0x7C00 - 0x7FFF

| valign="top" width="295" style="width: 295px;" |
$loader = $7C00

|- style="vertical-align: top;"
| valign="top" width="118" style="width: 118px;" |
2048 words

| valign="top" width="196" style="width: 196px;" |
0x7800 - 0x7FFF

| valign="top" width="295" style="width: 295px;" |
$loader = $7800

|- style="vertical-align: top;"
| valign="top" width="118" style="width: 118px;" |
4096 words

| valign="top" width="196" style="width: 196px;" |
0x7000 - 0x7FFF

| valign="top" width="295" style="width: 295px;" |
$loader = $7000

|}
</div>
 

For ATXMEGA chips like ATXMEGA32A4 the boot section is part of the Flash Program Memory.

You can find following information in the data sheet of the ATXMEGA device under Flash Program Memory

(example for ATxmega16A4 .....ATxmega128A4):

 
<div style="padding: 0px; margin: 0px;">
{| id="644" cellspacing="0" cellpadding="0" border="0" style="border: none; border-spacing: 0px;"
|- style="vertical-align: top;"
| valign="top" width="118" style="width: 118px;" |
Chip

| valign="top" width="196" style="width: 196px;" |
Boot Loader Flash Section

| valign="top" width="295" style="width: 295px;" |
Boot Reset Address (Start Boot Loader Section)

|- style="vertical-align: top;"
| valign="top" width="118" style="width: 118px;" |
ATxmega16A4

| valign="top" width="196" style="width: 196px;" |
0x2000 - 0x7FFF

| valign="top" width="295" style="width: 295px;" |
$loader = &H2000

|- style="vertical-align: top;"
| valign="top" width="118" style="width: 118px;" |
ATxmega32A4

| valign="top" width="196" style="width: 196px;" |
0x4000 - 0x47FF

| valign="top" width="295" style="width: 295px;" |
$loader = &H4000

|- style="vertical-align: top;"
| valign="top" width="118" style="width: 118px;" |
ATxmega64A4

| valign="top" width="196" style="width: 196px;" |
0x8000 - 0x87FF

| valign="top" width="295" style="width: 295px;" |
$loader = &H8000

|- style="vertical-align: top;"
| valign="top" width="118" style="width: 118px;" |
ATxmega128A4

| valign="top" width="196" style="width: 196px;" |
0x10000 - 0x10FFF

| valign="top" width="295" style="width: 295px;" |
$loader = &H10000

|}
</div>
 

 

[[File:Notice.jpg|left|Notice.jpg]]An external programmer is needed to program the boot loader into the chip. After the fuse bits are set and the boot loader is programmed you do not need the external programmer anymore for this chip (except you want to change the fuse bits).

 

The MCS boot loader sample is a serial boot loader that uses the serial port (USART).

 

With ATXMEGA or with ATMEGA with more then one USART you can choose which USART (COM port) should be used with the boot loader.

 

For example you can use COM7 with an ATXMEGA:

  Config Com7 = 57600 , Mode = Asynchroneous , Parity = None , Stopbits = 1 , Databits = 8       '  Open "COM7:" For Binary As #7  

[[File:Notice.jpg|left|Notice.jpg]]When using another UART as COM1 do not forget to add the Interface number (in this example #7) to all the Serial IO functions like Waitkey(#7) or   Print #7 , Chr(bstatus); in the boot loader example  

The boot loader uses the X-modem checksum protocol to receive the data. (XModem protocol (packet size = 128))

Most terminal emulators can send X-modem checksum.

 

The Boot loader sample can upload both normal flash programs and EEPROM images.

The Boot loader sends a byte with value of 123 to the AVR Boot loader. This boot loader program then enter the boot loader or will jump to the reset vector (0000) to execute the normal flash program.

 

When it receives 124 instead of 123, it will upload the EEPROM.

When you select a BIN file the flash will be uploaded. When you select an EEP file, the EEPROM will be uploaded.

 

The following sample is written so it supports all chips with a boot section.

 

How you need to use this ATMEGA boot loader  example program:

 
<div style="padding: 0px; margin: 0px;">
{| border="0" cellpadding="0" cellspacing="0"
|- valign="baseline" style="vertical-align: baseline;"
| width="15" | 1.
| Uncomment the Chip type and Const Loaderchip you want to use (for example ATMEGA644)
|}
</div>
 

$regfile = "m644def.dat" '$regfile = "m644Pdef.dat" Const Loaderchip = 644

 
<div style="padding: 0px; margin: 0px;">
{| border="0" cellpadding="0" cellspacing="0"
|- valign="baseline" style="vertical-align: baseline;"
| width="15" | 2.
| Double check the baud rate and COM port you want to use
|}
</div><div style="padding: 0px; margin: 0px;">
{| border="0" cellpadding="0" cellspacing="0"
|- valign="baseline" style="vertical-align: baseline;"
| width="15" | 3.
| Compile the boot loader example
|}
</div><div style="padding: 0px; margin: 0px;">
{| border="0" cellpadding="0" cellspacing="0"
|- valign="baseline" style="vertical-align: baseline;"
| width="15" | 4.
| Program it into the chip with an external programmer like AVR ISP MKII
|}
</div><div style="padding: 0px; margin: 0px;">
{| border="0" cellpadding="0" cellspacing="0"
|- valign="baseline" style="vertical-align: baseline;"
| width="15" | 5.
| Select [[MCS Bootloader|MCS Bootloader]] from programmer (select the right COM Port and baud rate)
|}
</div><div style="padding: 0px; margin: 0px;">
{| border="0" cellpadding="0" cellspacing="0"
|- valign="baseline" style="vertical-align: baseline;"
| width="15" | 6.
| compile a new program or example for this chip
|}
</div><div style="padding: 0px; margin: 0px;">
{| border="0" cellpadding="0" cellspacing="0"
|- valign="baseline" style="vertical-align: baseline;"
| width="15" | 7.
| reset the chip
|}
</div>
 

 

Ways to reset the AVR chip:

 

Hardware reset:
<div style="padding: 0px; margin: 0px;">
{| border="0" cellpadding="0" cellspacing="0"
|- valign="baseline" style="vertical-align: baseline;"
| width="15" | 1.
| Hardware Reset switch/button to GND (manual)
|}
</div><div style="padding: 0px; margin: 0px;">
{| border="0" cellpadding="0" cellspacing="0"
|- valign="baseline" style="vertical-align: baseline;"
| width="15" | 2.
| MCS Bootloader can set and reset the DTR or RTS line of serial COM port which can be used to reset the AVR (automatic)
|}
</div>
 

Software Reset:
<div style="padding: 0px; margin: 0px;">
{| border="0" cellpadding="0" cellspacing="0"
|- valign="baseline" style="vertical-align: baseline;"
| width="15" | 1.
| Reset with Watchdog Timer (e.g. setting the Watchdog to 16ms, start it and let it time out)
|}
</div><div style="padding: 0px; margin: 0px;">
{| border="0" cellpadding="0" cellspacing="0"
|- valign="baseline" style="vertical-align: baseline;"
| width="15" | 2.
| With GOTO command (e.g. when ATMEGA644 is used the boot loader start at $7c00 ($loader = $7c00).
|}
</div>
 Then  you  can use:

 GOTO &H7c00

  to jump to the boot loader start.
<div style="padding: 0px; margin: 0px;">
{| border="0" cellpadding="0" cellspacing="0"
|- valign="baseline" style="vertical-align: baseline;"
| width="15" | 3.
| With ATXMEGA there is a special register to reset the ATXMEGA via software. See also topic ATXMEGA
|}
</div><div style="padding: 0px; margin: 0px;">
{| border="0" cellpadding="0" cellspacing="0"
|- valign="baseline" style="vertical-align: baseline;"
| width="15" | 4.
| With MCS Bootloader you can send one or several ASCII character to reset the chip like with string "boot_me". In this case the "boot_me" must be detected in your main application on the AVR and then use for example Watchdog or GOTO to reset the chip.
|}
</div>
 

The boot loader is written to work at a baud rate of 57600. This baud rate works for most chips that use the internal oscillator. But it is best to check it first with a simple program. When you use a crystal you might even use a higher baud rate.

You can change this by changing the baud rate in the boot loader example (take care to use also the same baud rate in the boot loader application (e.g. [[MCS Bootloader|MCS Bootloader]]) on the PC side)

 

Now make a new test program and compile it. Press F4 to start the [[MCS Bootloader|MCS bootloader]]. You now need to reset the chip so that it will start the boot loader section. The boot loader will send a byte with value of 123 and the Bascom boot loader receives this and thus starts the loader process.

 

There will be a stand alone boot loader available too. And the sample will be extended to support other AVR chips with boot section too.

 

[[File:Notice.jpg|left|Notice.jpg]] There is a $BOOT directive too. It is advised to use $LOADER as it allows you to write the boot loader in BASIC.

 

[[File:Important.jpg|left|Important.jpg]]You can not use interrupts in your boot loader program as the interrupts will point to the reset vector which is located in the lower section of the flash. When you start to writing pages, you overwrite this part.

 

[[File:Notice.jpg|left|Notice.jpg]]Take care when Watchdog is enabled by fuse bits and using a boot loader. You need to reset or deactivate the Watchdog in the boot loader example otherwise the firmware upload could be terminated by watchdog reset !

 

[[File:Notice.jpg|left|Notice.jpg]]If you want to analyze the MCU Control and Status Register to know which reset source caused the reset you need to save this register already in the boot loader example because this register will be cleared and it will be always 0 when you check it at start of your application.

 

[[File:Notice.jpg|left|Notice.jpg]]When you use a boot loader it will use space from the available flash memory. The compiler does not know if you use a boot loader or not. When your program exceeds the available space and runs into the boot sector space, it will overwrite the boot loader.

The [[$LOADERSIZE]] directive will take the boot loader size into account so you will get an error when the target file gets too big.

 

 

= Encryption/Decryption with Bootloader: =

You can use for example AES or XTEA ( [[XTEADECODE]], [[XTEAENCODE]] ) in combination with boot loader examples.

There is an AES with boot loader and AVR-DOS example in the ...BASCOM-AVR\SAMPLES\boot     folder (xmega_dos_boot_AES.zip).

 

= See also =

[[$BOOT]] , [[$LOADERSIZE]], [[MCS Bootloader|MCS Bootloader]]

 

 

There is an example for ATMEGA chips and for ATXMEGA Chips:

 

= ATMEGA Example: =

 <source lang="bascomavr">
'----------------------------------------------------------------
' (c) 1995-2009, MCS
' Bootloader.bas
' This sample demonstrates how you can write your own bootloader
' in BASCOM BASIC
' VERSION 2 of the BOOTLOADER. The waiting for the NAK is stretched
' further a bug was resolved for the M64/M128 that have a big page size
'-----------------------------------------------------------------
'This sample will be extended to support other chips with bootloader
'The loader is supported from the IDE

$crystal = 8000000
'$crystal = 14745600
$baud = 57600 'this loader uses serial com
'It is VERY IMPORTANT that the baud rate matches the one of the boot loader
'do not try to use buffered com as we can not use interrupts

'possible return codes of the PC bootloader.exe
' -6005 Cancel requested
' -6006 Fatal time out
' -6007 Unrecoverable event during protocol
' -6008 Too many errors during protocol
' -6009 Block sequence error in Xmodem
' -6016 Session aborted

'$regfile = "m8def.dat"

'Const Loaderchip = 8
'$regfile = "m168def.dat"
'Const Loaderchip = 168

'$regfile = "m16def.dat"
'Const Loaderchip = 16

'$regfile = "m32def.dat"
'Const Loaderchip = 32

'$regfile = "m88def.dat"
'Const Loaderchip = 88

'$regfile = "m162def.dat"
'Const Loaderchip = 162

'$regfile = "m8515.dat"
'Const Loaderchip = 8515

'$regfile = "m128def.dat"
'Const Loaderchip = 128

'$regfile = "m64def.dat"
'Const Loaderchip = 64

'$regfile = "m2561def.dat"
'Const Loaderchip = 2561

'$regfile = "m2560def.dat"
'Const Loaderchip = 2560

'$regfile = "m329def.dat"
'Const Loaderchip = 329

'$regfile = "m324pdef.dat"
'Const Loaderchip = 324

$regfile = "m644def.dat"
'$regfile = "m644Pdef.dat"
Const Loaderchip = 644

#if Loaderchip = 88 'Mega88
$loader = $c00 'this address you can find in the datasheet
'the loader address is the same as the boot vector address
Const Maxwordbit = 5
Config Com1 = Dummy , Synchrone = 0 , Parity = None , Stopbits = 1 , Databits = 8 , Clockpol = 0
#endif

#if Loaderchip = 168 'Mega168
$loader = $1c00 'this address you can find in the datasheet
'the loader address is the same as the boot vector address
Const Maxwordbit = 6
Config Com1 = Dummy , Synchrone = 0 , Parity = None , Stopbits = 1 , Databits = 8 , Clockpol = 0
#endif

#if Loaderchip = 32 ' Mega32
$loader = $3c00 ' 1024 words
Const Maxwordbit = 6 'Z6 is maximum bit '
Config Com1 = Dummy , Synchrone = 0 , Parity = None , Stopbits = 1 , Databits = 8 , Clockpol = 0
#endif
#if Loaderchip = 8 ' Mega8
$loader = $c00 ' 1024 words
Const Maxwordbit = 5 'Z5 is maximum bit '
Config Com1 = Dummy , Synchrone = 0 , Parity = None , Stopbits = 1 , Databits = 8 , Clockpol = 0
#endif
#if Loaderchip = 161 ' Mega161
$loader = $1e00 ' 1024 words
Const Maxwordbit = 6 'Z6 is maximum bit '
#endif
#if Loaderchip = 162 ' Mega162
$loader = $1c00 ' 1024 words
Const Maxwordbit = 6 'Z6 is maximum bit '
Config Com1 = Dummy , Synchrone = 0 , Parity = None , Stopbits = 1 , Databits = 8 , Clockpol = 0
#endif

#if Loaderchip = 8515 ' Mega8515
$loader = $c00 ' 1024 words
Const Maxwordbit = 5 'Z6 is maximum bit '
Config Com1 = Dummy , Synchrone = 0 , Parity = None , Stopbits = 1 , Databits = 8 , Clockpol = 0
Osccal = &HB3 ' the internal osc needed a new value
#endif

#if Loaderchip = 64 ' Mega64
$loader = $7c00 ' 1024 words
Const Maxwordbit = 7 'Z7 is maximum bit '
Config Com1 = Dummy , Synchrone = 0 , Parity = None , Stopbits = 1 , Databits = 8 , Clockpol = 0
#endif

#if Loaderchip = 128 ' Mega128
$loader = &HFC00 ' 1024 words
Const Maxwordbit = 7 'Z7 is maximum bit '
Config Com1 = Dummy , Synchrone = 0 , Parity = None , Stopbits = 1 , Databits = 8 , Clockpol = 0
#endif

#if Loaderchip = 2561 ' Mega2561
$loader = &H1FC00 ' 1024 words
Const Maxwordbit = 7 'Z7 is maximum bit '
Config Com1 = Dummy , Synchrone = 0 , Parity = None , Stopbits = 1 , Databits = 8 , Clockpol = 0
#endif

#if Loaderchip = 2560 ' Mega2560
$loader = &H1FC00 ' 1024 words
Const Maxwordbit = 7 'Z7 is maximum bit '
Config Com1 = Dummy , Synchrone = 0 , Parity = None , Stopbits = 1 , Databits = 8 , Clockpol = 0
#endif

#if Loaderchip = 16 ' Mega16
$loader = $1c00 ' 1024 words
Const Maxwordbit = 6 'Z6 is maximum bit '
Config Com1 = Dummy , Synchrone = 0 , Parity = None , Stopbits = 1 , Databits = 8 , Clockpol = 0
#endif

#if Loaderchip = 329 ' Mega32
$loader = $3c00 ' 1024 words
Const Maxwordbit = 6 'Z6 is maximum bit '
Config Com1 = Dummy , Synchrone = 0 , Parity = None , Stopbits = 1 , Databits = 8 , Clockpol = 0
#endif

#if Loaderchip = 324 ' Mega32
$loader = $3c00 ' 1024 words
Const Maxwordbit = 6 'Z6 is maximum bit '
Config Com1 = Dummy , Synchrone = 0 , Parity = None , Stopbits = 1 , Databits = 8 , Clockpol = 0
#endif

#if Loaderchip = 644 ' Mega644P
$loader = $7c00 ' 1024 words
Const Maxwordbit = 7 'Z7 is maximum bit '
Config Com1 = Dummy , Synchrone = 0 , Parity = None , Stopbits = 1 , Databits = 8 , Clockpol = 0
#endif

Const Maxword =(2 ^ Maxwordbit) * 2 '128
Const Maxwordshift = Maxwordbit + 1
Const Cdebug = 0 ' leave this to 0

#if Cdebug
Print Maxword
Print Maxwordshift
#endif

'Dim the used variables
Dim Bstatus As Byte , Bretries As Byte , Bblock As Byte , Bblocklocal As Byte
Dim Bcsum1 As Byte , Bcsum2 As Byte , Buf(128) As Byte , Csum As Byte
Dim J As Byte , Spmcrval As Byte ' self program command byte value

Dim Z As Long 'this is the Z pointer word
Dim Vl As Byte , Vh As Byte ' these bytes are used for the data values
Dim Wrd As Word , Page As Word 'these vars contain the page and word address
Dim Bkind As Byte , Bstarted As Byte
'Mega 88 : 32 words, 128 pages

Disable Interrupts 'we do not use ints

'Waitms 100 'wait 100 msec sec
'We start with receiving a file. The PC must send this binary file

'some constants used in serial com
Const Nak = &H15
Const Ack = &H06
Const Can = &H18

'we use some leds as indication in this sample , you might want to remove it
Config Pinb.2 = Output
Portb.2 = 1 'the stk200 has inverted logic for the leds
Config Pinb.3 = Output
Portb.3 = 1

$timeout = 400000 'we use a timeout
'When you get LOADER errors during the upload, increase the timeout value
'for example at 16 Mhz, use 200000

Bretries = 5 'we try 5 times
Testfor123:
#if Cdebug
Print "Try " ; Bretries
Print "Wait"
#endif
Bstatus = Waitkey() 'wait for the loader to send a byte
#if Cdebug
Print "Got "
#endif

Print Chr(bstatus);

If Bstatus = 123 Then 'did we received value 123 ?
Bkind = 0 'normal flash loader
Goto Loader
Elseif Bstatus = 124 Then ' EEPROM
Bkind = 1 ' EEPROM loader
Goto Loader
Elseif Bstatus <> 0 Then
Decr Bretries
If Bretries <> 0 Then Goto Testfor123 'we test again
End If

For J = 1 To 10 'this is a simple indication that we start the normal reset vector
Toggle Portb.2 : Waitms 100
Next

#if Cdebug
Print "RESET"
#endif
Goto _reset 'goto the normal reset vector at address 0

'this is the loader routine. It is a Xmodem-checksum reception routine
Loader:
#if Cdebug
Print "Clear buffer"
#endif
Do
Bstatus = Waitkey()
Loop Until Bstatus = 0

For J = 1 To 3 'this is a simple indication that we start the normal reset vector
Toggle Portb.2 : Waitms 50
Next

If Bkind = 0 Then
Spmcrval = 3 : Gosub Do_spm ' erase the first page
Spmcrval = 17 : Gosub Do_spm ' re-enable page
End If

Bretries = 10 'number of retries

Do
Bstarted = 0 ' we were not started yet
Csum = 0 'checksum is 0 when we start
Print Chr(nak); ' firt time send a nack
Do

Bstatus = Waitkey() 'wait for statuse byte

Select Case Bstatus
Case 1: ' start of heading, PC is ready to send
Incr Bblocklocal 'increase local block count
Csum = 1 'checksum is 1
Bblock = Waitkey() : Csum = Csum + Bblock 'get block
Bcsum1 = Waitkey() : Csum = Csum + Bcsum1 'get checksum first byte
For J = 1 To 128 'get 128 bytes
Buf(j) = Waitkey() : Csum = Csum + Buf(j)
Next
Bcsum2 = Waitkey() 'get second checksum byte
If Bblocklocal = Bblock Then 'are the blocks the same?
If Bcsum2 = Csum Then 'is the checksum the same?
Gosub Writepage 'yes go write the page
Print Chr(ack); 'acknowledge
Else 'no match so send nak
Print Chr(nak);
End If
Else
Print Chr(nak); 'blocks do not match
End If
Case 4: ' end of transmission , file is transmitted
If Wrd > 0 And Bkind = 0 Then 'if there was something left in the page
Wrd = 0 'Z pointer needs wrd to be 0
Spmcrval = 5 : Gosub Do_spm 'write page
Spmcrval = 17 : Gosub Do_spm ' re-enable page
End If
' Waitms 100 ' OPTIONAL REMARK THIS IF THE DTR SIGNAL ARRIVES TO EARLY
Print Chr(ack); ' send ack and ready

Portb.3 = 0 ' simple indication that we are finished and ok
Waitms 20
Goto _reset ' start new program
Case &H18: ' PC aborts transmission
Goto _reset ' ready
Case 123 : Exit Do 'was probably still in the buffer
Case 124 : Exit Do
Case Else
Exit Do ' no valid data
End Select
Loop
If Bretries > 0 Then 'attempte left?
Waitms 1000
Decr Bretries 'decrease attempts
Else
Goto _reset 'reset chip
End If
Loop

'write one or more pages
Writepage:
If Bkind = 0 Then
For J = 1 To 128 Step 2 'we write 2 bytes into a page
Vl = Buf(j) : Vh = Buf(j + 1) 'get Low and High bytes
lds r0, {vl} 'store them into r0 and r1 registers
lds r1, {vh}
Spmcrval = 1 : Gosub Do_spm 'write value into page at word address
Wrd = Wrd + 2 ' word address increases with 2 because LS bit of Z is not used
If Wrd = Maxword Then ' page is full
Wrd = 0 'Z pointer needs wrd to be 0
Spmcrval = 5 : Gosub Do_spm 'write page
Spmcrval = 17 : Gosub Do_spm ' re-enable page

Page = Page + 1 'next page
Spmcrval = 3 : Gosub Do_spm ' erase next page
Spmcrval = 17 : Gosub Do_spm ' re-enable page
End If
Next

Else 'eeprom
For J = 1 To 128
Writeeeprom Buf(j) , Wrd
Wrd = Wrd + 1
Next
End If
Toggle Portb.2 : Waitms 10 : Toggle Portb.2 'indication that we write
Return

Do_spm:
Bitwait Spmcsr.0 , Reset ' check for previous SPM complete
Bitwait Eecr.1 , Reset 'wait for eeprom

Z = Page 'make equal to page
Shift Z , Left , Maxwordshift 'shift to proper place
Z = Z + Wrd 'add word
lds r30,{Z}
lds r31,{Z+1}

#if _romsize > 65536
lds r24,{Z+2}
sts rampz,r24 ' we need to set rampz also for the M128
#endif

Spmcsr = Spmcrval 'assign register
spm 'this is an asm instruction
nop
nop
Return

'How you need to use this program:
'1- compile this program
'2- program into chip with sample elctronics programmer
'3- select MCS Bootloader from programmers
'4- compile a new program for example M88.bas
'5- press F4 and reset your micro
' the program will now be uploaded into the chip with Xmodem Checksum
' you can write your own loader.too
'A stand alone command line loader is also available

'How to call the bootloader from your program without a reset ???
'Do
' Print "test"
' Waitms 1000
' If Inkey() = 27 Then
' Print "boot"
' Goto &H1C00
' End If
'Loop

'The GOTO will do the work, you need to specify the correct bootloader address
'this is the same as the $LOADER statement.
</source>

= ATXMEGA Example: =

<source lang="bascomavr">
'----------------------------------------------------------------
' (c) 1995-2009, MCS
' BootloaderXmega32A4.bas
' This sample demonstrates how you can write your own bootloader
' in BASCOM BASIC for the XMEGA
'-----------------------------------------------------------------
'The loader is supported from the IDE
$crystal = 32000000 ' xmega128 is running on 32 MHz
$regfile = "xm32a4def.dat"
$lib "xmega.lib" ' add a reference to this lib

'first enabled the osc of your choice
Config Osc = Disabled , 32mhzosc = Enabled 'internal 2 MHz and 32 MHz enabled

'configure the systemclock
Config Sysclock = 32mhz , Prescalea = 1 , Prescalebc = 1_1 ' we will use 32 MHz and divide by 1 to end up with 32 MHz

$loader = &H4000 ' bootloader starts after the application

Config Com1 = 57600 , Mode = Asynchroneous , Parity = None , Stopbits = 1 , Databits = 8 ' use USART C0
'COM0-USARTC0, COM1-USARTC2, COM2-USARTD0. etc.

Config Portc.3 = Output 'define TX as output
Config Pinc.2 = Input

Const Maxwordbit = 7 ' Z7 is maximum bit '
Const Maxword =(2 ^ Maxwordbit) * 2 '128
Const Maxwordshift = Maxwordbit + 1
Const Cdebug = 0 ' leave this to 0

'Dim the used variables
Dim Bstatus As Byte , Bretries As Byte , Bmincount As Byte , Bblock As Byte , Bblocklocal As Byte
Dim Bcsum1 As Byte , Bcsum2 As Byte , Buf(128) As Byte , Csum As Byte
Dim J As Byte , Spmcrval As Byte ' self program command byte value

Dim Z As Long 'this is the Z pointer word
Dim Vl As Byte , Vh As Byte ' these bytes are used for the data values
Dim Wrd As Word , Page As Word 'these vars contain the page and word address

Disable Interrupts 'we do not use ints

'We start with receiving a file. The PC must send this binary file

'some constants used in serial com
Const Nak = &H15
Const Ack = &H06
Const Can = &H18

$timeout = 300000 'we use a timeout
'When you get LOADER errors during the upload, increase the timeout value
'for example at 16 Mhz, use 200000

Bretries = 5 : Bmincount = 3 'we try 10 times and want to get 123 at least 3 times
Do
Bstatus = Waitkey() 'wait for the loader to send a byte

If Bstatus = 123 Then 'did we received value 123 ?
If Bmincount > 0 Then
Decr Bmincount
Else
Print Chr(bstatus);
Goto Loader ' yes so run bootloader
End If
Else 'we received some other data
If Bretries > 0 Then 'retries left?
Bmincount = 3
Decr Bretries
Else
Rampz = 0
Goto Proces_reset 'goto the normal reset vector at address 0
End If
End If
Loop

'this is the loader routine. It is a Xmodem-checksum reception routine
Loader:
Do
Bstatus = Waitkey()
Loop Until Bstatus = 0

Spmcrval = &H20 : Gosub Do_spm ' erase all app pages

Bretries = 10 'number of retries

Do
Csum = 0 'checksum is 0 when we start
Print Chr(nak); ' firt time send a nack
Do

Bstatus = Waitkey() 'wait for statuse byte

Select Case Bstatus
Case 1: ' start of heading, PC is ready to send
Incr Bblocklocal 'increase local block count
Csum = 1 'checksum is 1
Bblock = Waitkey() : Csum = Csum + Bblock 'get block
Bcsum1 = Waitkey() : Csum = Csum + Bcsum1 'get checksum first byte
For J = 1 To 128 'get 128 bytes
Buf(j) = Waitkey() : Csum = Csum + Buf(j)
Next
Bcsum2 = Waitkey() 'get second checksum byte

If Bblocklocal = Bblock Then 'are the blocks the same?

If Bcsum2 = Csum Then 'is the checksum the same?
Gosub Writepage 'yes go write the page
Print Chr(ack); 'acknowledge
Else 'no match so send nak
Print Chr(nak);
End If
Else
Print Chr(nak); 'blocks do not match
End If
Case 4: ' end of transmission , file is transmitted
If Wrd > 0 Then 'if there was something left in the page
Wrd = 0 'Z pointer needs wrd to be 0
Spmcrval = &H24 : Gosub Do_spm 'write page
End If
Print Chr(ack); ' send ack and ready
Waitms 20
Goto Proces_reset
Case &H18: ' PC aborts transmission
Goto Proces_reset ' ready
Case 123 : Exit Do 'was probably still in the buffer
Case 124 : Exit Do
Case Else
Exit Do ' no valid data
End Select
Loop
If Bretries > 0 Then 'attempte left?
Waitms 1000
Decr Bretries 'decrease attempts
Else
Goto Proces_reset 'reset chip
End If
Loop

'write one or more pages
Writepage:
For J = 1 To 128 Step 2 'we write 2 bytes into a page
Vl = Buf(j) : Vh = Buf(j + 1) 'get Low and High bytes
lds r0, {vl} 'store them into r0 and r1 registers
lds r1, {vh}
Spmcrval = &H23 : Gosub Do_spm 'write value into page at word address
Wrd = Wrd + 2 ' word address increases with 2 because LS bit of Z is not used
If Wrd = Maxword Then ' page is full
Wrd = 0 'Z pointer needs wrd to be 0
Spmcrval = &H24 : Gosub Do_spm 'write page
Page = Page + 1 'next page
End If
Next
Return

Do_spm:
Z = Page 'make equal to page
Shift Z , Left , Maxwordshift 'shift to proper place
Z = Z + Wrd 'add word
lds r30,{Z}
lds r31,{Z+1}

#if _romsize > 65536
lds r24,{Z+2}
sts rampz,r24 ' we need to set rampz also for the M128
#endif

Nvm_cmd = Spmcrval
Cpu_ccp = &H9D
spm 'this is an asm instruction
Do_spm_busy:
lds r23, NVM_STATUS
sbrc r23,7 ;if busy bit is cleared skip next instruc tion
rjmp do_spm_busy
Return

Proces_reset:
Rampz = 0
Goto _reset 'start at address 0

</source> {{Languages}}

[[Category:BASCOM_Language_Reference/de]]

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