$LOADER
Contents |
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
|
address |
The address where the boot loader is located. You can find this address in the data sheet. |
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:
| 1. | Application Section for application code |
| 2. | Application Table Section for application code or data storage |
| 3. | Boot Section for application code or bootloader code |
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):
|
Boot Size |
Boot Loader Flash Section |
Boot Reset Address (Start Boot Loader Section) |
|
512 words |
0x7E00 - 0x7FFF |
$loader = $7E00 |
|
1024 words |
0x7C00 - 0x7FFF |
$loader = $7C00 |
|
2048 words |
0x7800 - 0x7FFF |
$loader = $7800 |
|
4096 words |
0x7000 - 0x7FFF |
$loader = $7000 |
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):
|
Chip |
Boot Loader Flash Section |
Boot Reset Address (Start Boot Loader Section) |
|
ATxmega16A4 |
0x2000 - 0x7FFF |
$loader = &H2000 |
|
ATxmega32A4 |
0x4000 - 0x47FF |
$loader = &H4000 |
|
ATxmega64A4 |
0x8000 - 0x87FF |
$loader = &H8000 |
|
ATxmega128A4 |
0x10000 - 0x10FFF |
$loader = &H10000 |
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
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:
| 1. | Uncomment the Chip type and Const Loaderchip you want to use (for example ATMEGA644) |
$regfile = "m644def.dat"
'$regfile = "m644Pdef.dat"
Const Loaderchip = 644
| 2. | Double check the baud rate and COM port you want to use |
| 3. | Compile the boot loader example |
| 4. | Program it into the chip with an external programmer like AVR ISP MKII |
| 5. | Select MCS Bootloader from programmer (select the right COM Port and baud rate) |
| 6. | compile a new program or example for this chip |
| 7. | reset the chip |
Ways to reset the AVR chip:
Hardware reset:
| 1. | Hardware Reset switch/button to GND (manual) |
| 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) |
Software Reset:
| 1. | Reset with Watchdog Timer (e.g. setting the Watchdog to 16ms, start it and let it time out) |
| 2. | With GOTO command (e.g. when ATMEGA644 is used the boot loader start at $7c00 ($loader = $7c00). |
Then you can use:
GOTO &H7c00
to jump to the boot loader start.
| 3. | With ATXMEGA there is a special register to reset the ATXMEGA via software. See also topic ATXMEGA |
| 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. |
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) on the PC side)
Now make a new test program and compile it. Press F4 to start the 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.
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
There is an example for ATMEGA chips and for ATXMEGA Chips:
ATMEGA Example:
'---------------------------------------------------------------- ' (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.
ATXMEGA Example:
'---------------------------------------------------------------- ' (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
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