cosduino_bootloader

Costycnc bootloader , cosduino bootloader , costycnc cosduino

A bootloader is just a normal AVR application that is positioned in a special region 

of flash memory. In this project I refer only to the atmega8 !!!!

In sd_boot/sd_boot1.bas file 

$regfile = "m8def.dat"

$crystal = 8000000

$loader = $e00

Means that this programs is write at adress E00 hex adress.This means that when power on or reset atmega8, atmega8 read first time by this adress.

(After execute the boot program ,normally,begin to read and execute from adress 0)

Normally ,without bootloader when power on or reset atmega8 ,atmega8 read and execute data from adress 0! 

In this project, when power on or reset atmega8 the boot program :

- if SDCARD is inserted read data from SDCARD and write program to address 0

-if sdcard is not inserted ... jump to adress 0!

For the beginning only this you need to know about boot !!!

First lines of program is for initialize sdcard...this code below do this !

Config Spi = Hard , Interrupt = Off , Data Order = Msb , Master = Yes , Polarity = Low , Phase = 0 , Clockrate = 64 , Noss = 1 , Spiin = 255

   Spiinit

        sbi portb,2                                         'Set Sd_cs

        Sdcommand = &HFF

        Spiout Sdcommand , 1

        For Sdtempb = 1 To 74

        Gosub Sdcommand1

        Next Sdtempb

        cbi portb,2                                         'Reset Sd_cs

             Sdsectorc = &H40000000

             Sdsectorf = &H0095

             Gosub Sdreadsectortest

             Sdsectorc = &H48000001

             Sdsectorf = &HAA87

             Gosub Sdreadsectortest

              If Sdresponse(1) = &B00000001 Then

             Sdsectorc = &H7A000000

             Sdsectorf = &H00FD

             Gosub Sdreadsectortest

      Do

             Sdsectorc = &H77000000

             Sdsectorf = &H0065

             Gosub Sdreadsectortest

             Sdsectorc = &H69400000

             Sdsectorf = &H0077

             Gosub Sdreadsectortest

             Incr Sdtempw

             Loop Until Sdresponse(1) = 0 Or Sdtempw = &HFFFF

            Gosub Sdresponse2_5

After the card has been initialized you can read from any address from SDCARD!

My bootloader is very small because not use library for find file address of your program from SCARD, so this needs to do it manually.

File is hex or bin program (your aplication!)

In this video see how can find this address on sdcard!

After find this address ,write here ( Sdsectord = your progam address ) 

            Sdsectord = 1651264                             '1239168

            Gosub Sdreadsector

After modify this address you can load this boot program in Microcontroller Atmega8.

You can load with this module:

See here how do it : atmega8_load

This boot program write 12 sectors by SDCARD on flash memory Atmega8 (512x12 = approx 6K  ... 2k is bootloader ... so ,totally is 8k )

This routine write this 12 sectors:

$asm

'Z adresa unde scrie in flash

'Y lungime buffer de scris

'X adresa memorie temporara de scris -- $60

clr r18

clr r19

ldi r22,2

clr r21

ldi r17,$40

Ss1:

ldi xl,$60                                                  'set again X registry to begin data memory ($60)

clr xh

Ss:

rcall write_p

Add R18 , r17

sbic sreg,0

inc r19

cp r19,r22

brne ss

push r16

push r17

push r18

push r19

push r20

push r21

push r22

push r23

push r24

push r25

push r26

push r27

push r28

push r29

push r30

push r31

$end Asm

Incr Sdsectord

Gosub Sdreadsector

$asm

pop r31

pop r30

pop r29

pop r28

pop r27

pop r26

pop r25

pop r24

pop r23

pop r22

pop r21

pop r20

pop r19

pop r18

pop r17

pop r16

inc r22

inc r22

inc r21

cpi r21,12                                                  'poate fi facut 14

brne ss1

$end Asm

End If

jmp 0

And you can see at the end ... JMP 0 instruction ... now you know that's the point of this instruction!

Success!