Bootloader Development
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Contents
Concepts
- Programming with ICSP is useful when the target board is produced in batch. The producer can download a program even when the chip is on the target board.
- However, ICSP requires an external programmer.
- To allow the user to change the program after production but without the need of an external programmer, bootloader becomes useful.
- Bootloader is a small program installed via ICSP. Everytime the device is reset, the bootloader is run first. The bootloader first detects the default serial channel whether the user wishes to download a new program to the device. If so, the bootloader will pause there, and wait for the user to download the hex file from the PC. The hex file is written to the device via RTSP instructions in the bootloader. If a new download is not necessary, the bootloader redirects to the previously installed user's program.
- The disadvantage of bootloaders is that they consume some of the memory of the device.
| Developer | Source | Platform | User Guide | Remarks |
|---|---|---|---|---|
| ingenia | Assembly | Windows |
| |
| Tiny | Assembly | Windows | Web |
|
| Elektronika | Hex | Windows | txt |
|
dsPicBootloader
- The bootloader developed by ingenia is open source and it has been modified (see below) to suit our development using dsPic30f5011.
- Repository for download: here
- Download projects: "dspic_bootloader" and "intel_hex_parser"
- The bootloader (hereafter called dsPicBootloader) employs the following settings:
- Use U2ART channel
- Use FRC, PLL16
- For 5011, the bootloader is located between 0x00AE00 to 0x00AFFE (512bytes). Refer to C:\Program Files\Ingenia\ingeniadsPICbootloader\ibl_dspiclist.xml after installing the GUI interface.
- Changes made to assembly code includes:
1. including p30f5011.gld and p30f5011.inc
.include "p30f5011.inc"
2. changing the config code of UART #0x8420 -> #0x8020
; Uart init
mov #0x8020, W0 ; W0 = 0x8020 -> 1000 0000 0010 0000b
mov W0, U2MODE ; Enable UART, AutoBaud and 8N1
clr U2STA
3. changing the start address 0xAE00 - 0x0100 = 0AD00
.equ CRC, W4
.equ ACK, 0x55
.equ NACK, 0xFF
.equ USER_ADDRESS, 0x0100
.equ START_ADDRESS, 0xAD00 ; Relative to 0x0100
4. using Internal FRC and PLL16
config __FOSC, CSW_FSCM_OFF & FRC_PLL16 ;Turn off clock switching and
;fail-safe clock monitoring and
;use the Internal Clock as the
;system clock
5. disabling MCLR (optional)
config __FBORPOR, PBOR_ON & BORV_27 & PWRT_16 & MCLR_DIS
;Set Brown-out Reset voltage and
;and set Power-up Timer to 16msecs
6. changing all the related registers of U1ART to U2ART, all U1XXX => U2XXX
U2MODE, U2STA, U2BRG, U2RXREG, U2TXREG
7. changing all the related registers of IC1 to IC2, all IC1XXX => IC2XXX
IC2CON, #IC2IF, #IC2IE
dsPicProgrammer (Java-based Multi-Platformed)
- Ingenia developed a programmer (PC-side) that works only in Windows environment. The project for Linux environment is currently suspended.
- A simple programmer (hereafter called dsPicProgrammer) written in Java based on the library developed by RXTX has been developed here. The programmer supports both Linux and Windows environments, and may be used as a substitution for the official programmer developed by ingenia.
- Repository for download: here
- Download project: "dspicProgrammer"
- The programmer has the following specification and limitations:
- Can be used on both Linux and Windows platforms.
- Adjustable baudrate (9600bps to 57600bps[1]).
- Support programming of dsPIC30F5011 and dsPIC33FJ128GP306[2] devices (Developers may add your devices).
- Protection against overwriting bootloader codes on devices.
- Detection if application program does not have its reset() at user's code start address.
- Reprogramming can be done without powering down the target board, provided the user's program is compliant to that stated below.
- Target board will run the user's program after programming is done.
- Can be used with USB-Serial Cables. Below is a list of tested cable:
NOTE:
[1] from version 1.5.2 onwards, the baudrate is increased to 115200bps.
[2] only dsPIC30 devices are compatible with the ingenia's programmer. For dsPIC33 devices, the protocol has been modified due to the increased flash size, and the dsPIC33 bootloader can only work with dsPicProgrammer.
Special Consideration
- The bootloader assumes that the user program starts at address 0x100. This is usually the case, but there are always exceptions.
- To ensure that the user program always starts at address 0x100, you can create a customized linker script and customized reset() function as follows:
- Copy and modify the file named "crt0.s" from the directory "C:\Program Files\Microchip\MPLAB C30\src\pic30" to the project directory and include it.
.section .reset, code //previously .section .libc, code
- Copy and modify the linkerscript for the device (e.g. p30f5011.gld) to the project directory and include it.
.text __CODE_BASE :
{
*(.reset); //<-insert this line here
*(.handle);
*(.libc) *(.libm) *(.libdsp); /* keep together in this order */
*(.lib*);
*(.text);
} >program
Communication Protocol
+-------------------+ +-------------------+----------------+
| dsPicProgrammer | | dsPicBootloader | User's Program |
+-------------------+ +-------------------+----------------+
| PC | | Target dsPic |
+-------------------+ +------------------------------------+
| COM PORT |=============| UART |
+-------------------+ +------------------------------------+
- Stage 1: User's Configuation
- Select a COM port channel
- Select a baudrate
- Select the user hex file
java -jar dsPicProgrammer.jar COM1 19200 foo.hex
- Stage 2: Resetting Target Device
- dsPicProgrammer sends a Break character (pull UART-TX to low logic, which is normally high).
- User's program on dsPic detects the break character and reset the chip
- NOTE: The user's program is expected to have the following code in order to enable this function. Otherwise, the target board must be restarted manually.
void _ISR _U2RXInterrupt(void)
{
//No Framming error
if( U2STAbits.FERR == 0)
{
//Normal procedure
}
//Framming error
else
{
if ( U2STAbits.URXDA ){
unsigned char data;
data = (unsigned char) U2RXREG;
if(data == 0x00){
// A break char has been received:
// U2RX has been pulled to zero for more than 13 bits
// This is used to reboot the pic
mdelay(800); //wait for break character to clear
asm("reset"); //software reset
}
}
}
_U2RXIF = 0; //Clear the flag
}
- Stage 3: Entering Ingenia's Protocol
- Transmission is conducted in 8N1, i.e. 8-bit, no parity, 1 stop-bit
- Communication Protocol is reviewed in ingenia bootloader user's guide section 2.1.3. The following summarises the key steps on the PC side (Refer also to section 2.2.2).
- Autobaud rate detection: dsPicProgrammer continuously sends a character "U" [0x55] via COM port and waits for an acknowledgment character "U", [ACK] = [0x55]
- Version Control: dsPicProgrammer sends the command character [0x03]. On success, dsPicProgrammer receives 3 characters i) Major Version ii) Minor Version iii) Acknowledgment [0x55]
- Device ID Monitoring: dsPicProgrammer sends the read command character [0x01] + 24-bit address [High][Medium][Low] (0xFF0000). Then, it receives 4-byte data [High][Medium][Low][ACK]
- Load the user hex file and check integrity
- Start Programming: dsPicProgrammer issues the write command character [0x02] + 24-bit address [High][Medium][Low]+ Number of bytes [N] + [data 0] + [data 1] + ... + [data N-1] + [CRC]=(INTEL HEX8 Checksum - Sum modulo 256) and receives [ACK] or [NACK] = [0xFF]
- NOTE: Writing is in row mode access (i.e. erase and write a whole row, each row has 32 instructions, or 96 bytes because each instruction has 24 bits)
- Stage 4: Goto User's Program
- dsPicProgrammer sends the goto user code command [0x0F]
