Usage for Tiny PIC bootloader

After you browse or enter the name of the hex file, select the COM port and baud rate:

1. You can keep the TinyBootloader interface opened,  then click WriteFlash, or double-click the tray icon, and after that reset (or power-up) the PIC. If your program is continuously sending serial data to PC, (that will be interpreted as a bootloader response) use the second method:
2. first press PIC reset, click WriteFlash, then release PIC reset;
3. Use a hardware (RTS) or software reset (codes to send first).

Write Flash

Connects to the specified port with the chosen baud rate (both are editable, any value can be typed in) Reads and analyzes the hex file, determines if it's a 16F or 18F code, determine the size, eeprom and config data; check for a goto in the first 4 words, and gives warnings if necessary; Pings the serial port (with the "Code sent by PC for activation") at a rate given by "Timeout" until there is a response from the PIC or until the "SearchDelay" timeout will expire. When a response from the PIC is received the PIC type is identified and the user program written. (no eeprom or config words are written. if needed, this can be done by using one of the available commands).

Commands

Command line parameter: hex filename to be written. When using a command line parameter writing flash will start automatically.

These commands are very rarely used, so it is possible not to work properly for all devices.

Options

List of codes to send first: could be interpreted by a user program as a reset (or activate bootloader command); "SearchDelay" is the amount of time the application will try to contact the pic. "Timeout" is the ping interval; also it acts as a timeout  for all serial operations. If you expect large communication delays, you should increase this (but don't forget to also increase the timeout in tinybld)

Reset could also be performed by hardware, "Reset PIC using RTS line". There are several ways to do it; some require that after reset the RTS should remain low, others prefer "RTS to remain active"

Terminal

	A rudimentary Terminal, with the following possibilities: Display received data as text, hex dump, character codes or graphic. Automatically saves raw data to the specified file (rewrite at every terminal activation). Can send: ascii string one by one characters as you type decimal or hex codes It has a limited (adjustable) display buffer (default 10k)

What do you need

Hardware

• A look at the PIC quick reference could be useful.
• An external programmer is needed (only) the first time in order to write the bootloader into the PIC
• On your board, you must have the PIC (pins TX,RX) connected to the serial port of the PC (pins Rx,Tx), usually using a MAX232 level converter:
  

Bootloader Software

1. You can use one of the provided .hex files or
2. Modify source and assemble it using MPASM IDE
   • PIC16,18: Modify "xtal", "baud", and configuration bits to what you need; assemble it (for example with .\MPLAB\MCHIP_Tools\Mpasmwin.exe);
   • dsPIC: modify "Fcy", "baud" and configuration bits.
3. Write the HEX with a PIC programmer; put the PIC on you board and connect it to the PC serial port.

User Software

The software you write requires no other modification. There are few things to consider:

• If you write your software in assembler the program must have in the first 4 words of memory a GOTO to the start of the main program. This is how most of the ASM programs look anyway. So in assembler it should look something like this:

  PIC16F	PIC16F	PIC18F
  org 0 ;clrf STATUS clrf PCLATH goto Main	org 0 ;clrf STATUS pagesel Main goto Main	org 0 goto Main

• If you use a (C/Basic/...) compiler, some of them may require a special directive to allows coexistence with a bootloader; but then again, most of them will work without specifying anything.

Advanced topics

Modifying it for other devices

1. Verify that the PIC support flash self-write:
   In the datasheet verify that there is a (sub)chapter concerning "Writing to Flash program memory".
2. Find another PIC that has similar features and that has the source code (.asm or .s) available. Open both PIC datasheets, at the chapter referring to Flash Write and make sure that the info referring to erase block size and program block size is the same.
3. In the piccodes.ini file you have to either:
   •  use an existing entry, if you find one that matches the type of PIC and the amount of flash; no modifications will be necessary, just take the id-code (the number in the first column);
   • add a new entry, by adding a new id-code, the type of PIC, a description, amount of flash, amount of eeprom.
   • Hint: look into the datasheet of an existing PIC to see how to write the flash amount;
4. Modify the source for your PIC, using the id-code obtained at the previous step
   • for dsPICs, directly in the source modify: .equ IdTypePIC,ZZZ
   • for PIC16 and 18, make the addition in the icdpictypes.inc file.

Adding more stuff to the bootloader

The bootloader was designed to fit in 96+4 words. On most devices (pic16, pic18) there is almost no room to extend the bootloader by adding more instructions. Extending it is possible by modifting tinybld.ini to use a size of 132 and double that number in asm source.

Critics and suggestions at: