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Help regarding Max 232 PIC programmer Please

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sudheera

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hello friends... I have some problems with a circuit I'm building.. The circuit displays below... The problem is when I'm connect this via serial port the software wouldn't detect the device..I tried so many softwares.. Please can anybody help me..

max232.png
 

john blue

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Hi,

You cannot connect max232 to PIC to work as a programmer. Those mentioned that max232 programmer actually has some bootloader on to the PIC already. :)

---------- Post added at 11:05 ---------- Previous post was at 11:05 ----------

If you need some low cost programmer look for pickit 2
 

sudheera

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thanx for the reply... Can I turn this circuit to a programmer anyway...?
 

john blue

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unless your PIC is preloadedwith bootloader. but, to do that you need a programmer. Why not just build pickit 2 lite. should be sufficient if you need to program 5V devices
 

sudheera

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Oops... yeah I can use It..But here's the problem.. I've already finished the making this circuit..I made a PCB and almost finished the rest.. Can you explain about this boot-loader thing little..I really appreciate your help..
 

ckshivaram

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every controller has a pre developed software developed by manufacturer that acts as initial intelligence to the controller, this bootloader initially checks all the hardware peripherals and sees if the hardware is functional. it also checks the memory and tells the controller whetherwhen it should go to programming mode or execute the program...
 

sudheera

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Thank you all for supporting..One last thing.. can you present specific set of steps to set this bootloader thing please...?
 

ckshivaram

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Boot loader is a [iece of software which is executed only under 2 conditions
1. Power ON
2. Hardware reset

1. As a first step, the bootloader gets programmed in the program memory. A good location for the bootloader is the end of the memory space, but a little part of it will always have to be at the first address location, as the bootloader will have to start running when the micro comes out of reset:
2. the watch dog timer is set.
2. Once the bootloader is in place, and the micro comes out of reset, The bootloader can execute the ISP command handler or the user application code.
3. the bootloader will initialise the internal peripherals of the controller, and will check if they are working properly or not.
4. then it will check the RAM and ROM memory.
5. check if the watch dog is set or underflow.
6. if it has underflown then user program is executed check if a valid user program exists.
7. if WDT is not set or underflown then it enters ISP mode and prepares controller in programming mode.
8. It runs the auto baud rate generator for downloading the hex file from system.
9. check if the auto baud rate is successful, if yes receive the hex file and store it inside, or else go and run the auto baud rate again.
10. after download is over it waits for user reset and then finds a valid user code and executes it.

then it would make the default UART into execution mode. the bootloader will start listening to one of the micro interfaces (like UART, SPI, I2C, CAN etc) for incoming bytes. Sometimes, “listening” might not be the proper way to describe this, as the bootloader might need to generate some clock pulses on the SPI clock line, or it would have to initiate the I2C protocol. If data does come through in the format expected by the bootloader, it starts writing the incoming bytes in the program memory. However, due to the fact that a few locations at the reset vector are occupied by the bootloader code itself, the data of the incoming program that would normally be written there will have to be relocated at a known address

Once the whole incoming program has been written to the flash program memory, the bootloader will execute a jump at the known address , and the program that was sent to the micro will start running. In case no data will came through the intended interface, the bootloader will wait for a while, and then execute the jump to the known address anyway, based on the supposition that the user just wants to run a program that was already burned in the program memory at a previous stage.
 

sudheera

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thank you very much for the info.But I needed to know about how to load this bootloader into the PIC for the first time.
 

sudheera

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18F452 . The circuit I'm using, mention above..
 

ckshivaram

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