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--- arduino:arduino_without_a_bootloader [2020/02/27 18:13] – [Blessed is the bootloader] mithat
+++ arduino:arduino_without_a_bootloader [2020/06/22 19:49] – old revision restored (2020/02/27 18:23) mithat
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 ===== Cursed is the bootloader =====
-There are times when you might want to bypass the convenience a bootloader offers and program your microcontroller directly. The most common reason is that you want to be able to use //all// of the available flash storage for your program. Bootloaders in ATmega chips are stored in the same flash memory as "user programs." While the amount of required memory is small---for example, the [[https://github.com/Optiboot/optiboot|Optiboot]] bootloader used in common Arduinos is a mere 512 bytes---sometimes you just need to use every last byte of flash on the micro for your program.
+In spite of the convenience a bootloader offers, there are times when you might want to forego this and program a microcontroller directly. The most common reason is that you want to be able to use //all// of the available flash storage for your program. Bootloaders in ATmega chips are stored in the same flash memory as "user programs." While the amount of required memory is small---for example, the [[https://github.com/Optiboot/optiboot|Optiboot]] bootloader used in common Arduinos is a mere 512 bytes---sometimes you just need to use every last byte of flash on the micro for your program.
-Another reason to not use a bootloader is that your project's startup time is critical. The Arduino bootloader introduces about a second and a half delay between power-up/reset and running your program. Without a bootloader, your code starts running almost instantaneously.
+Another reason to not use a bootloader is that the startup time is critical. The Arduino bootloader introduces about a second and a half delay between power-up/reset and running your program. Without the bootloader, your code starts running almost instantaneously.
 Yet another situation where you might not want a bootloader is if you have lowered or disabled the [[https://microchipdeveloper.com/8avr:bod|Brown-Out Detection]] so you can use every last ounce of battery juice in a portable application.((Disabling brown-out detection or lowering the threshold of detection involves [[arduino:atmega328p_arduinos_and_custom_fuse_settings|custom fuse settings]] and is beyond the scope of this article.)) Without brown-out detection, the erratic system behavior you can expect at very low voltages could cause a program jump to an arbitrary part of the code in flash storage. If you use a bootloader, this could be a jump into bootloader code. This then has the potential to start a cascade of events that leads to the bootloader overwriting your program code. If you're not using a bootloader, the code you have programmed can't be corrupted this way.((Not using a bootloader in this situation will keep the program memory form becoming corrupted, but EEPROM and other things can still be battered when the voltage falls below the minimum for a given clock frequency. The risks are described more completely in the [[http://ww1.microchip.com/downloads/en/Appnotes/doc1051.pdf|AVR180: External Brown-out Protection]] application note.))
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 ===== Hardware =====
-You're going to need a device you want to program (e.g., an Arduino board) and a device with which you will do the programming (a.k.a., the programmer). You can see the complete list of programmers supported by the Arduino framework by looking at the list available under //Tools > Programmer: "xxxx"//. At the time of writing this, the available options were:
+To program an ATmega328P without a bootloader, you're going to need a device you want to program (e.g., an Arduino board) and a device with which you will do the programming (i.e., the programmer). You can see the complete list of programmers supported by the Arduino framework by looking at the list available under //Tools > Programmer: "xxxx"//. At the time of writing this, the available options were:
 {{ :arduino:arduino-programmer-options.png?direct |}}
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 That's a lot of options!
-Below, I cover a few cases to get you started. Most of these use the USBtinyISP.((As near as I can tell, the original source of the USBtinyISP design is Dick Streefland's [[https://dicks.home.xs4all.nl/avr/usbtiny/|USBtiny]]. Additional development and refinement leading to the [[https://learn.adafruit.com/usbtinyisp|USBtinyISP]] was done by Limor Fried. The software and hardware are open source (GPL and CC BY-SA 2.5), leading to many clones and derivatives.)) Owing to its low cost and wide availability, this is one of the most popular options. The [[https://learn.adafruit.com/usbtinyisp|original USBtinyISP]] is available sporadically through Adafruit, and clones derived from the open source design similar to [[https://www.ebay.com/itm/USBTiny-USBtinyISP-AVR-ISP-programmer-for-Arduino-bootloader-Meag2560-uno-r3/382580265905|this one]] are widely available at auction sites, Amazon, Banggood, etc. All my testing was done using USBtinyISP clones from two different suppliers.
+Below, I cover a few cases to get you started. Most of these use the USBtinyISP.((As near as I can tell, the original source of the USBtinyISP design is Dick Streefland's [[https://dicks.home.xs4all.nl/avr/usbtiny/|USBtiny]]. Additional development and refinement leading to the [[https://learn.adafruit.com/usbtinyisp|USBtinyISP]] was done by Limor Fried. The software and hardware are open source (GPL and CC BY-SA 2.5), leading to many clones and derivatives.)) Owing to its low cost and wide availability, the USBtinyISP is one of the most popular options. The [[https://learn.adafruit.com/usbtinyisp|original USBtinyISP]] is available sporadically through Adafruit, and clones derived from its open source design along the lines of [[https://www.ebay.com/itm/USBTiny-USBtinyISP-AVR-ISP-programmer-for-Arduino-bootloader-Meag2560-uno-r3/382580265905|this one]] are widely available at auction sites, Amazon, Banggood, etc. All my testing was done using USBtinyISP clones from two different suppliers.
 The original USBtinyISP has a built-in 3x2 IDC cable that carries the signals needed for ISP (in-system programming). It also has a 5x2 IDC cable that carries the same signals but in a different layout.
-If you are using a USBtinyISP clone, there's a good chance it has a keyed 3x2 ISP header in addition to a keyed 5x2 ISP header. The following assumes this is the case and also that you have a 3x2 keyed IDC cable. Such a cable is often included with USBtinyISP clone purchases. Finally, I'm assuming it works at 5VDC, which is the defacto standard.
+If you are using a USBtinyISP clone, there's a good chance it has a keyed 3x2 ISP header in addition to a keyed 5x2 ISP header. The following assumes this is the case and that you have a 3x2 keyed IDC cable. Such a cable is often included with USBtinyISP clone purchases. Finally, I'm assuming it works at 5VDC, which is the defacto standard.
 Depending on the board you are programming, you may need to use Dupont wires (M to F or F to F depending on your USBtinyISP) instead of the IDC cable.