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Arduinos (and other AVRs) Write To Own Flash

arduino, arduino hacks, AVR, bootloader, flash memory, optiboot, Programming Commenti disabilitati su Arduinos (and other AVRs) Write To Own Flash 

In this post on the forums and this blog post, [Majek] announced that he had fooled the AVR microcontroller inside and Arduino into writing user data into its own flash memory during runtime. Wow!

[Majek] has pulled off a very neat hack here. Normally, an AVR microcontroller can’t write to its own flash memory except when it’s in bootloader mode, and you’re stuck using EEPROM when you want to save non-volatile data. But EEPROM is scarce, relative to flash.

Now, under normal circumstances, writing into the flash program memory can get you into trouble. Indeed, the AVR has protections to prevent code that’s not hosted in the bootloader memory block from writing to flash. But of course, the bootloader has to be able to program the chip, so there’s got to be a way in.

The trick is that [Majek] has carefully modified the Arduino’s Optiboot bootloader so that it exposes a flash-write (SPM) command at a known location, so that he can then use this function from outside the bootloader. The AVR doesn’t prevent the SPM from proceeding, because it’s being called from within the bootloader memory, and all is well.

The modified version of the Optiboot bootloader is available on [Majek]’s Github.¬† If you want to see how he did it, here are the diffs. A particularly nice touch is that this is all wrapped up in easy-to-write code with a working demo. So next time you’ve filled up the EEPROM, you can reach for this hack and log your data into flash program memory.

Thanks [Koepel] for the tip!

Filed under: Arduino Hacks

Programming an Arduino over WiFi with the ESP8266

arduino hacks, bootloader, ESP8266, optiboot, wifi Commenti disabilitati su Programming an Arduino over WiFi with the ESP8266 

A lot of people have used ESP8266 to add inexpensive WiFi connectivity to their projects, but [Oscar] decided to take it one step further and program an Arduino over WiFi with the ESP8266. [Oscar] wrote a server script in Python that communicates with firmware running on the Arduino. The Arduino connects to the server on startup and listens for a “reboot” command.

When the command is received, the processor resets and enters the bootloader. The python script begins streaming a hex file over WiFi to the ESP8226, which relays it to the Arduino’s bootloader. Once the hex file is streamed, the microcontroller seamlessly starts executing the firmware. This method can be used with any AVR running a stk500-compatible bootloader.

[Oscar]‘s writeup is in Spanish, but fortunately the comments in his Python and Arduino code are in English. Check out the video (in English) after the break where [Oscar] demonstrates his bootloading setup.


Filed under: Arduino Hacks

Programming Micros With Impossibly Cheap Bluetooth Adapters

arduino, arduino hacks, bluetooth, bluetooth programming, optiboot Commenti disabilitati su Programming Micros With Impossibly Cheap Bluetooth Adapters 


[Zenios] and [Raivis] are building a small balancing robot, and for communications to the outside world, they’re using a small, extremely cheap Bluetooth adapter. They figured uploading code to the microcontroller over Bluetooth would be a good idea, but their adapter, a cheap HC-06 module, had no way of resetting the microcontroller; it just provided Tx and Rx the serial port. They did notice a LED blinked when a device wasn’t connected to the adapter, so with a simple circuit¬†they kludged a reset circuit where it wasn’t intended.

The small LED on the HC-06 module blinks when nothing is connected, and remains on when a connection is established. Figuring a new connection would be a good time to upload new code, the guys needed to design a circuit that would stay low when the LED was blinking, and switch to high when the LED was on.

A simple RC filter took care of the blinking LED, keeping the line low until a device connected. Bringing the logic level high when the LED stayed solid required digging through a part drawer, eventually finding an LM741 p differential amplifier.

After a few small changes to the bootloader, the guys had a reliable means of flashing new firmware without the need of programming adapters or wires draped over their workspace, all with a Bluetooth adapter that shouldn’t have this capability. Video below.

Filed under: Arduino Hacks

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