Tag Archives: Leonardo

ArduinoISP on the Due

There may not be a lot of practical value in running ArduinoISP on an Aruino Due. If you have a Due, it is very likely you have at least one classic Arduino at hand for which running ArduinoISP is well known and documented. On the other hand, ArduinoISP is a standard Arduino sample so I find that it should work on any Arduino. Well, it was good fun to make it work…

Due programming bootloader into a Leonardo

Due programming bootloader into a Leonardo

I found an opportunity to start with this when I wanted to upgrade the firmware of my Leonardo

Since Arduino 1.0.3, there is an improved boot loader for Leonardo that is a real must have: upon power-on reset, it jumps immediately to your sketch instead of awaiting programmer commands for some seconds.

Just for the sake of it I decided use my Due for this task.

Due programming an attiny85

Due programming an attiny85

Later on, I tried to program an attiny85. This required some extra measures. The Due’s SPI runs too fast for these targets so I had to use software SPI to slow the Due down.

Wiring, 5V, 3V3…

First thing to take care of was to make sure not to fry the Due which is not 5V tolerant. Connecting it to the ISP port of the Leonardo powered with 5V would probably damage the Due: the Leonardo would drive the MISO signal to 5V. I took a very simple approach: I powered the Leonardo with 3.3V. See red jumper wire between the Due’s 3V3 (don’t accidentally use the adjacent 5V pin) pin and the Leo’s 5V pin.

As usual, my photo’s are lousy, but these are the connections:

Due     | Target (Leonardo, attiny85...)
 SCK    |  SCK
 GND    |  GND
 3.3V   |  Vcc (labeled 5V, on the Leonardo)
 Dig 10 |  RESET

It should be warned not to connect the 5V (!) power pin from the Due’s SPI header to the corresponding pin on the Leonardo (using a flat cable would do this). Like most people on the forum I expected this pin to carry 3V3, and first I was tempted to use it to power the Leonardo. Well it has 5V. OK, trap avoided.

Also when this wiring is in place, don’t connect the Leonardo’s USB cable !

In general, don’t power the target at 5V when doing this.

Get a “Due – ready” version of ArduinoISP

The version of ArduinoISP that comes with the ide is a bit outdated. It does not even compile for the Due because the SPI functionality is implemented using AVR specific SPI registers.

I keep a version here that works on the Due without need for further tweaking, nor patches in the core.

I plan to write more about its details in a later post. It has some options you can configure and it has a few new fixes.

Also for other Arduino’s, this version works out of the box, with a reasonable default configuration. Therefore I think it is a candidate for inclusion in the IDE.  We’ll see…

Edit November 2015: Since Arduino 1.6.6, these modifications are integrated in the IDE.

I wish to thank Sylvan Butler, whose SPI bitbang implementation I started from.

Try it out.

Compile and upload the sketch to your Due. Once that is done it is ready to do ISP. Use the native USB port (see photo).

From this point on, when it comes to programming a target, it makes more sense to use arduino 1.0.x. This is OK, the IDE does not care your ArduinoISP programmer is actually a Due.

Windows users have one more thing to take care of: the ide must be instructed to use “arduino” as programmer instead of “stk500v1”. It is explained here (go to point 7), but looking back on it, I find it more easy to just go into the arduino-1.0.x\hardware\arduino\programmers.txt and change the entry:

That is it. I tested burning the bootloader into my Leonardo using arduino 1.0.3 on linux (Ubuntu 12.04.2 LTS) and on Windows 7 SP1 64bit. I also burned a bootloader into a 328p clocked with16MHz.

It was also possible to burn some led blinking firmwares into an attiny85 clocked@1MHz, internal oscillator.

Modifying the atmega16u2 firmware on the Arduino Due


Flashing new firmware into the Due’s atmega16u2, using a Leonardo as ISP.

Compiling the firmware

The arduino ide comes with the sources for the 16u2’s firmware. It links against  LUFA  (Lightweight USB framework for AVR’s) which you need to download first. Look for version 100807, not the latest one: the 16u2 firmware from the current ide (1.5.2) does not build as is with the latest version of LUFA. Unzip the zip file in any location on your PC.

Locate the 16u2 firmware directory in the arduino install dir: arduino-1.5.2/hardware/arduino/sam/firmwares/atmega16u2/arduino-usbserial. Copy it into LUFA’s Project sub directory, so you end up with a directory LUFA100807/Projects/arduino-usbserial. In that directory, simply type ‘make’.

In a next post I want to present a modified firmware that allows you to disable autoreset on the Due’s programming USB port…

Flashing the new firmware

There is a tutorial on how to flash new firmware in the atmega16u2 on the Due here. However, the wiring used over there uses pins 10, 11, 12 and 13 on the Arduino that serves as programmer. That does not work on the Leonardo. With the info from my first post, it is straightforward to do this task with a Leonardo too. So following diagram does not bring world shocking new information, but I posted it anyway as I found it practical. Pay attention to the orientation of the Due: its isp header is “upside down” as compared to the SPI header.


This wiring works on classic Arduino’s like the Uno or Duemilanove too. I find this one easier to remember and to wire.

The procedure in the official tutorial can be used as is with the Leonardo. Except that there is no need to disable autoreset. The procedure is stable, there is not a lot that can go wrong. And if it fails you can try again. Nevertheless I recommend to first try to download the current firmware from the device, just to verify you have a working isp (e.g. for linux, from the ide’s tools dir):
  ./avrdude -C avrdude.conf -c arduino -P /dev/ttyACM0 -b 19200 -p m16u2 -vvv -U flash:r:old.hex:i

I also recommend to install the three leds. If the sketch hangs somewhere (which happens rarely though), you see immedeately what happened.

I did not connect the 5V pins. Both boards are powered by usb. You can compile a new firmware and after upload, the Leo drives nRESET high and the Due is immedeately ready for action again.

ArduinoISP on the Leonardo

A Leonardo programming an attiny2313

A while ago I noticed this thread about burning an Atmega 328 bootloader with an Arduino Leonardo. It turned out that the ArduinoISP sketch that comes with the arduino ide (version 1.0.1) does not work out of the box on the recent Leonardo model. I decided to buy one and help investigating the problems reported in that thread. Following issues were posted:

In mean time fixes for these issues are committed in the development tree so I expect them to become available in an upcoming release of the ide. Untill then, here is a wrap up on how to use the leonardo as an isp programmer with Arduino 1.0.1. Edit: the fix proposed below in step 3 made it into Arduino 1.0.2, so it is no longer needed. The rest is still applicable.

1. Like in the picture above, connect the target’s MISO/MOSI and SCK signals to the ICSP header of the Leonardo. Don’t connect them to digital pins 11, 12 and 13: on the leo there is no SPI on these pins.

Edit: the picture above is just for setting the scene. Ja450n (thank you) sent me a nice Fritzing drawing, featuring an attiny85,  that is more illustrative:

2. In ArduinoISP.ino, change this line:
#define RESET SS
#define RESET 10

Edit November 2015: Since Arduino 1.6.6 this change is already in the IDE.

This states we want to use pin 10, to reset the target mcu .(the brown wire in the picture).
On the leo, SS is not available on arduino pin 10. Actually it is not available on any arduino pin, the atmega pin that exposes SS is used to drive the RX led. Fortunately it is perfectly ok to use pin 10 (or any other digital pin) to drive the target’s reset. (The only requirement for the SS pin is that it is configured as an output (which makes the leo an SPI master). This requirement is fulfilled since it drives the rx led.

3. Locate the CDC.cpp and USBCore.cpp files in your arduino installation directory and apply following modifications (you may want to make a copy first):
In CDC.cpp, the accept routine should look like this:

void Serial_::accept(void)
    ring_buffer *buffer = &cdc_rx_buffer;

    int i = (unsigned int)(buffer->head+1) % SERIAL_BUFFER_SIZE;

    // if we should be storing the received character into the location
    // just before the tail (meaning that the head would advance to the
    // current location of the tail), we're about to overflow the buffer
    // and so we don't write the character or advance the head.

    // while we have room to store a byte
    while (i != buffer->tail) {
        int c = USB_Recv(CDC_RX);
        if (c == -1)
            break; // no more data, we're done
        buffer->buffer[buffer->head] = c;
        buffer->head = i;

        i = (unsigned int)(buffer->head+1) % SERIAL_BUFFER_SIZE;

In USBCore.cpp, search following snippet:

    USB_Flush(CDC_TX); // Send a tx frame if found
    while (USB_Available(CDC_RX)) // Handle received bytes (if any)

and change it into:

    USB_Flush(CDC_TX); // Send a tx frame if found
    if (USB_Available(CDC_RX)) // Handle received bytes (if any)

4. Compile and upload ArduinoISP to the leo.

5. In the ide, open the serial monitor and see to it that the baud rate is not equal to 1200bps. Close the serial monitor again. This step removes the magic baud rate from the serial port which would cause unintentional auto resets.

6. On linux (and probably mac, though I don’t have a mac to try it) you can just go to the “Tools > Programmer” menu and select “Arduino as ISP” as programmer, Now the leo is ready to act as an isp. From here, follow the regular procedure to burn a bootloader in the target. Or you can use avrdude from the command line to burn any hex file in the target…

7. On windows an extra step is required. When selecting “Arduino as ISP” as programmer, the IDE will invoke avrdude and instruct it to use the stk500v1 protocol. Currently (arduino 1.0.2 and 1.0.3) this does not work on windows. It will result in following error message:

avrdude.exe: Send: 0 [30]   [20]
avrdude.exe: Send: 0 [30]   [20]
avrdude.exe: Send: 0 [30]   [20]
avrdude.exe: Recv:
avrdude.exe: stk500_getsync(): not in sync: resp=0x00

Note that avrdude sends out stuff, but does not receive anything. The leo’s rx led will flash but the tx led stays dark.

As a  temporary work around it was suggested (see here) to define a programmer that instructs avrdude to use the “arduino” protocol instead of “stk500v1”. To do so, create a sub directory named “hardware/leofix” in your sketchbook directory. In that directory install a file “programmers.txt” with following content:

arduinoispleo.name=Arduino as ISP (Leonardo)

After restarting the IDE, you will have an entry “Arduino as ISP (Leonardo)” in the “Tools > Programmers” menu. This will do the job on windows too.

The reason stk500v1 does not work is that upon opening the virtual com port, windows/avrdude do not request to assert the “virtual” DTR and RTS signals. The leonardo refuses to send out data under these conditions so it never writes data back to avrdude. When using the arduino protocol, before starting programming, avrdude will briefly deassert DTR and RTS and assert them again. This would trigger autoreset if you were uploading a sketch to an arduino bootloader. But in this work around, we use the side effect that this leaves DTR/RTS asserted during programming which makes the leonardo talk..

I filed an issue for this too:

8. Another reason why ArduinoISP may not work, may come from the fact that the Leonardo is a composite device (it combines a virtual comm port and a HID (keyboard/mouse) in one USB device). Obviously, if you are on an old operating system that does not support composite devices, ArduinoISP will not work, nor will any sketch that uses USB. (Confusingly, uploading sketches is possible because the boot loader is not a composite device.)

Windows has support from XP SP3 on and from Vista SP1 on, Mac has support since Lion, see here for more background.

Since ArduinoISP does not need the HID stuff, a work around is to build it as a “serial port only” sketch. This is described here.