Device::AVR::UPDI - interact with an AVR microcontroller over UPDI


This module provides a class for interacting with an AVR microcontroller over the UPDI programming and debug interface. This is used by chips in the newer ATmega 0-series, or ATtiny 0-series or 1-series, or AVR DA or AVR DB families.

Hardware Interface

This code expects to find a serial port connected to the UPDI pin of the microcontroller as a shared single-wire interface. Suitable hardware to provide this can be created using a USB-UART adapter, connecting the RX line directly to the MCU's UPDI pin, and connecting TX via a current-limiting resistor of 1kohm.

   +------------+                    +-------------------+
   |         RX-|-------------+      |                   |
   | USB-UART   |             +------|-UPDI              |
   |         TX-|---[ 1k  ]---+      |  ATmega or ATtiny |
   +------------+                    +-------------------|



   $updi = Device::AVR::UPDI->new( ... );

Constructs and returns a new Device::AVR::UPDI instance.

Takes the following named arguments:

dev => STRING

Path to the device node representing the serial port connection.

fh => IO

Alternative to dev, provides an IO handle directly. This should be an instance of IO::Termios, or at least, provide the same interface.

part => STRING

Name of the AVR chip to interact with. This is used to define parameters like memory size and location of internal peripherals.

Any of the following forms are accepted

   part => "ATtiny814"  | "attiny814"  | "t814"
   part => "ATmega4809" | "atmega4809" | "m4809"
   part => "AVR64DA48"  | "avr64da48"
baud => INT

Optional. Overrides the baud rate for communications. Defaults to 115200.

Lower numbers may be useful if communication is unreliable, for example over a long cable or with high capacitance or noise.

After construction, the link must be initialised by calling "init_link" before any of the command methods are used.



   $partinfo = $updi->partinfo;

Returns the Part Info structure containing base addresses and other parameters which may be useful for interacting with the chip.

The returned structure provides the following fields

   $name = $partinfo->name;

   $sig = $partinfo->signature;

   $addr = $partinfo->baseaddr_nvmctrl;
   $addr = $partinfo->baseaddr_fuse;
   $addr = $partinfo->baseaddr_flash;
   $addr = $partinfo->baseaddr_eeprom;
   $addr = $partinfo->baseaddr_sigrow;

   $bytes = $partinfo->pagesize_flash;
   $bytes = $partinfo->pagesize_eeprom;
   $bytes = $partinfo->size_flash;
   $bytes = $partinfo->size_eeprom;

   $fusenames = $partinfo->fusenames;


Returns a data structure containing information about the individual fuse fields defined by this device.

This is parsed directly from a shipped YAML file; see the files in the share/ directory for more details.


The following methods documented in an await expression return Future instances.

   await $updi->init_link;

Initialise the UPDI link for proper communication.

This method must be invoked after the object is constructed, before using any of the other commands.


   $rev = await $updi->read_updirev;

Reads the UPDIREV field of the STATUSA register.


Reads the ASI_SYS_STATUS register.


   $sib = await $updi->read_sib;

Reads the System Information Block.

This is returned in a HASH reference, containing four keys:

      family       => "tinyAVR",
      nvm_version  => "P:0",
      ocd_version  => "D:0",
      dbg_osc_freq => 3,


   $signature = await $updi->read_signature;

Reads the three signature bytes from the Signature Row of the device. This is returned as a plain byte string of length 3.


   await $updi->request_reset( $reset );

Sets or clears the system reset request. Typically used to issue a system reset by momentarilly toggling the request on and off again:

   await $updi->request_reset( 1 );
   await $updi->request_reset( 0 );


   await $updi->erase_chip;

Requests a full chip erase, waiting until the erase is complete.

After this, the chip will be unlocked.

Takes an optional named argument:

no_reset => BOOL

If true, does not issue a system reset request after loading the key. This allows you to load multiple keys at once before sending the reset, which may be required e.g. to recover from a bad SYSCFG0 fuse setting.

   await $updi->erase_chip( no_reset => 1 );
   await $updi->enable_nvmprog;


   await $updi->enable_nvmprog;

Requests the chip to enter NVM programming mode.


   $data = await $updi->read_flash_page( $addr, $len );

Reads a single flash page and returns the data. $addr is within the flash address space.


   await $updi->write_flash_page( $addr, $data );

Writes a single flash page into the NVM controller in 16-bit word transfers. $addr is within the flash address space.


   $data = await $updi->read_eeprom_page( $addr, $len );

Reads a single EEPROM page and returns the data. $addr is within the EEPROM address space.


Similar to "write_flash_page" but issues a combined erase-and-write command and $addr is within the EEPROM address space.


   await $updi->write_fuse( $idx, $value );

Writes a fuse value. $idx is the index of the fuse within the FUSES memory segment, from 0 onwards.


   $value = await $updi->read_fuse( $idx );

Reads a fuse value. $idx is the index of the fuse within the FUSES memory segment, from 0 onwards.



Paul Evans <>