user38088: I am looking for a controller that works with Arduino (i.e. there is official or third-party support for the controller in the Arduino IDE and core libs) and has both built-in CAN and I2C buses. I was looking at the ATMega automotive series (16M1, 32M1, 64M1, 32C1, 64C1) but it does not mention I2C/TWI in the datasheet at all.
(I know I can bitbang I2C, I know there is MCP2515 for CAN over SPI.)
Thanks!
EDIT: The application in mind is a bridge between a few I2C sensors and CAN, no complex logic. High performance is not necessary, plus it will drive costs upwards.

user30175: Many options come to mind:

Bluepill board
Literally any board with I2C and CAN buses from the STM32 series, as searchable on their website (https://my.st.com/content/my_st_com/en/products/microcontrollers.html)
ESP32

A Bluebill board is programmable with mbed, STM32HAL (CubeMX) and Arduino, all of which have either CAN libraries for the CAN peripheral or have it even built-in in the OS (mbedos). 
The Bluepill board is extremely low cost ($1.81 with free shipping from aliexpress) and features an STM32F103C8 microcontroller with 128kB Flash and 20kB RAM. Its peripherals include two I2C and one CAN bus. 


Infos & Datasheet: http://www.st.com/en/microcontrollers/stm32f103c8.html, http://wiki.stm32duino.com/index.php?title=Blue_Pill
For flashing and debugging the chip you should have one cheap ST-Linkv2 clone (~3$ from china). 
For programming environments you can use:

Arduino IDE (STM32Duino Arduino Core for STM32F1/F3/F4 chips: http://wiki.stm32duino.com/index.php?title=Boards_Manager_package)
PlatformIO, more general purpose and more powerful (https://platformio.org:443/boards?count=15&filter%5Bmcu%5D=STM32F103C&page=1&sorting%5Bname%5D=asc)

As frameworks you can use:

Arduino (see above)
ARM mbedos (builds upon STM32HAL, natively supported by PlatformIO)
STM32HAL (e.g. with project files for an IDE generated by STM32CubeMX)

Documentation references:

https://os.mbed.com/docs/v5.8/reference/can.html
https://www.st.com/resource/en/user_manual/dm00154093.pdf (Chapter 8)
https://github.com/Locoduino/Commanders

8 Bit microcontrollers from STM8AF series have a few micros with 1 I2C and 1 CAN bus: See http://www.st.com/en/microcontrollers/stm8af-series.html?querycriteria=productId=SS1583

Ready buyable evaluation board: http://www.st.com/en/evaluation-tools/stm8a-discovery.html (you want the STM8AF5288 one)
The toolchain changes then, of course. See https://my.st.com/content/my_st_com/en/extended-query.html?querycriteria=productId=LN1759$$associatedTo=SS1584

38088: <p>I am looking for a controller that works with Arduino (i.e. there is official or third-party support for the controller in the Arduino IDE and core libs) and has both built-in CAN and I2C buses. I was looking at the ATMega automotive series (16M1, 32M1, 64M1, 32C1, 64C1) but it does not mention I2C/TWI in the datasheet at all.</p>

<p>(I know I can bitbang I2C, I know there is MCP2515 for CAN over SPI.)</p>

<p>Thanks!</p>

<p><strong>EDIT:</strong> The application in mind is a bridge between a few I2C sensors and CAN, no complex logic. High performance is not necessary, plus it will drive costs upwards.</p>
 30175: <p>Many options come to mind:</p>

<ul>
<li>Bluepill board</li>
<li>Literally any board with I2C and CAN buses from the STM32 series, as searchable on their website (<a href="https://my.st.com/content/my_st_com/en/products/microcontrollers.html" rel="nofollow noreferrer">https://my.st.com/content/my_st_com/en/products/microcontrollers.html</a>)</li>
<li>ESP32</li>
</ul>

<p>A Bluebill board is programmable with mbed, STM32HAL (CubeMX) and Arduino, all of which have either CAN libraries for the CAN peripheral or have it even built-in in the OS (mbedos). </p>

<p>The Bluepill board is extremely low cost ($1.81 with free shipping from aliexpress) and features an STM32F103C8 microcontroller with 128kB Flash and 20kB RAM. Its peripherals include two I2C and one CAN bus. </p>

<p><a href="https://i.stack.imgur.com/M0LlQ.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/M0LlQ.png" alt="enter image description here"></a></p>

<p><a href="https://i.stack.imgur.com/yjzq0.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/yjzq0.png" alt="enter image description here"></a></p>

<p>Infos &amp; Datasheet: <a href="http://www.st.com/en/microcontrollers/stm32f103c8.html" rel="nofollow noreferrer">http://www.st.com/en/microcontrollers/stm32f103c8.html</a>, <a href="http://wiki.stm32duino.com/index.php?title=Blue_Pill" rel="nofollow noreferrer">http://wiki.stm32duino.com/index.php?title=Blue_Pill</a></p>

<p>For flashing and debugging the chip you should have one cheap ST-Linkv2 clone (~3$ from china). </p>

<p>For programming environments you can use:</p>

<ul>
<li>Arduino IDE (STM32Duino Arduino Core for STM32F1/F3/F4 chips: <a href="http://wiki.stm32duino.com/index.php?title=Boards_Manager_package" rel="nofollow noreferrer">http://wiki.stm32duino.com/index.php?title=Boards_Manager_package</a>)</li>
<li>PlatformIO, more general purpose and more powerful (<a href="https://platformio.org:443/boards?count=15&amp;filter%5Bmcu%5D=STM32F103C&amp;page=1&amp;sorting%5Bname%5D=asc" rel="nofollow noreferrer">https://platformio.org:443/boards?count=15&amp;filter%5Bmcu%5D=STM32F103C&amp;page=1&amp;sorting%5Bname%5D=asc</a>)</li>
</ul>

<p>As frameworks you can use:</p>

<ul>
<li>Arduino (see above)</li>
<li>ARM mbedos (builds upon STM32HAL, natively supported by PlatformIO)</li>
<li>STM32HAL (e.g. with project files for an IDE generated by STM32CubeMX)</li>
</ul>

<p>Documentation references:</p>

<ul>
<li><a href="https://os.mbed.com/docs/v5.8/reference/can.html" rel="nofollow noreferrer">https://os.mbed.com/docs/v5.8/reference/can.html</a></li>
<li><a href="https://www.st.com/resource/en/user_manual/dm00154093.pdf" rel="nofollow noreferrer">https://www.st.com/resource/en/user_manual/dm00154093.pdf</a> (Chapter 8)</li>
<li><a href="https://github.com/Locoduino/Commanders" rel="nofollow noreferrer">https://github.com/Locoduino/Commanders</a></li>
</ul>

<p>8 Bit microcontrollers from STM8AF series have a few micros with 1 I2C and 1 CAN bus: See <a href="http://www.st.com/en/microcontrollers/stm8af-series.html?querycriteria=productId=SS1583" rel="nofollow noreferrer">http://www.st.com/en/microcontrollers/stm8af-series.html?querycriteria=productId=SS1583</a></p>

<p><a href="https://i.stack.imgur.com/QZpvC.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/QZpvC.png" alt="enter image description here"></a></p>

<p>Ready buyable evaluation board: <a href="http://www.st.com/en/evaluation-tools/stm8a-discovery.html" rel="nofollow noreferrer">http://www.st.com/en/evaluation-tools/stm8a-discovery.html</a> (you want the STM8AF5288 one)</p>

<p>The toolchain changes then, of course. See <a href="https://my.st.com/content/my_st_com/en/extended-query.html?querycriteria=productId=LN1759$$associatedTo=SS1584" rel="nofollow noreferrer">https://my.st.com/content/my_st_com/en/extended-query.html?querycriteria=productId=LN1759$$associatedTo=SS1584</a></p>
