Summary

• ATtiny824 breakout
• UPDI+ programming header
• Status LED
• Reset button

What is it?

This board holds an AVR ATtiny824 microcontroller, providing access to all of the IO pins. It adds power supply decoupling capacitors, an LED, a button, and UPDI programming header to make a convenient self-contained development board for small microcontroller projects.

The LED is attached to the PA7 pin via a 2k2 current-limiting resistor.

The button is attached to the PA0 UPDI/RESET# pin via a series resistor to prevent damage in case of drive contention. Note that the PA0 pin defaults to UPDI mode. Switching the pin to RESET mode will require the use of a 12V-capable UPDI programmer if you want to program the chip after this.

The board also provides a programming header in the AVR standard 2x3 layout. Note that this will requires a UPDI-capable programmer. An SPI-style ISP programmer will not work with this chip. This programming header also includes the USART.0 TX and RX signals in "UPDI+" layout, allowing single-cable programming and debug with a suitable programmer.

Finally, an extra 2-pin header is provided with another VCC and GND pin in case additional connections are required.

Reference icons are placed next to the pins used by the USART, I²C and SPI modules, and where the LED is connected, to remind you what functions those pins usually perform.

This board is supplied with two 7 pin header strips for the IO pins and one 2x3 pin for the programming connector.

ATtiny824

The ATtiny824 is one of the new AVR 2-series microcontrollers, containing xmega-style peripherals. These are more powerful and flexible than previous generations of ATmega and ATtiny chips.

This particular chip contains 8 KiB of flash and 1 KiB of RAM on an AVR CPU clocked at 20 MHz. It provides three 16bit PWM-capable timers, a 16bit realtime counter, two USARTs with fractional baud rate generator, a master/slave capable SPI interface, I²C interface, analog comparator, 12bit differential ADC with PGA, and in total 12 IO pins split across two ports. It also provides a 6-channel event system and configurable custom logic block that can route events between peripherals without waking the CPU.

Compared to the ATtiny814, this chip has twice the SRAM, adds a second TCB unit, a second USART unit, and fixes some bugs and missing features with the design of the TCB. It does remove the 12-bit dual output TCD timer and DAC output, though.

More information can be found on Microchip's website at https://www.microchip.com/wwwproducts/en/ATTINY824

Why did you make it?

I wanted to experiment with the new AVR 2-series chips, but couldn't find any maker-oriented hardware for them.

What makes it special?

I believe this may be the first use of an ATtiny824, outside of the development boards produced by Microchip themselves.

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