AVR128DA28T-I from Microchip Tech, in a SOIC-28-300mil. Pinout and pin descriptions extracted from the manufacturer datasheet by ds2sf; symbol, footprint, and 3D from KiCad-official CAD.

Pinout

Pin	Name	Type	Function
1	PA7	bidirectional	PORTA bit 7 GPIO. Alt: CLKOUT, PTC X7/Y7, AC0/1/2 OUT, USART0 XDIR (alt), SPI0 SS, TCD0 WOD, EVOUTA (alt).
2	PC0	bidirectional	PORTC bit 0 GPIO. Alt: USART1 TxD, SPI1 MOSI, TCA0 WO0 (alt), TCB2 WO, CCL LUT1 IN0.
3	PC1	bidirectional	PORTC bit 1 GPIO. Alt: USART1 RxD, SPI1 MISO, TCA0 WO1 (alt), TCB3 WO (alt), CCL LUT1 IN1.
4	PC2	bidirectional	PORTC bit 2 GPIO (TWI-capable pad). Alt: USART1 XCK, SPI1 SCK, TWI0 SDA(M) (alt), TCA0 WO2 (alt), EVOUTC, CCL LUT1 IN2.
5	PC3	bidirectional	PORTC bit 3 GPIO (TWI-capable pad). Alt: USART1 XDIR, SPI1 SS, TWI0 SCL(M) (alt), TCA0 WO3 (alt), CCL LUT1 OUT.
6	PD0	bidirectional	PORTD bit 0 GPIO. Alt: ADC0 AIN0, PTC X16/Y16, AC0/1/2 AINN1, TCA0 WO0 (alt), CCL LUT2 IN0.
7	PD1	bidirectional	PORTD bit 1 GPIO. Alt: ADC0 AIN1, PTC X17/Y17, ZCD0 ZCIN, TCA0 WO1 (alt), CCL LUT2 IN1.
8	PD2	bidirectional	PORTD bit 2 GPIO. Alt: ADC0 AIN2, PTC X18/Y18, AC0/1/2 AINP0, TCA0 WO2 (alt), EVOUTD, CCL LUT2 IN2.
9	PD3	bidirectional	PORTD bit 3 GPIO. Alt: ADC0 AIN3, PTC X19/Y19, AC0 AINN0, AC1 AINP1, TCA0 WO3 (alt), CCL LUT2 OUT.
10	PD4	bidirectional	PORTD bit 4 GPIO. Alt: ADC0 AIN4, PTC X20/Y20, AC1 AINP2, AC2 AINP1, TCA0 WO4 (alt).
11	PD5	bidirectional	PORTD bit 5 GPIO. Alt: ADC0 AIN5, PTC X21/Y21, AC1 AINN0, TCA0 WO5 (alt).
12	PD6	bidirectional	PORTD bit 6 GPIO. Alt: ADC0 AIN6, PTC X22/Y22, AC0/1/2 AINP3, DAC0 VOUT, TCB2 OUT (alt).
13	PD7	bidirectional	PORTD bit 7 GPIO. Alt: ADC0 VREFA (external ADC/DAC reference input), AIN7, PTC X23/Y23, AC0/1 AINN2, AC2 AINN0/AINN2, EVOUTD (alt).
14	AVDD	power_in	Analog supply pin, 1.8-5.5 V. Internally connected to VDD on this family, but must be decoupled locally with its own capacitor pair to GND.
15	GND	power_in	Analog/digital ground return (paired with AVDD). Tie to system ground plane.
16	PF0/XTAL32K1	bidirectional	PORTF bit 0 GPIO / 32.768 kHz crystal input XTAL32K1. Alt: ADC0 AIN16 (positive-input only), PTC X32/Y32, USART2 TxD, TCA0 WO0 (alt), TCD0 WOA (alt), CCL LUT3 IN0.
17	PF1/XTAL32K2	bidirectional	PORTF bit 1 GPIO / 32.768 kHz crystal output XTAL32K2. Alt: ADC0 AIN17 (positive-input only), PTC X33/Y33, USART2 RxD, TCA0 WO1 (alt), TCD0 WOB (alt), CCL LUT3 IN1.
18	PF6/RESET	input	External Reset input (active-low), input-only pin. Configurable as GPIO PF6 (input-only) in RSTCTRL. Pull to VDD with a resistor when used as RESET.
19	UPDI	bidirectional	Unified Program and Debug Interface - single-wire programming/debug pin. Requires 4.7-10 kΩ pull-up to VDD in typical designs.
20	VDD	power_in	Digital supply pin, 1.8-5.5 V. Decouple locally with 100 nF ceramic to nearby GND (pin 21).
21	GND	power_in	Digital ground return (paired with VDD). Tie to system ground plane.
22	PA0/EXTCLK	bidirectional	PORTA bit 0 GPIO / external clock input (EXTCLK) for the main clock. Alt: PTC X0/Y0, USART0 TxD, TCA0 WO0, CCL LUT0 IN0.
23	PA1	bidirectional	PORTA bit 1 GPIO. Alt: PTC X1/Y1, USART0 RxD, TCA0 WO1, CCL LUT0 IN1.
24	PA2	bidirectional	PORTA bit 2 GPIO (TWI-capable pad). Alt: PTC X2/Y2, USART0 XCK, TWI0 SDA(M) (default), TCA0 WO2, TCD0 WO, EVOUTA, CCL LUT0 IN2.
25	PA3	bidirectional	PORTA bit 3 GPIO (TWI-capable pad). Alt: PTC X3/Y3, USART0 XDIR, TWI0 SCL(M) (default), TCA0 WO3, TCA1 WO, CCL LUT0 OUT.
26	PA4	bidirectional	PORTA bit 4 GPIO. Alt: PTC X4/Y4, USART0 TxD (alt), SPI0 MOSI, TCA0 WO4, TCD0 WOA.
27	PA5	bidirectional	PORTA bit 5 GPIO. Alt: PTC X5/Y5, USART0 RxD (alt), SPI0 MISO, TCA0 WO5, TCD0 WOB.
28	PA6	bidirectional	PORTA bit 6 GPIO. Alt: PTC X6/Y6, USART0 XCK (alt), SPI0 SCK, TCD0 WOC, CCL LUT0 OUT (alt).

Key specifications

Parameter	Value
Manufacturer	Microchip Tech
Package	SOIC-28-300mil
Category	Embedded Processors & Controllers
Pins	28

Ordering variants

Same part, different packaging or reel option.

AVR128DA28T-II/SO
AVR128DA28T-IE/SO
AVR128DA28T-II/SS
AVR128DA28T-IE/SS
AVR128DA28T-II/SP
AVR128DA28T-IE/SP
AVR128DA28T-II/RXB
AVR128DA28T-II/PT
AVR128DA28T-IE/RXB
AVR128DA28T-IE/PT
AVR128DA28T-II/6LX
AVR128DA28T-IE/6LX
AVR128DA28T-II/MR
AVR128DA28T-IE/MR

CAD (KiCad official)

Symbol: AVR128DA28T-I
Footprint: Package_SO:SOIC-28W_7.5x17.9mm_P1.27mm
3D model: SOIC-28-300mil (KiCad packages3D, STEP)

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

Datasheet: Microchip Tech datasheet (None pp, sha256 4623d54c2494b8fd, retrieved 2026-08-17, tier: lcsc)
Extractor: ds2sf (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF