STC8G1K08-38I-TSSOP20 from STC Micro, in a TSSOP-20. 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	P1.2/ADC2/SS/T2/ECI	bidirectional	General-purpose I/O P1.2. Muxed alt-functions: ADC channel 2 (analog input), SPI slave-select SS (I/O), Timer 2 external clock input (T2), and PCA external pulse input (ECI). Post-reset state: high-impedance input.
2	P1.3/ADC3/T2CLKO/MOSI	bidirectional	General-purpose I/O P1.3. Muxed alt-functions: ADC channel 3, Timer 2 clock-divider output (T2CLKO), and SPI master-out/slave-in (MOSI, I/O).
3	P1.4/ADC4/MISO/SDA	bidirectional	General-purpose I/O P1.4. Muxed alt-functions: ADC channel 4, SPI master-in/slave-out (MISO, I/O), and I2C data line (SDA, I/O, open-drain when used as I2C).
4	P1.5/ADC5/SCLK/SCL	bidirectional	General-purpose I/O P1.5. Muxed alt-functions: ADC channel 5, SPI clock (SCLK, I/O), and I2C clock line (SCL, I/O).
5	P1.6/ADC6/RxD_3/MCLKO_2/XTALO	bidirectional	General-purpose I/O P1.6. Muxed alt-functions: ADC channel 6, UART1 RxD alternate mapping 3, master-clock divider output (MCLKO_2), and external crystal output (XTALO) when using an external HSE crystal.
6	P1.7/ADC7/TxD_3/XTALI	bidirectional	General-purpose I/O P1.7. Muxed alt-functions: ADC channel 7, UART1 TxD alternate mapping 3, and external crystal input (XTALI) when using an external HSE crystal.
7	P5.4/NRST/MCLKO	bidirectional	General-purpose I/O P5.4. Alt-functions: active-low external reset input (NRST, low-level reset) when configured as reset pin, or master-clock divider output (MCLKO). When used as reset, the internal ~4 kΩ pull-up stays on; when used as I/O, that pull-up still enables for ~6.5 ms on power-up before auto-disable.
8	Vcc/AVcc/ADC_VRef+	power_in	Combined chip power supply (Vcc), analog ADC supply (AVcc) and ADC positive reference (ADC_VRef+). Operating supply 2.7-5.5 V typical for the STC8G family; this -38I variant is characterised over the 3.8-5.5 V industrial range. ADC_VRef+ must be tied to an external reference between 2.4 V and Vcc (floating causes leakage). Decouple with 10 µF bulk + 0.1 µF close to the pin.
9	P5.5	bidirectional	General-purpose I/O P5.5, no alt-functions on this package. Post-reset state: high-impedance input.
10	Gnd/AGnd	power_in	Combined digital and analog ground return. Digital Gnd and analog AGnd are bonded to a single package pin on TSSOP20.
11	P3.0/RxD/ADC8/INT4	bidirectional	General-purpose I/O P3.0. Muxed alt-functions: UART1 receive (RxD), ADC channel 8, and external interrupt 4 (INT4). After power-on P3.0 comes up in weak-pull-up / quasi-bidirectional mode (unlike other pins).
12	P3.1/TxD/ADC9	bidirectional	General-purpose I/O P3.1. Muxed alt-functions: UART1 transmit (TxD, output) and ADC channel 9. After power-on P3.1 comes up in weak-pull-up / quasi-bidirectional mode.
13	P3.2/INT0/ADC10/SCL_4/SCLK_4	bidirectional	General-purpose I/O P3.2. Muxed alt-functions: external interrupt 0 (INT0), ADC channel 10, I2C clock alternate mapping 4 (SCL_4), and SPI clock alternate mapping 4 (SCLK_4).
14	P3.3/INT1/ADC11/SDA_4/MISO_4	bidirectional	General-purpose I/O P3.3. Muxed alt-functions: external interrupt 1 (INT1), ADC channel 11, I2C data alternate mapping 4 (SDA_4), and SPI MISO alternate mapping 4 (MISO_4).
15	P3.4/T0/T1CLKO/ADC12/ECI_2/CMPO/MOSI_4	bidirectional	General-purpose I/O P3.4. Muxed alt-functions: Timer 0 external clock input (T0), Timer 1 clock-divider output (T1CLKO), ADC channel 12, PCA external pulse input alternate 2 (ECI_2), comparator output (CMPO), and SPI MOSI alternate mapping 4 (MOSI_4).
16	P3.5/T1/T0CLKO/ADC13/CCP0_2/SS_4	bidirectional	General-purpose I/O P3.5. Muxed alt-functions: Timer 1 external clock input (T1), Timer 0 clock-divider output (T0CLKO), ADC channel 13, PCA CCP0 capture/compare/PWM alternate mapping 2 (CCP0_2), and SPI slave-select alternate mapping 4 (SS_4).
17	P3.6/INT2/RxD_2/ADC14/CCP1_2/CMP-	bidirectional	General-purpose I/O P3.6. Muxed alt-functions: external interrupt 2 (INT2), UART1 RxD alternate mapping 2, ADC channel 14, PCA CCP1 alternate mapping 2 (CCP1_2), and comparator negative input (CMP-).
18	P3.7/INT3/TxD_2/CCP2/CCP2_2/CMP+	bidirectional	General-purpose I/O P3.7. Muxed alt-functions: external interrupt 3 (INT3), UART1 TxD alternate mapping 2, PCA CCP2 capture/compare/PWM (default and alternate 2 mappings), and comparator positive input (CMP+). Also serves as internal ADC15 reference tap (1.19 V bandgap) when configured for internal-reference measurements.
19	P1.0/RxD2/ADC0/CCP1	bidirectional	General-purpose I/O P1.0. Muxed alt-functions: UART2 receive (RxD2), ADC channel 0, and PCA CCP1 capture/compare/PWM (default mapping).
20	P1.1/TxD2/ADC1/CCP0	bidirectional	General-purpose I/O P1.1. Muxed alt-functions: UART2 transmit (TxD2), ADC channel 1, and PCA CCP0 capture/compare/PWM (default mapping).

Key specifications

Parameter	Value
Manufacturer	STC Micro
Package	TSSOP-20
Category	MCU
Pins	20

Ordering variants

Same part, different packaging or reel option.

STC8G1K08-38I-TSSOP20
STC8G1K08-38I-QFN20
STC8G1K08-38I-SOP16

CAD (KiCad official)

Symbol: STC8G1K08-38I-TSSOP20
Footprint: Package_SO:TSSOP-20_4.4x6.5mm_P0.65mm
3D model: TSSOP-20 (KiCad packages3D, STEP)

3D model downloads

Two STEP files. Same geometry, different body top:

File	Size	Use it when
`stc8g1k08-38i-tssop20.step`	267 KB	You want the bare part, or you mark your own boards.
`stc8g1k08-38i-tssop20-etched.step`	5.0 MB	You want the part with `STC8G1K08-38I-TSSOP20` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 1184 faces against 327 in the bare model. It survives export, section views, and rendering in any CAD tool, and it drops straight into KiCad or Fusion with no extra setup.

Provenance

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

Datasheet: STC Micro datasheet (1240 pp, sha256 7d5e82c9f651aa92, 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