The following documents the hardware inside the Radiolink AT9 transmitter

STM32 Connections

Pin Connection Description Additional Info
BOOT0 BOOT0

GPIOA

Pin Connection Description Additional Info
PA00 CH1 SRH RIght Hor Stick
PA01 CH2 SLV Left Ver Stick
PA02 CH3 SRV Right Ver Stick
PA03 CH4 SLH Left Hor Stick
PA04 POT Right Shoulder VRE
PA05 POT Left Front Dial VRA
PA06 POT Right Front Dial VRB
PA07 POT Center Front Dial VRC
PA09 TX Boot connector
PA10 RX Boot connector
PA11 BUZZ Buzzer
PA13 LED Green To cathode through limiting resistor
PA14 ENTER Menu button 1K resistor to GND
PA15 EXIT Menu button 1K resistor to GND

GPIOB

Pin Connection Description Additional Info
PB00 POT Left Shoulder VRD
PB01 LOWBAT Battery Voltage
PB03 TRL Right Trim Left
PB04 TRR Right Trim Right
PB05 TLU Left Trim Up
PB06 TLD Left Trim Down
PB07 PC OUT PCM port 4.7K limiting resistor
PB08 PC IN PCM port 4.7K limiting resistor
PB09 DISP24 PWM for LEDs Transistor to GND
PB11 REST RF board
PB12 CSN RF board
PB13 SCK RF board
PB14 MISO RF board
PB15 MOSI RF board

GPIOC

Pin Connection Description Additional Info
PC00 K1A 2-pos switch
PC01 K2B 2-pos switch
PC02 K3C1 3-pos switch
PC03 K3C2 3-pos switch
PC04 K5E1 3-pos switch
PC05 K5E2 3-pos switch
PC06 K4D 2-pos switch RC filter
PC07 K6F 2-pos switch RC filter
PC08 K7G 2-pos switch RC filter
PC09 K8H 2-pos switch RC filter
PC10 SDA EEPROM
PC11 SCL EEPROM
PC12 LED RED To cathode through limiting resistor
PC13 ENC L Rotary Encoder 10K pull-up
PC14 ENC R Rotary Encoder 10K pull-up
PC15 ENC Button Rotary Encoder Direct to pin

GPIOD

Pin Connection Description Additional Info
PD00 DISP5 Data
PD01 DISP6 Data
PD02 TRU Right Trim Up
PD03 TRD Right Trim Down
PD04 DISP21 Control
PD05 DISP22 Control
PD06 USB DETECT Detect USB Plugin
PD07 DISP20 Control
PD08 DISP16 Data
PD09 DISP17 Data
PD10 DISP18 Data
PD11 DISP23 Control
PD12 TLL Left Trim to Left
PD13 TLR Left Trim to Right
PD14 DISP3 Data
PD15 DISP4 Data

GPIOE

Pin Connection Description Additional Info
PE00 DISP19 RESx ILI9341 Pin Reset is Active low
PE01 POINT1
PE02 POINT2
PE03 POINT3
PE04 POINT4
PE05 POINT6
PE06 POINT10
PE07 DISP7 Data
PE08 DISP8 Data
PE09 DISP9 Data
PE10 DISP10 Data
PE11 DISP11 Data
PE12 DISP12 Data
PE13 DISP13 Data
PE14 DISP14 Data
PE15 DISP15 Data

Battery Voltage Measurement

The battery voltage (ADC1_9) was measured as:

Voltage ADC Value
15.05V 0x0FFB
10.02V 0x0A9D
4.31V 0x048E

is calculated by the formula: V = 0.003672 * value + 0.0287

FCC Report

FCCID: U2B RL039AT10

Schematic is available here (courtesy of FCC): at10_schematics.pdf