LPC1769 Pin Usage

This page documents all pin assignments for the LPC1769 microcontroller on Smoothieboard.

This comprehensive reference shows how every pin on the LPC1769 is assigned on Smoothieboard. Use this to identify available pins for custom functionality.

Pin list

The following table shows all pin assignments on the LPC1769 microcontroller:

ARM Pin Smoothie Pin mBed Pin LPCXpresso Pin Assignment Comment
P0.0 0.0 P9 9 i2c1 sda Internal I2C bus. Used for digipots and port expander.
P0.1 0.1 P10 10 i2c1 scl Internal I2C bus. Used for digipots and port expander.
P0.2 0.2 USBTX 21 uart0 txd Used for ISP programming of the bootloader and for debugging.
P0.3 0.3 USBRX 22 uart0 rxd Used for ISP programming of the bootloader and for debugging.
P0.4 0.4 P30 38 alpha_en_pin  
P0.5 0.5 P29 39 alpha_dir_pin  
P0.6 0.6 P8 8 spi1 ssel sdcard
P0.7 0.7 P7 7 spi1 sck sdcard
P0.8 0.8 P6 6 spi1 miso sdcard
P0.9 0.9 P5 5 spi1 mosi sdcard
P0.10 0.10 P28 40 beta_en_pin also i2c2 sda
P0.11 0.11 P27 41 beta_dir_pin also i2c2 scl
P0.15 0.15 P13 13 spi0 sck User spi port. used for rrd glcd
P0.16 0.16 P14 14 spi0 ssel User spi port. used for rrd glcd cs
P0.17 0.17 P12 12 spi0 miso User spi port.
P0.18 0.18 P11 11 spi0 mosi User spi port. used for rrd glcd
P0.19 0.19 - Pad17 gamma_en_pin also i2c3 sda on lpcxpresso e2prom
P0.20 0.20 - Pad18 gamma_dir_pin also i2c3 scl on lpcxpresso e2prom
P0.21 0.21 - 23 delta_en_pin  
P0.22 0.22 - 24 delta_dir_pin lpcxpresso led
P0.23 0.23 P15 15 hotend.thermistor_pin  
P0.24 0.24 P16 16 bed.thermistor_pin  
P0.25 0.25 P17 17 thermistor2  
P0.26 0.26 P18 18 thermistor3  
P0.27 0.27 - 25 i2c0 sda User i2c port. sd cd on rrd glcd adapter
P0.28 0.28 - 26 i2c0 scl User i2c port. sd cs2 on rrd glcd adapter
P0.29 0.29 31 37 USB-D+  
P0.30 0.30 32 36 USB-D-  
P1.0 1.0     eth txd0  
P1.1 1.1     eth txd1  
P1.4 1.4     eth tx en  
P1.8 1.8     eth crs  
P1.9 1.9     eth rxd0  
P1.10 1.10     eth rxd1  
P1.14 1.14     eth rx err  
P1.15 1.15     eth ref clk  
P1.16 1.16     eth mdc  
P1.17 1.17     eth mdio  
P1.18 1.18 LED1 Pad1 led1 h/w PWM capable. can be free if leds_disable is set true in config.
P1.19 1.19 - Pad2 led2 can be free if leds_disable is set true in config.
P1.20 1.20 LED2 Pad3 led3 h/w PWM capable. can be free if leds_disable is set true in config.
P1.21 1.21 LED3 Pad4 led4 h/w PWM capable. can be free if leds_disable is set true in config.
P1.22 1.22 - Pad5 3rd small fet spare on 3 and 4 driver boards
P1.23 1.23 LED4 Pad6 3rd large fet spare on 3 and 4 driver boards, h/w PWM capable
P1.24 1.24 - Pad7 alpha_min_endstop h/w PWM capable
P1.25 1.25 - Pad8 alpha_max_endstop  
P1.26 1.26 - Pad9 beta_min_endstop h/w PWM capable
P1.27 1.27 - Pad10 beta_max_endstop  
P1.28 1.28 - Pad11 gamma_min_endstop  
P1.29 1.29 - Pad12 gamma_max_endstop  
P1.30 1.30 P19 19 spare used for click button on rrd glcd
P1.31 1.31 P20 20 spare used for buzzer on rrd glcd
P2.0 2.0 P26 42 alpha_step_pin h/w PWM capable
P2.1 2.1 P25 43 beta_step_pin h/w PWM capable
P2.2 2.2 P24 44 gamma_step_pin h/w PWM capable
P2.3 2.3 P23 45 delta_step_pin h/w PWM capable
P2.4 2.4 P22 46 psu.output_pin h/w PWM capable
P2.5 2.5 P21 47 bed.heater_pin h/w PWM capable
P2.6 2.6 - 48 fan.output_pin  
P2.7 2.7 - 49 hotend.heater_pin  
P2.8 2.8 - 50 epsilon_step_pin spare on 3 and 4 driver
P2.9 2.9 - Pad19 USB soft connect  
P2.10 2.10 - 51 ISP button  
P2.11 2.11 - 52 spare used for pause/kill/back pin on glcd
P2.12 2.12 - 53 kill button Hardwired in Bootloader as ISP button and in kill module as pause button
P2.13 2.13 - 27 epsilon_dir_pin spare on 3 and 4 driver
P3.25 3.25 - Pad13 spare used for encoder pin for all panels, h/w PWM capable
P3.26 3.26 - Pad14 spare used for encoder pin for all panels, h/w PWM capable
P4.28 4.28 - Pad15 play/pause led  
P4.29 4.29 - Pad16 epsilon_en_pin spare on 3 and 4 driver cannot be used in opendrain
Hardwired Pins:

The following pins are hardwired and would need to be changed in source code: 0.2 0.3, 0.6-0.9, 0.29, 0.30, 2.9, 2.10, 2.12. The rest are configurable in config.

Some pins are also setup as outputs and changed in the Bootloader and those are not configurable, these pins are: 1.18, 1.19, 1.20, 1.21, 4.28, 2.4, 2.5, 2.6, 2.7. However once booted these can be reassigned if needed.

P0.* and P2.* can be setup as interrupt enabled pins.

The LPC1769 pin list does not apply to V2 Prime. See STM32H7 pin usage.

Pin Format Reference

V1 Pin Format: port.pin with optional modifiers

  • Basic format: 1.24, 2.0, 0.11
  • Pull-up modifier: 1.24^ (enable internal pull-up)
  • Inverted logic: 1.24! (invert pin logic)
  • Open-drain: 2.0o (configure as open-drain)
  • Combined: 1.24^! (pull-up + inverted)

V2 Pin Format: Similar port.pin format with additional options

  • Basic format: PA.0, PB.5, or numeric 1.24, 2.0
  • Named pins: Board-specific named pins may be available
  • Modifiers: Similar to V1 (pull-up ^, inverted !, open-drain o)
  • Check board-specific documentation for exact pin names and available features

Migration Guide: V1 to V2 Pin Configuration

This section shows real-world examples of converting V1 pin configurations to V2 format.

Stepper Motor Pin Configuration

# Alpha (X) axis motor configuration
alpha_step_pin                      2.0
alpha_dir_pin                       0.5
alpha_en_pin                        0.4

# Beta (Y) axis motor configuration
beta_step_pin                       2.1
beta_dir_pin                        0.11
beta_en_pin                         0.10

# Alpha (X) axis motor configuration
alpha_step_pin                      2.0
alpha_dir_pin                       0.5
alpha_en_pin                        0.4

# Beta (Y) axis motor configuration
beta_step_pin                       2.1
beta_dir_pin                        0.11
beta_en_pin                         0.10

# V2 maintains backward compatibility with numeric pin format
# Named pin aliases may be available depending on board

Endstop Configuration with Modifiers

# Min endstops with pull-up resistors
alpha_min_endstop                   1.24^
beta_min_endstop                    1.26^
gamma_min_endstop                   1.28^

# Max endstops inverted logic
alpha_max_endstop                   1.25!
beta_max_endstop                    1.27!
gamma_max_endstop                   1.29!

# Min endstops with pull-up resistors
alpha_min_endstop                   1.24^
beta_min_endstop                    1.26^
gamma_min_endstop                   1.28^

# Max endstops inverted logic
alpha_max_endstop                   1.25!
beta_max_endstop                    1.27!
gamma_max_endstop                   1.29!

# Modifier syntax remains the same in V2

Heater and Temperature Sensor Configuration

# Hotend configuration
temperature_control.hotend.heater_pin    2.7
temperature_control.hotend.thermistor_pin 0.23

# Heated bed configuration
temperature_control.bed.heater_pin       2.5
temperature_control.bed.thermistor_pin   0.24

# Hotend configuration
temperature_control.hotend.heater_pin    2.7
temperature_control.hotend.thermistor_pin 0.23

# Heated bed configuration
temperature_control.bed.heater_pin       2.5
temperature_control.bed.thermistor_pin   0.24

# Pin assignments remain compatible in V2

Fan and Switch Configuration

# Cooling fan
switch.fan.output_pin               2.6

# PSU control (inverted, open-drain)
switch.psu.output_pin               2.4!o

# Auxiliary outputs
switch.misc.output_pin              1.22

# Cooling fan
switch.fan.output_pin               2.6

# PSU control (inverted, open-drain)
switch.psu.output_pin               2.4!o

# Auxiliary outputs
switch.misc.output_pin              1.22

# Modifier combinations (!o) work the same in V2

Pin Format Comparison Table

The following table shows common pin assignments with V1 and V2 format side-by-side:

Function V1 Pin Format Notes
Alpha Step 2.0 Basic numeric format
Alpha Dir 0.5 Port.pin notation
Alpha Enable 0.4 Standard output
Alpha Min Endstop 1.24^ With pull-up
Alpha Max Endstop 1.25! Inverted logic
Hotend Heater 2.7 PWM capable
Hotend Thermistor 0.23 ADC input
Bed Heater 2.5 PWM capable
Bed Thermistor 0.24 ADC input
Fan Output 2.6 Standard output
PSU Control 2.4!o Inverted + open-drain
Spare I/O 1.30^ With pull-up
LED 1.18 PWM capable
Function V2 Pin Format Notes
Alpha Step 2.0 or PA.0 Numeric or named format
Alpha Dir 0.5 or PA.5 Board-dependent naming
Alpha Enable 0.4 or PA.4 Check board docs
Alpha Min Endstop 1.24^ Modifier syntax same
Alpha Max Endstop 1.25! Inverted logic same
Hotend Heater 2.7 PWM capable
Hotend Thermistor 0.23 ADC input
Bed Heater 2.5 PWM capable
Bed Thermistor 0.24 ADC input
Fan Output 2.6 Standard output
PSU Control 2.4!o Modifiers work same
Spare I/O 1.30^ Pull-up syntax same
LED 1.18 PWM capable

LPC176x ADC channels and pins

Adc Channel Port Pin Pin Functions Associated PINSEL Register
AD0 P0.23 0-GPIO, 1-AD0[0], 2-I2SRX_CLK, 3-CAP3[0] 14,15 bits of PINSEL1
AD1 P0.24 0-GPIO, 1-AD0[1], 2-I2SRX_WS, 3-CAP3[1] 16,17 bits of PINSEL1
AD2 P0.25 0-GPIO, 1-AD0[2], 2-I2SRX_SDA, 3-TXD3 18,19 bits of PINSEL1
AD3 P0.26 0-GPIO, 1-AD0[3], 2-AOUT, 3-RXD3 20,21 bits of PINSEL1
AD4 P1.30 0-GPIO, 1-VBUS, 2- , 3-AD0[4] 28,29 bits of PINSEL3
AD5 P1.31 0-GPIO, 1-SCK1, 2- , 3-AD0[5] 30,31 bits of PINSEL3
AD6 P0.3 0-GPIO, 1-RXD0, 2-AD0[6], 3- 6,7 bits of PINSEL0 * not available on Smoothieboard
AD7 P0.2 0-GPIO, 1-TXD0, 2-AD0[7], 3- 4,5 bits of PINSEL0 * not available on Smoothieboard
ADC pins are not 5v tolerant.

V2 Prime uses the STM32H745 ADC mapping; see STM32H7 pin usage.

Pinout

Pinout

This page shows the pinout diagrams for the board.

Wiring Diagram

Click the images below to view them at full size.
Smoothieboard Wiring

Smoothieboard wiring diagram - click to enlarge

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Pin Capabilities

Smoothieboard Pin Capabilities

Smoothieboard pin capabilities - click to enlarge

View full size pin capabilities diagram

Also see the pin usage table for detailed information about each pin.

 Work in Progress
The V2 pinout diagrams are still being created. Check back soon for updated wiring and pin capability diagrams for V2 boards.

Important Notes

Do not use endstop inputs as outputs (for example to control a solid state relay), this will not work.

See STM32H7 pin usage for V2 Prime pin assignments.
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