¶ Airedale - FluidNC I/O Expander
¶ Overview
This device adds additional I/O pins to a FluidNC controller via a UART connection. It has inputs that can be used for switches. It also has outputs that can be digital or PWM.
Note: The hardware and firmware are in beta testing and still experimental. There may be bugs in the firmware and hardware. You may need to upgrade firmware. Please do not purchase this if you need a device with proven field reliability.
¶ Features
- (8) Inputs
- (8) 5V outputs (digital or PWM)
- (2) MOSFETs (digital or PWM)
- LED indicators on all inputs and outputs.
- (1) UART Pass through
- RGB status indicator
- ST-Link programming port
¶ UART Pass through
This features allows you to add another UART channel device like a pendant or display. The expander filters out expander specific communication and sends the rest out the pass through port. All data received on the pass through is sent through the other UART to the FluidNC controller.
¶ Pin Numbers
The pins are labeled with a number. This is the number you use in the config file. You specify the UART channel number and the pin number like:
safety_door_pin: uart_channel2.0:low
Note: This number has nothing to do with the STM32 pin numbers or the ESP32 GPIO numbers.
¶ Inputs
All inputs go through opto isolators. You connect the input to ground to activate the input. They all have pull up resistor on the PCB. They are all active low. There are some 5V terminals you can use with powered switches.
An LED associated with each input that lights when the circuit is activated.
example
control:
safety_door_pin: uart_channel2.0:low
Note: Type typical response time is several milliseconds. You might want to put things like limit switches and probe pins on ESP32 gpio if you are looking for the highest response time.
¶ Outputs
The 5V outputs all go through 74AHCT125 buffers. They can each source and sink 25mA, but the total for each group of 4 is 50mA total.
The outputs cannot be used for motion control (stepper pins) or other very high speed, tightly coordinated control, like laser engraver power level.
¶ PWM Limitations
The STM32 uses (4) timers for generating PWM frequencies. You can use any output pin for PWM, but you can only have (4) different frequencies.
The timers are wired to specific pins inside the STM32. All pins that share a timer must be on the same frequency. The controller is labeled with the pin numbers and the associated timer number. For example: the label 8 (T1) means this is pin 8 and uses timer 1. All pins with the same timer number must use the same frequency or your config will will give an alarm and load a default config.
¶ MOSFETs
The MOSFETs (HYG017N04LS1C2) are rated for 40V and lots of current. The max current is determined by the terminal block which is rated at 8A per terminal.
The 2 terminals near the RJ12 connector are for the power input. The ground is common with common with the rest of the PCB.
¶ RJ12 UART Connections
The expander is designed to connect to the FluidNC controller using the standard RJ12 we use for pendants and displays. There is a module for this for controllers that support CNC I/O modules.
Controllers without an RJ12 option can be wired to the header next to the RJ12 connector. Be very careful with the wiring any mis-wire or electrical spikes will damage the expander and your FluidNC controller. The RJ12 modules have some protective circuitry. The Vm pin is only wired to the other RJ12 connector and can be used to power the attached display or pendant.
¶ RGB Status indicator
There is an RGB LED located near the pendant RJ12 connector. This is used to give basic operational status of the Airedale.
This feature has not been implemented yet.
¶ Config file
You need to create a UART. The ESP32 has three (0, 1 & 2). The standard USB/Serial port uses 0, so you must use 1 or 2.
The baud for the extender is 1000000
The passthrough_baud should be 57600. In this case the passthrough is referring to passing data from the primary FluidNC serial port to the UART being defined. This is used when uploading firmware from FluidTerm.
If you are using a display or pendant on the second UART, you should have a report interval other than 0.
uart2:
txd_pin: gpio.25
rxd_pin: gpio.27
baud: 1000000
mode: 8N1
passthrough_baud: 57600
passthrough_mode: 8E1
uart_channel2:
report_interval_ms: 75
uart_num: 2
The I/O pins are assigned like this.
¶ Loading/Upgrading Firmware
There are 2 ways to do this.
¶ Via FluidTerm and the UART
Enter bootload mode by holding down the Boot button, clicking the reset button, then releasing the boot button. It will stay in boot mode until you click the reset button, so be sure to click the reset or power cycle after programming to exit bootloader mode.
¶ ST-Link Header
You need a programmer. The ST-Link V2 can be purchased for about $6 on Amazon.
There is an ST-Link header connector on the Airedale. It ls located below the boot and reset buttons. Use the STM32 ST-Link Utility program. Connect the ST-Link as follows
ST-Link | Airdale
3.3V | 3v3
GND | Gnd
SWDIO | SWD
SWCLK | SWC
¶ Source Files
¶ Pinout
¶ Errata (known issues)
¶ V1.1
- All single color LEDs are red. They will be green in production
- Output #14 is not functional. The connection to the CPU is missing.