Re-ARM
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Release status: Working
| Description | 32-bit NXP LPC1768 (ARM Cortex-M3) drop-in replacement for the Arduino Mega2560 in a RAMPS 1.4 setup
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Contents
Summary
The Re-ARM is a 32-bit controller board made by Panucatt Devices. It has the same shape and header layout (Arduino "R3" form factor) as an Arduino Mega2560, so it plugs straight into a RAMPS 1.4 shield in place of the Mega. This upgrades an existing RAMPS printer to a 32-bit processor without rewiring the steppers, endstops, heaters or thermistors.
| Feature | Re-ARM | Arduino Mega2560 (for comparison) |
|---|---|---|
| Processor | NXP LPC1768, ARM Cortex-M3, 100 MHz | ATmega2560, 8-bit AVR, 16 MHz |
| Flash | 512 KB | 256 KB |
| RAM | 64 KB | 8 KB |
| Logic level | 3.3 V (most digital pins are 5 V tolerant, see Special pins) | 5 V |
| Analog inputs | 8 (0–3.3 V) | 16 (0–5 V) |
| Hardware PWM channels | 6 | 15 |
| Firmware storage | On-board microSD card | Internal flash (via bootloader) |
Firmware
Marlin
Re-ARM is supported in Marlin 2.0 and later. It is built with PlatformIO, not the Arduino IDE.
- In
Configuration.hsetMOTHERBOARDto the Re-ARM variant that matches your RAMPS outputs, for example:-
BOARD_RAMPS_14_RE_ARM_EFB– Extruder, Fan, Bed (the usual single-extruder setup) -
BOARD_RAMPS_14_RE_ARM_EEB– Extruder, Extruder, Bed -
BOARD_RAMPS_14_RE_ARM_EFF– Extruder, Fan, Fan -
BOARD_RAMPS_14_RE_ARM_EEF– Extruder, Extruder, Fan -
BOARD_RAMPS_14_RE_ARM_SF– Spindle/laser, Fan
-
- Build the
LPC1768PlatformIO environment. This producesfirmware.bin. - Copy
firmware.binto the root of the Re-ARM's microSD card and press reset (or power-cycle). The bootloader flashes the file and renames it toFIRMWARE.CUR.
While Marlin is running, the microSD card also shows up on the host PC as a USB drive, so new firmware can be copied over USB without removing the card.
The pin definitions are in Marlin/src/pins/lpc1768/pins_RAMPS_RE_ARM.h. The pin numbers used on this page are the Marlin logical ("Arduino style") pin numbers.
Smoothieware
See the Panucatt quick start guide.
Compatible shields
- RAMPS 1.4 – the only known compatible shield.
- RAMPS-FD – does not fit; it has a mechanical interference problem with the Re-ARM.
Pinout when used with RAMPS 1.4
The LPC1768 has fewer I/O pins than the Mega2560. As a result some Mega2560 logical pins are not available on the Re-ARM, and some logical pins appear on two different physical pins.
The logical pin numbers in the pictures below are Marlin pin numbers.
The following Mega2560 logical pins are not available on a Re-ARM:
D7, D17, D22, D23, D25, D27, D29, D32, D39, D40, D42, D43, D44, D45, D47, D64, D65, D66
If your configuration or an add-on board uses one of these pins, pick a different pin.
Special pins
| Pin | Limitation |
|---|---|
| D37 | Not 5 V tolerant |
| D49 | Not 5 V tolerant |
| D57 | Open collector output |
| D58 | Open collector output |
PWM
There are 6 hardware PWM outputs. They do not share resources with the rest of the system, so all 6 are available.
SERVO2 does not have a PWM assigned to it.
Analog inputs
The Re-ARM has 8 analog inputs, compared with 16 on the Mega2560.
| Analog input | Logical pin | Marlin use |
|---|---|---|
| A0 (T0) | D67 | TEMP_0_PIN |
| A1 (T1) | D68 | TEMP_BED_PIN |
| A2 (T2) | D69 | TEMP_1_PIN |
| A3 | D63 | |
| A4 | D37 | BUZZER_PIN |
| A5 | D49 | SD_DETECT_PIN |
| A6 | D0 | RXD0 |
| A7 | D1 | TXD0 |
Notes:
- D63, D67, D68 and D69 still have analog inputs assigned to them.
- D67, D68 and D69 are the only analog inputs that work without external signal conditioning. All the others have large noise spikes (25% or more).
- When used as analog inputs the pins are NOT 5 V tolerant. The usable range is 0–3.3 V.
Thermistor inputs: J7, J9 & J10
The three thermistor inputs (D67, D68 and D69) can come either from the RAMPS board or from the thermistor connectors on the Re-ARM itself. The inputs on the Re-ARM have less noise.
Solder jumpers J7, J9 and J10 on the Re-ARM select which set is active. The board ships with the RAMPS thermistor inputs enabled. See the J7/J9/J10 pictures in the gallery above.
LCDs
Most LCDs connect to the J3 and J5 connectors on the Re-ARM board. J3 is pinned out for the 12-pin Viki2 LCD flat ribbon cable.
The standard Smart LCD adapter can be used with RepRapDiscount Full Graphic Smart Controller type displays, but the pinout is different from when it is used with a Mega2560:
- If your LCD needs +5 V you will need a special EXP1 cable.
- If your LCD uses any of these signals you must use J3 and J5:
- LCD_PINS_D5, LCD_PINS_D6 and LCD_PINS_D7
- DOGLCD_A0 and DOGLCD_CS
- Starting with MKS, many LCD displays have the shrouds on the EXP1 and EXP2 connectors rotated 180 degrees compared with the RepRapDiscount display. To use the Smart LCD adapter with these you need either a custom cable, or to carefully pry up and reverse the connector shrouds on the adapter (preferred) or on the display.
Note: The Mega2560 pinout uses two SPI channels, but the Re-ARM only routes one to the LCD adapter. This causes garbage or lines on the RepRapDiscount Full Graphic display when the SD card is accessed, and sometimes the garbage stays on the "Print from SD" menu after the SD card access has finished. Marlin 2.0 (from late 2017) includes a software workaround for this.
Schematic
Cross reference: Marlin logical pin and LPC1768 port pin
Click a column header to sort by logical pin or by port pin.
| Marlin logical pin | LPC1768 port.pin | Notes |
|---|---|---|
| D0 | P0_03 | A6 (analog), RXD0 |
| D1 | P0_02 | A7 (analog), TXD0 |
| D2 | P1_25 | |
| D3 | P1_24 | |
| D4 | P1_18 | |
| D5 | P1_19 | |
| D6 | P1_21 | |
| D8 | P2_07 | |
| D9 | P2_04 | |
| D10 | P2_05 | |
| D11 | P1_20 | |
| D12 | P2_12 | |
| D13 | P4_28 | |
| D14 | P1_26 | |
| D15 | P1_27 | |
| D16 | P0_16 | |
| D18 | P1_29 | |
| D19 | P1_28 | |
| D20 | P0_00 | |
| D21 | P0_01 | |
| D24 | P0_04 | |
| D26 | P2_00 | |
| D28 | P0_05 | |
| D30 | P4_29 | |
| D31 | P3_26 | |
| D33 | P3_25 | |
| D34 | P2_13 | |
| D35 | P2_11 | |
| D36 | P2_08 | |
| D37 | P1_30 | A4 (analog), BUZZER_PIN, not 5V tolerant |
| D38 | P0_10 | |
| D41 | P1_22 | |
| D46 | P2_03 | |
| D48 | P0_22 | |
| D49 | P1_31 | A5 (analog), SD_DETECT_PIN, not 5V tolerant |
| D50 | P0_17 | |
| D51 | P0_18 | |
| D52 | P0_15 | |
| D53 | P1_23 | |
| D54 | P2_01 | |
| D55 | P0_11 | |
| D56 | P0_19 | |
| D57 | P0_27 | open collector |
| D58 | P0_28 | open collector |
| D59 | P2_06 | |
| D60 | P2_02 | |
| D61 | P0_20 | |
| D62 | P0_21 | |
| D63 | P0_26 | A3 (analog) |
| D67 | P0_23 | A0 / T0, TEMP_0_PIN |
| D68 | P0_24 | A1 / T1, TEMP_BED_PIN |
| D69 | P0_25 | A2 / T2, TEMP_1_PIN |
| D70 | P1_16 | |
| D71 | P1_17 | |
| D72 | P1_15 | |
| D73 | P1_14 | |
| D74 | P1_09 | |
| D75 | P1_10 | |
| D76 | P1_08 | |
| D77 | P1_04 | |
| D78 | P1_00 | |
| D79 | P1_01 | |
| D80 | P0_06 | |
| D81 | P0_07 | |
| D82 | P0_08 | |
| D83 | P0_09 |
