My Fusilier project made some progress on hardware design choices over the holiday period. Here is what I have so far:
Processor: NXP LPC4337 ARM Cortex M4/M0 dual-core embedded controller
I have chosen this device for its abundance of on-chip functionality and dual-core CPU. I will be using the LQFP-144 package.
10/100 Ethernet: The LPC4337 provides a 10/100 Ethernet RMII interface which will be supplemented by a Microchip LAN8710A PHY and RJ-45 magnetics.
Dual High Speed USB 2.0 ports: The LPC4337 provides two High Speed USB interfaces one of which has on-chip PHY. A Microchip USB3300 PHY provides the high speed functionality for the second interface. One USB port will be dedicated to communications and support Bluetooth and WiFi dongles. The other USB port will be dedicated to Flash Drive or USB Hard Drive storage.
Buffer Memory: 32MB of SDRAM (organized as 16MBx16) will be provided for buffering purposes. This is provided to support Cloud printing and features like layer and object repeat in the printing protocol.
Touchscreen Panel: The LPC4337 provides a flexible LCD controller which will be used to drive a TFT LCD panel operating in 5:6:5 RGB mode over a 16-bit interface. A resistive touchscreen will be supported using two of the LPC4337 analogue inputs.
Stepper Motor Drivers: These will be STM dSPIN L6470 devices. The board will support 10 of these for colour printing (5), support (1) and motion axes (4). The drivers are interfaced via SPI and have on-chip motion control engines which eliminate the need for the CPU to generate step pulses.
Temperature sensing: Traditional thermistor inputs will be catered for but additionally MAXIM MAX31855 devices will be supported to facilitate Type-K thermocouples. These devices are interfaced using SPI.
I have also spent time considering the need for, and type of, buffers for translating between 3.3V and 5V (74AHCT125), filtering of end-stop and filament-out sensors (74AHCT14) and buffering of off-board signals (74AHCT245) e.g. LCD buses.
Power supply regluation is still to be done but this will likely be +24 to +5V buck conversion followed by +3.3V LDO linear regulation. I will investigate the need for a +5V supply as the L6470 motor drivers feature a +5V regulated output which could be used by the end-stop and filament-out sensors if they are passive devices and if +3.3V can be used for everything else.
More to come…