10 years ago.

Choosing the Best board.


I'm working on a project to recreate the DSKY. (http://www.ibiblio.org/apollo/ArtistDSKY.jpg) It would requires around 32 IO pins (Possibly more). I wanted to get away from the Arduino platform (Reason aside) which board would be the best that is compatible for mbed?

The requirements would be: Minimum of 32 GPIO pins. Contains RTC Ethernet is not a requirement, but would be a plus to communicate with other systems Can be brought within the US.

The board that looks promising is the LPC4088 but unfortunately it's in the UK (102USD). The other board that seems to suit the requirements is the free scale board but I don't know exactly how many GPIO pins are on it.

Sorry for my newness. I wanted to dive into embedded systems knee deep. Coming from the IT industry, going into engineering program.

Are you interested with boards or are you going to assemble your own?

The ethernet fulfills LPC1768 (the mbed board). The pinout says there are 40 headers, so you might get around 30 gpio pins. The Freescale Freedom boards (KL25Z, KL46Z) have more than 32 gpio available on on-board headers, but no ethernet peripheral. A ethernet module can be connected through SPI for example, if needed.

The target LPC4088 has exactly 32 gpio pins available. However, not certain if any of those 32 pins does not have any functionality which might not be changed to gpio. Like usb or that pushbutton on P23. So even with this board, you might get less than 32 gpio pins. I would recommend checking platforms page where are pictures with all pins available.


posted by Martin Kojtal 02 Feb 2014

LPC4088s are available at Mouser.com. I just got one for $70.

Wup, just checked and they sold out. More due in 2/14

posted by Dan D. 03 Feb 2014

2 Answers

10 years ago.

A device like DSKY doesn't really need that many gpio pins. The update or scanrates for keys and displays are relatively slow. You can easily use a couple of portexpanders that convert between a serial protocol like I2C or SPI and your keys or display. That saves a lot of gpio pins for more useful purposes. Checkout my example code for a 4 digit starburst type LED display using simple shiftregisters and an SPI bus. It uses only 4 gpio pins to drive some 60 LEDs.

Andy Lau
10 years ago.

Eventually I will be rolling my own boards once the prototype works. For now I'm bread boarding and soon will have to start wire wrapping it. My current schematic is using shift registers to drive a BCD chip so it can drive the 7 segment displays (Makes a large reduction in pins). The keypad is a 4x4 matrix and adding 3 additional button. As for the indicator lights I haven't figured out how to drive it. Chances are it's going to also use shift registers. My long term goal if this works, is to have a community underneath and make an attempt to make a 1:1 scale of the Command module cockpit down to the buttons, sensors, and displays.

I want to find a platform that I can use consistently across the project. That way I don't get any incompatibility or having to change platform to which I program from one another.