mbed road test - first impressions/what next?

The mbed serial libraries are really easy to use. mbed has four serial uart ports available; three are connected to mbed pins, and one is available through the usb connection to your pc.

The pc connection is useful for debugging. There are instructions for setting it up on Windows, Linux and the Mac. My heart sank when I saw that Windows requires a driver install, as I am running Windows 7 on a 64-bit AMD proccessor. I've had lots of driver problems in the past.

No problem with the mbed driver, though. It installed quite painlessly. My pc serial connection shows up as com6, and is working perfectly.

I'm interested in displaying graphic data from the mbed, so I took a look at the cookbook section on interfacing with Python. I'm going to explore using Python to plot data from the mbed, and I wanted to check that it's easy for a Python program to read the data that the mbed sends over the pc connection.

The cookbook explains how to set Python up for serial communication. Once you've installed the pyserial package, all you need is a short program on the mbed and a few lines of Python on the pc.

#include "mbed.h"

Serial pc(USBTX, USBRX); // tx, rx

int main() {
    pc.printf("Hello World!\n");
}

is all you need on the mbed.

On the pc, my mbed shows up on com6, so I need to tell Python to open port number 5

>>> import serial
>>> s = serial.Serial(5)
>>> line = s.readline()
>>> print line
Hello World!

>>> s.close()

The pc connection is very useful, but you may also want to interface  with other devices. A few weeks ago I purchased C328 (COMedia) JPEG  Color Camera with UART Interface. Shinichiro Nakamura has just posted an mbed library for the camera, and I couldn't resist trying it out.

A couple of days ago I got an mbed breakout board. It has an Ethernet connector, and I've been experimenting with the mbed HTTPServer. I'll report on that next.

The mbed serial libraries are really easy to use. mbed has four serial uart ports available; three are connected to mbed pins, and one is available through the usb connection to your pc.

The pc connection is useful for debugging. There are instructions for setting it up on Windows, Linux and the Mac. My heart sank when I saw that Windows requires a driver install, as I am running Windows 7 on a 64-bit AMD proccessor. I've had lots of driver problems in the past.

No problem with the mbed driver, though. It installed quite painlessly. My pc serial connection shows up as com6, and is working perfectly.

I'm interested in displaying graphic data from the mbed, so I took a look at the cookbook section on interfacing with Python. I'm going to explore using Python to plot data from the mbed, and I wanted to check that it's easy for a Python program to read the data that the mbed sends over the pc connection.

The cookbook explains how to set Python up for serial communication. Once you've installed the pyserial package, all you need is a short program on the mbed and a few lines of Python on the pc.

#include "mbed.h"

Serial pc(USBTX, USBRX); // tx, rx

int main() {
    pc.printf("Hello World!\n");
}

is all you need on the mbed.

On the pc, my mbed shows up on com6, so I need to tell Python to open port number 5

>>> import serial
>>> s = serial.Serial(5)
>>> line = s.readline()
>>> print line
Hello World!

>>> s.close()

The pc connection is very useful, but you may also want to interface  with other devices. A few weeks ago I purchased C328 (COMedia) JPEG  Color Camera with UART Interface. Shinichiro Nakamura has just posted an mbed library for the camera, and I couldn't resist trying it out.

A couple of days ago I got an mbed breakout board. It has an Ethernet connector, and I've been experimenting with the mbed HTTPServer. I'll report on that next.

Hi Romily,

Great Review on the Mbed.

I'm gonna go a little off topic and ask if you know any good references for learning Python. I here a lot of engineers use it to make guis or perform calculations and I wanted to check it out.

I'm a decent C programmer ( I use it for microcontrollers), and I thought it might be good to learn a second language.

Keep up the awesome review and thanks.

Best Regards,

Jorge Garcia

Hi Joe,

Thank for the feedback. I'm enjoying my experiments with the mbed, but I've been worried that I am posting too much. Good to know that you're getting value from the review.

I learned Python from a mixture of sources. I bought Mark Lutz's book (Learning Python) early on. It's ok but not outstanding. I learned most by trying to do stuff, Googling when I got stuck and asking friends for help. On which note - feel free to ask me if you decide to learn and have any questions. I'm romilly(dot)cocking(at)gmail(dot)com.

Python has a lot going for it - it's my favourite scripting language, and I've tried a few

Thanks Romily,

I'll let you know if I hit any snags.

Best Regards,

Jorge Garcia

The mbed comes with ethernet support built-in. You'll need a magjack or equivalent to connect your mbed to a network.

I used the mbed workshop breakout board from Cool Components, which has a magjack ethernet connector, along with USB ports and a micro SD memory card slot. Maybe Farnell should stock it!

The mbed cookbook includes an implementation for an HTTP Server.

The server can serve hard-coded content, which is useful for testing, but it can also handle rpc calls and serve files. If you combine the webserver with the mbed's ability to write files to its flash-based file system you can do neat stuff.

To test this out, I wrote a simple graphic logic analyser. It waits for activity on the circuit under test and then captures samples every microsecond to memory. When it has enough samples, it writes out an svg file and starts up a web server to display the result.

On the right you can see it monitoring the I2C bus of an

arduino driving an LCD display. The program is under 90 lines long.

Great!!!

The ideea and the solution too.

Very cool!

Your code is well written, too.

Thanks for the post.

Gregory