You may know your way around the registers of that favorite microcontroller, but at some point you’ll also need to wield some ninja-level math skills to manage arrays of data on a small device. [Scott Daniels] has some help for you in this arena. He explains how to manage statistical calculations on your collected data without eating up all the RAM. The library which he made available is targeted for the Arduino. But the concepts, which he explains quite well, should be easy to port to your preferred hardware.
The situation he outlines in the beginning his post is data collected from a sensor, but acted upon by the collection device (as opposed to a data logger where you dump the saved numbers and use a computer for the heavy lifting). This can take the form of a touch sensor, which are known for having a lot of noise when looking at individual readings. But since [Scott] is using the Mean and Standard Deviation to keep running totals of collected data over time it is also very useful for applications like building your own home heating thermostat.
For those that grabbed one of these TM1638 UI boards you can now easily use it with your Stellaris Launchpad. [Dan O] took it upon himself to publish an ARM library for the UI board.
There’s not a lot of new stuff to talk about here. We’ve already seen this being driven by an FPGA. [Dan] also links to both an Arduino and an MSP430 library for the board. The one thing that is good to know is that the board seems to run fine from the 3.3V supplied by the Stellaris Launchpad.
The ARM chip has four different hardware SPI modules which could have been used to drive this display. But [Dan] opted to bit bang instead. This give him more flexibility, like easily changing the pin mapping and foregoing the need for external components. All it takes is direct connections from three I/O pins which are used for clock, data in, and data out. We’ve embedded the obligatory demo video after the break.
Continue reading “Stellaris Launchpad library to drive the TM1638 UI board”
[H. Smeitink] got his hands on a 320×240 color TFT LCD screen. He set out to drive it with a small PIC microcontroller but didn’t find a lot of help out there to get up and running quickly. This is surprising since it’s a really nice display for quite a low price (under $16 delivered on eBay at the time of writing). He decided to write his own library and support tools to help others.
The display includes an SPI touch screen, but since that works separately from the LCD controller, touch input is not supported in this package. The driver that he wrote is coming from a mikroC toolchain point of view, but it shouldn’t be too hard to port to your platform of choice. We took a quick look at the code and it seems all you need to do is tweak the defines to match your hardware registers, and implement your own delay_ms() function.
But he didn’t stop with the driver. You’ll also find a C# program which converts images to an array for easy use on the display. Incidentally, this is the same display which [Sprite_TM] got working with the Raspberry Pi.
Kicad is a fantastic PCB layout tool. We think creating a part for use with Kicad is in many ways easier than in Eagle, but it never hurts to have a few shortcuts. Here’s a new way to quickly get your parts into the schematic editor. It’s a Python script that generates symbols from an XML input file. You create the XML file with a list of all the pins on your part and the function they will serve. The Python script will then format that as a library file which can be imported by Kicad.
It’s a little bit clunky due to the number of steps in the process. But it is possible to use a CSV file generated in a spreadsheet program to create the XML needed by the script. We’ve used the online component builder ourselves, and appreciate the possibility of mass pin assignments instead of the drop-box for every pin as used by the web interface. One time we were 20 pins into the naming process and accidentally refreshed the page… ugh!
The code is available in their git repository, with a description of the XML format, and a wiki tutorial outlining the component building process. After you give it a try we’d love to hear what you think in the comments.
Servo8bit is a library for AVR microcontrollers that allows you to drive servo motors without the need for a 16-bit timer. Obviously, this is quite useful for smaller chips that only have 8-bit timers and it is specifically targeted at the ATtiny45 and ATtiny85 microcontrollers. The library offers 256 steps of resolution, and can drive up to five servos at one time. Servo control pulses can be generated between 512 and 2560 microseconds and if you don’t mind increasing the time between these pulses [Liya] says it would be possible to increase the 5-servo limit.
The library is quite easy to use, but in its current state it would take just a bit of work to port to another device. It’s been written for an 8 Mhz clock signal with PortB used to drive the motors. Using find-and-replace to change the PORTB keywords to use a DEFINE variable should be easy enough, but we don’t know how hard it would be to change the clock frequency.
We wonder if it’s possible to make this a slave device, perhaps implementing a 1-wire protocol?
We’ve been hiding away in air-conditioned comfort to wait out the hot weather afflicting most of the US right now. Luckily we’re keeping busy with the great links coming into our tips box.
[Brett] sent us a note about his work on the new Arduino PID library. He is the author of the original library and recently decided it was time for a ground-up rewrite. But along the way he took the time to explain PID control and the choices he made during development.
We see a lot of PID controllers around here, like this router based espresso machine add-on. Proportional-Integral-Derivative Controllers are a way to make sure the control you intended to get from your devices is actually achieved in practice. They monitor a process and accumulate results over time in order to account for future events. From what we’ve just described you can see why the subject needs to be demystified.
Get yourself elbow-deep into [Brett’s] article. He does a great job of discussing each issue, and uses a multitude of easily understandable graphs to show the hurdles each portion of code is meant to overcome.
When [Bill Porter] works on a project, he says that he typically writes his own NMEA standard communications protocols to fit the job at hand. While it makes things easy to troubleshoot, he admits that his custom protocols are wasteful of both processor time and bandwidth. Binary communications on the other hand are more efficient, but a bit trickier to manage.
To make things easy for the common user, he wrote a library called EasyTransfer which abstracts packetized serial communications between two Arduino boards. The process is pretty simple – all one has to do is define a data structure on both Arduino boards so that they know what sort of data is coming over the wire, and EasyTransfer handles the rest. This allows users to worry less about communications protocols or transmission errors, and focus on their projects instead.
If you’re working on a project and searching for an easy way to get a pair of Arduinos talking, swing by his site and grab the library. It doesn’t get much easier.