ESP8266 Community Forum

Arduino IDE v 1.6.4 - Driver implementation for MAX7219 - 8 Digit Display Modules:

For reference: http://www.esp8266-projects.com/2015/06/arduino-ide-max7219-8-digit-display.html

Hi,

I just saw yours. I had already made some sketches to drive those 7219 boards using the LedControl Arduino lib. (It supports matrix displays as well.) Looks like your lib has built in number conversion, which I had to do myself since I believe the LedControl only lets you set one digit at a time.

Were you aware of LedControl and wanted to improve on it?

I will have to try yours out. I basically made a remote display module that runs a web server and let's you change the numbers displayed on the 7219 module remotely via a simple GET query string like http://xxx.xxx.xxx.xxx/num?n=12345678

I just finished one for a 14 segment display as well, which I have to multiplex myself from the ESP (see my other thread). Needs a little cleanup, and might have a memory leak I have to look at tomorrow. This one lets you send a scrolling message to it remotely. It is alpha numeric (14 segment). I designed my own lib for it to be driven with shift registers, and created a font for it segment by segment.

Maxim has a chip to drive 14 segment displays, but it is a lot pricier than the 7219, and I don't think there are any cheap Chinese clones of it yet, like the counterfeit chips in most of those modules (Google counterfeit max 7219 to see how to tell... Not that I have found the fakes to be any worse, though they don't support Maxim for their efforts.)

Anyway, nice work. What is that graph of Vdc in your video? Is it feeding the data to the display via serial?

FlyingHacker wrote:Hi,

I just saw yours. I had already made some sketches to drive those 7219 boards using the LedControl Arduino lib. (It supports matrix displays as well.) Looks like your lib has built in number conversion, which I had to do myself since I believe the LedControl only lets you set one digit at a time.

Were you aware of LedControl and wanted to improve on it?

I will have to try yours out. I basically made a remote display module that runs a web server and let's you change the numbers displayed on the 7219 module remotely via a simple GET query string like http://xxx.xxx.xxx.xxx/num?n=12345678

I just finished one for a 14 segment display as well, which I have to multiplex myself from the ESP (see my other thread). Needs a little cleanup, and might have a memory leak I have to look at tomorrow. This one lets you send a scrolling message to it remotely. It is alpha numeric (14 segment). I designed my own lib for it to be driven with shift registers, and created a font for it segment by segment.

Maxim has a chip to drive 14 segment displays, but it is a lot pricier than the 7219, and I don't think there are any cheap Chinese clones of it yet, like the counterfeit chips in most of those modules (Google counterfeit max 7219 to see how to tell... Not that I have found the fakes to be any worse, though they don't support Maxim for their efforts.)

Anyway, nice work. What is that graph of Vdc in your video? Is it feeding the data to the display via serial?

Didn't know about your project, sounds interesting, do you have a link with more details?

Yes, I 've done a separate conversion function, been interested only on float positive values.

Also found a nasty BUG in dtostrf() STDLIB function. See details and fix here:
http://www.esp8266-projects.com/2015/06/arduino-ide-nasty-bug-in-dtostrf.html

The graph is the output of a 34401A multimeter captured real-time thru Agilent BenchVue software and is used just as a comparation with the ESP8266 ADC read displayed values, for a very crude accuracy test. And as you can see is not looking to bad at all.

Oh, the LedControl library is not my project. I just used it in one of my projects.

http://playground.arduino.cc/Main/LedControl

It is decent, but could use some built in simple number printing functions, especially floating point like yours. In my application I did fixed point and manually set the decimal point as a cheat/hack.

Perhaps you could combine yours with the existing lib to expand upon it.

Those seven segment display modules are really fun, and so cheap on eBay. The matrix displays are cool too if you want something bigger (but more pixelated). They come as kits on eBay for under $2. The SMD versions are smaller and you only have to solder the headers on. There are through hole kits too, where you solder the socket and a resistor and capacitor or too, plus the headers. However, those are a little bigger, making it harder to chain them together.

The LedControl library seems more focussed on the matrix displays (at least it has more functionality with them).