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16  Using Arduino / General Electronics / Re: DC to DC boost converter on: October 14, 2013, 07:07:27 am
I think taht there is no step-up in this voltage class. Problem should be input voltage - 2,9V is really small to step-up to more than 5V. Yes,many these converters that has so low input steps only to 5V max. The cheapest way is to use step-up to 5V and second boost to 24V. That could be possible, but not with one boost converter.
17  Using Arduino / General Electronics / Re: I2C bus being "jammed" on external PSU? (on USB OK) on: October 14, 2013, 06:51:46 am
OK, so revisited all components.

Added 1000 microF capacitor at Arduino power input pin. Also added 10R resistor to "lighten" the Arduino line regulator.
Still no effects.

I am slowly getting out of ideas ... smiley-roll
18  Using Arduino / General Electronics / Re: I2C bus being "jammed" on external PSU? (on USB OK) on: October 13, 2013, 03:32:08 pm

There's a simple way to find out if current is the problem - measure it!

Watch the voltage on the +5V pin, see if it drops under load.

I thought about it since first reply. So I have measured it and doesnt seems to be problem - voltage is constant at 4,94 V.
But idea inspired me that there might be peak voltage drops in very short times - e.g. in 1 microsecond or so - this will definitely affect hi-speed SPI that runs in 8 Mhz. I also looked at 5V voltage under oscilloscope, but seems linear.

I will try adding 1000 mikroF capacitor at input, maybe it will help.
19  Using Arduino / General Electronics / Re: I2C bus being "jammed" on external PSU? (on USB OK) on: October 13, 2013, 01:48:45 pm
Might be huge current...

But, Vin pin is connected to onboard regulator - isnt it? So i have to power lcd backlight out of arduino?
I will try to use DC-DC step-down, cause instrument should be powered from 12V battery. Also I have High Voltage converter for 12V and it consumes huge current.

How much current does SD card consumes? I have a converter that provides 5V 500mA from 12V, would it be enough for MCU and SD?
20  Using Arduino / General Electronics / I2C bus being "jammed" on external PSU? (on USB OK) on: October 13, 2013, 12:46:56 pm
Hi all,

I have been working on our next detection system quite long. Overall have great experience with Arduino for about three years almost without any bigger problems.

Now I am modernising some very old precise measurement equipment.
Basic scheme of operation - reading analog sensor with voltage divider and doing some mathematical stuff with it (and printing to serial port, lcd display, and SD card).

But, even my project is almost finished (from software point of view), I have faced following huge problem:

This is NOT a software issue, when powering  from USB everything works fine !!!

When arduino is connected to +12V power supply (I have tested 3 different), all serial SPI devices doesnt work as they should.  Arduino onboard regulator seems to heat a lot, but there is very low ambient temperature (about 10 Celsius degrees) so it shouldnt affect this.

The colour SPI LCD (ST7735) displays a random data when it has to display bitmap from SD:

Otherwise when I write black to full screen it works fine:

Also rewriting small areas with lines and text works fine:

And the main problem - when trying to read/write data to SD card causes havoc on card (BTW file RSSlog.TXT created by Arduino is empty):

Here is a image how the components are wired (for illustration only, sorry fro mess around):

Any ideas what could cause this?
I am thinking about some kind of interference or jamming from pulse converters (detector needs negative 12V and negative 300V). I also added a ferrite core filter on data wires, but it seems not having some remarkable effect....

Thanks in advance ! smiley-wink
21  Using Arduino / Displays / Re: ST7735R LCD shield w/ SDcage - not working on Mega 2560? on: January 16, 2013, 01:37:58 pm
Oh, right it is definitely the thing i thought of...

I maybe wrote in not so good to understand english. I am not a native speaker, sorry about that.

So now I know that for use on Mega I have to do a wirings and that I cant use this shield as a shield (directly plugged on mega) but have to wire it to equivalent connection you mentioned.

Thanks for your very PROPER and SIMPLE explanation. This really helped for exact problem solution - had increased your Karma twice smiley-wink
22  Using Arduino / Displays / Re: ST7735R LCD shield w/ SDcage - not working on Mega 2560? on: January 15, 2013, 06:20:18 pm
SPI isn't on 11,12,13 on Mega2560

They are just normal pins, that's why there is no difference in speed.

The SPI on Mega2560 is on 50,51,52 and the ICSP header. 53 is hardware SS.

Sorry, but didnt you thought that there IS a difference in speed?

And I am using these pins on Mega with sample code and it "works" , but there is described slowness in speed of redrawing... Might these be solved with soldering a wires and reconnect it on above pins you spoke about?
23  Using Arduino / Displays / Re: ST7735R LCD shield w/ SDcage - not working on Mega 2560? on: January 15, 2013, 05:35:09 pm

display in standart demo code uses these libraries:
<Adafruit_GFX.h>    // Core graphics library
<Adafruit_ST7735.h> // Hardware-specific library

Will look on SPI clock later. As I understand it could run at 8 Mhz max (or in double divided freqs)?

But might found an answer why the lcd is slow on Mega - found this video:

Its test of the same LCD (but in non shield version) running the demo code on Leonardo (? - not sure it it is Leonardo smiley-wink) As in this comparison the LCD in SPI works much faster than in "simple connection" (?GPIO). Mine display shield is behaving same slow, as on "simple connection". Ran the exactly same code as in video.
Could it mean, that if I use other pins than SPI marked on Mega that it causes the slow because general digital pins has slower data output rates than serial marked ones?

(code example uses : cs 10      //LCD Chipselect; dc 9       //LCD Data or Command; sclk 13    //Hardware SPI SCLK; mosi 11    //Hardware SPI MOSI)

Thanks for ideas smiley
24  Using Arduino / Displays / Re: need fast lcd on: January 11, 2013, 04:01:39 pm
Could anyone confirm me, that SPI LCDs are much slower than parallel (8 or 16 bit) connected ones?
I am asking because mine with ST7735 redraws really slow (2sec for full screen area) and I want to know if this is normal or if it needs some tweaks or library mods.

SSD1289 driver is hopefully often used in modules sold on ebay and DX.. Looking for one of them, but rather prefer something smaller (around 2") - will continue searching, listings are thousands of tft`s.

Many displays modules with SSD1289 are not directly pluggable into Arduino, I need a shield pin converter - understood. But these pin converter PCB`s are without active components, aren`t they? I`d like to save my money and do a connection with female to male cables if it is possible.
25  Using Arduino / Displays / Re: need fast lcd on: January 09, 2013, 05:58:42 pm

I also have a question about display speed...  Now I have bought display module with ST7735R and it has SPI connection. great because not so much wires are required...
But I have spotted very lack of speed in complete display redraw (or of huge areas). Full display rewrite can take about 2 second (I guess, but it is well seen). This write speed is really insufficient in my project - is it caused by limits of SPI bus or library optimalization ?

Am I right guessing that display on parallel connection redraws whole display area much faster?
I looked on video on first post - display seems to redraw faster and as I see a lot of wires it should be parrallel connected...
26  Using Arduino / Displays / Re: ST7735R LCD shield w/ SDcage - not working on Mega 2560? on: January 09, 2013, 05:50:56 pm
Yes, you are completely right Unfortunately the modding the libs can be only possible if desired pins are not required by other devices which is sadly my case... But probably I will sell this shield and buy another display module.
But spotted that ST7735 is slow for my needs - posted a question in newly posted thread by another user - it has suitable topic name for my question smiley-wink

Thank you for your time !
27  Using Arduino / Displays / Re: ST7735R LCD shield w/ SDcage - not working on Mega 2560? on: January 07, 2013, 12:05:54 pm
Thanks for reply !

I thought about this problem - both devices (LCD and SD) uses SPI and it need slave select (SS) which is on pin 55 on mega.
So my ideas of what causes SD not working were correct...

I just wanted to ensure about it - thank you.
28  Using Arduino / Displays / ST7735R LCD shield w/ SDcage - not working on Mega 2560? on: January 06, 2013, 07:16:20 am
Hi all,

few weeks I have sold my Arduino Uno and bought a Mega 2560 instead (my projects were growing up and there were not enough digital pins for me  smiley smiley ). Now I am getting first experiences with Mega and its capabilities/differences compared to Uno.

I have bought an colour SPI 1,8" LCD shield (using ST7735R controller) with keypad buttons.
Here is a link:
Even I got it working with Adafruit LCD library after few tweaks.
Nice piece of hardware. There is also a microSD card reader onboard, and thats why I have bought it.

BUT smiley-roll If I use his demo code (ready to download on item page) it simply doesnt work. Says that init of SD card failed.
When I gathered informations about SD card pins, found out that there are different connections on Mega boards (compared to Uno boards). Also found that on some these lcd shields sellers are noticing that on Mega`s SD doesnt work....

Also tried simple SD card example from Arduino IDE, with no luck...

Any ideas what to try next / or where could be problem ? I want to write him that this shield is not fully Mega compatible, but want to ensure that I am not doing anything bad....

29  Using Arduino / Networking, Protocols, and Devices / Re: Few advanced questions about Ethernet shield on: July 09, 2012, 01:42:51 am
Have a look at this:

I know Cosm (former Pachube). It is nice, but it looks like it is not possible to display all my sensors in one map. So we will probably use own solution - currently the idea is to use OSM map background and a point layer with sensor stations in graduated colors according to their measured values and maybe additional page(s) with station details (description, history etc.).

The idea was, that the "customer" can display a local webpage from his own sensor station to check current values (this solution would eliminate the need of multi-platform desktop client GUI SW) while the station would always send the values also to the internet - to a server which would collect all the data feeds and display them in a map etc.
30  Using Arduino / Networking, Protocols, and Devices / Few advanced questions about Ethernet shield on: July 08, 2012, 06:29:04 am
Hi guys,

I would like to tell you that I'm not a noob. I am using Arduino Uno for quite some time and already successfully wrote several advanced programs (without help from others). So this is my first post, when need some help, because I didnt find satisfactory answers on the Internet smiley-wink

My brother asked me to participade on hardware solution for highly specialized let me say "sensor site" for municipal use. Because work assignment was to be completely open-source sw and hw device, Arduino seems to be the simpliest and best solution at this time.
Each device will be arduino with few sensors, character LCD and ethernet shield. Every device will show its measurements on LCD and on specified local webpage but we need to know whether standard Ethernet Shield can do:

1.) send a web page (static html) not only locally (know that local broadcast is possible), but also directly to the Internet network (multicast) - to give access from anywhere, not just form local network.

2.) send "data stream"  - to  enable data to be fetched directly from one server (we dont want to parse html with servers...)

3.) whether it is possible to run local and internet broadcast at a same time (i.e. after delay but still in one program loop).

4.) how many pins (and which ones) are used by etherne :smiley-eek:t shield? Sorry, already found this somewhere but lost it again...  smiley-mad

I am asking because I dont have ethernet shield and never used it - we will purchase it with arduino in few days after all of last details will be checked .

Thanks for ALL answers ! smiley-cool
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