VDI-RODERICO

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Does anyone have more info on this vdi https://youtu.be/293HXr8vIZw

[roderico]

VDI v1.4

I updated the firmwares of both LCD and LED versions with the following changes:

- ADC offset is set with the ADC value, i.e. without any conversion which should be more precise
- simple raising (+) or falling (-) edges on X and Y channels
- show VDI when op-amp is in saturation (although the value might not be reliable)
- show battery label when idle
- some compilation fixes

they should be more stable than previous versions if properly configured, maybe someone would like to give them a try and report any issue found with these new versions...

[roderico]

Hi Roderico,
I have added some lines of code to add backlight on or off, therefore the code added is few lines.
I saw the PIC16F876A has free space, there is the possibility to add other functions, I am thinking on how use it.

Why you tell overhead of the mcu?
The mcu is not continuously controlling the pin but the sw activate or deactivate this output only after a menu command, then the output remain latched.

Yes, the backlight is not essential but it is useful in some situations.
But who don't like or need it, can remove the transistor and two resistor involved.

Hi Sacchetti,
I thought you wanted to control the brightness level e.g. with PWM (this is implemented in the test firmware I uploaded that's why you need RC2) or by software, but if it is only on/off it would be fine only needs some extra components as you mentioned...

[Sacchetti]

Hi Sacchetti, ok no problem. The battery consumption is not the only concern, it takes memory and possibly add additional overhead to the mcu by continuously controlling the LCD backlight which in many situations is not essential unless you are using a blue display, very low light conditions, etc.

Hi Roderico,
I have added some lines of code to add backlight on or off, therefore the code added is few lines.
I saw the PIC16F876A has free space, there is the possibility to add other functions, I am thinking on how use it.

Why you tell overhead of the mcu?
The mcu is not continuously controlling the pin but the sw activate or deactivate this output only after a menu command, then the output remain latched.

Yes, the backlight is not essential but it is useful in some situations.
But who don't like or need it, can remove the transistor and two resistor involved.

[roderico]

Hi Roderico,
thank you.
However, I have already compiled the source code yesterday doing similar modifications/corrections but about backlight I have used RB0.
Please see up the message #57.

You are right, it is sure that with backlight on the power consumption increase but normally it is off.
In some conditions can be very useful.
This is a feature present in the LCD, why don't implement it?

It is possible also increase the value of resistor to have a reduced light but it will be readable enough.
In this case it is important to search an LCD having a led with low If (20mA).
If the battery is good there aren't problems.

Sorry, today I was too busy but can be I will do the prototype tomorrow.

Hi Sacchetti, ok no problem. The battery consumption is not the only concern, it takes memory and possibly add additional overhead to the mcu by continuously controlling the LCD backlight which in many situations is not essential unless you are using a blue display, very low light conditions, etc.

[Sacchetti]

Hi Sacchetti, I implemented the BL control in case you would also like to give it a try. Instead of RB0, you need to connect to RC2/CCP1 to test it, I also enabled PWRTE and changed the battery scale to the value you calculated (0xC. You might compare the two firmwares, i.e. without backlight control and with backlight control at 0% to see if there is significant difference in power consumption...

Hi Roderico,
thank you.
However, I have already compiled the source code yesterday doing similar modifications/corrections but about backlight I have used RB0.
Please see up the message #57.

You are right, it is sure that with backlight on the power consumption increase but normally it is off.
In some conditions can be very useful.
This is a feature present in the LCD, why don't implement it?

It is possible also increase the value of resistor to have a reduced light but it will be readable enough.
In this case it is important to search an LCD having a led with low If (20mA).
If the battery is good there aren't problems.

Sorry, today I was too busy but can be I will do the prototype tomorrow.

[roderico]

Can be I finish to build it tomorrow or the day after but I cann't complete tests immediately.

Hi Sacchetti, I implemented the BL control in case you would also like to give it a try. Instead of RB0, you need to connect to RC2/CCP1 to test it, I also enabled PWRTE and changed the battery scale to the value you calculated (0xC. You might compare the two firmwares, i.e. without backlight control and with backlight control at 0% to see if there is significant difference in power consumption...

[Sacchetti]

Ok Sacchetti, thank you, and as you mentioned in your previous post it would be interesting to see the results of your tests and how it works for you

Can be I finish to build it tomorrow or the day after but I cann't complete tests immediately.

[roderico]

Hi Roderico!
Your LCD is a chinese unbranded but working.

I have found this problem in a few LCD that I used in the past.
I bought them from a local distributor storing the datasheet in my hard-disk as usual but I don't remeber exactly where. As soon as I will found it then I will show you to see the source current on pin connected to GND. I remember this information was also present in that datasheet.

Ok Sacchetti, thank you, and as you mentioned in your previous post it would be interesting to see the results of your tests and how it works for you

[Sacchetti]

thank you for the info, in the tests I did with my LCD I didn't find much difference but I'll see if I can check it more carefully...

Hi Roderico!
Your LCD is a chinese unbranded but working.

I have found this problem in a few LCD that I used in the past.
I bought them from a local distributor storing the datasheet in my hard-disk as usual but I don't remeber exactly where. As soon as I will found it then I will show you to see the source current on pin connected to GND. I remember this information was also present in that datasheet.

[Sacchetti]

Hi Sacchetti, in the other pics MCLR is disabled since it is not used, but they will work without the pull-up resistor, however in microchip forums they recommend to add it even if it is disabled, e.g.

http://www.microchip.com/forums/m786296.aspx

http://www.microchip.com/forums/m729356.aspx

I also found pic16f88 was more stable for weaker signals in the adc reading when adding the resistor, if you could do some tests would be very good...

Hi Roderico!
I am trying to use these 16F876A because I used them some years ago not in a MD but in another circuit for a completely different usage, a Data Logger and at the end few of them remain spare. This afternoon (my GMT is different from yours) I went back to search the schematic of data logger and the code to see how I used this pin in SW and in HW and it was connected directly to VDD to use POR. The LVP was also at 0 therefore RB3 was used as a digital I/O.

The first link you are referring speak about 18F25K20 and the user has problem only in debug mode and this is a different family.
The second link speak about 16LF1503 that has the possibility to disable the pin and this micro is newer if compared to 16F876A.
I am referring only to my old but good 16F876A.

You are right, in a noisy environment can became a problem therefore I have modified the schematic connecting it directly to +5V.
But who prefer to use a resistor then can add it but it is not necessary.
I will do some test with the pin left before and connected to VDD after to see if the ADC work better.

Code and schematic updated will be published when I have finished to build it and completed the test.

[roderico]

Hi Roderico!

A little clarification.
I certainly did not explain it well.

Not all LCDs have pins that reach -500uA each if you connect them directly to GND.
I have found only a few who in certain conditions do so, others absorb less.
However on some datasheet is written but if you don't have it the only solution is check with a multimeter.
If you use a multimeter with min and max function then you can see also how change the current during the time.

thank you for the info, in the tests I did with my LCD I didn't find much difference but I'll see if I can check it more carefully...

[roderico]

Hi Roderico,
the pull-up resistor was used in the past with PIC having only POR.
This one (F876) has also PWRT and OST therefore is not more necessary if you use them.
You must connect the resistor only if you continue to use POR but it is worst, it is better to use PWRT or OST.
I prefer to attach the page where is explained.
[ATTACH]39823[/ATTACH]

Hi Sacchetti, in the other pics MCLR is disabled since it is not used, but they will work without the pull-up resistor, however in microchip forums they recommend to add it even if it is disabled, e.g.

http://www.microchip.com/forums/m786296.aspx

http://www.microchip.com/forums/m729356.aspx

I also found pic16f88 was more stable for weaker signals in the adc reading when adding the resistor, if you could do some tests would be very good...

[Sacchetti]

Hi Sacchetti, the reason to suggest to ground DB0-3 is to guarantee that their status is always in logical 0, however if you have found that it consumes 2mA more it is better not to ground them, since it appears not to cause any problem if they are not, I'll answer the other comments below..

Hi Roderico!

A little clarification.
I certainly did not explain it well.

Not all LCDs have pins that reach -500uA each if you connect them directly to GND.
I have found only a few who in certain conditions do so, others absorb less.
However on some datasheet is written but if you don't have it the only solution is check with a multimeter.
If you use a multimeter with min and max function then you can see also how change the current during the time.

[Sacchetti]

I am going to try to compile it...

Hi!
I have compiled it using XC8 free license, therefore the code is unoptimized. I am going to update the licence to PRO.

I have also done some little corrections/modifications to code (also PWRT) but I can not put here the file because it is not tested yet.
Please wait a moment and I will publish all.

Therefore stay tuned...