Edit - Arduino Stack Exchange

You are not logged in. Your edit will be placed in a queue until it is peer reviewed.

We welcome edits that make the post easier to understand and more valuable for readers. Because community members review edits, please try to make the post substantially better than how you found it, for example, by fixing grammar or adding additional resources and hyperlinks.

Required fields*

How i convert to Arduino Mega?

i need using OV7670 camera on my arduino mega, and i found this site have tutorial using ov7670 camera, but in this tutorial they use arduino Uno. if i'm using arduino Mega2560, what i need to do? do i have to change their code and pin connection ?

here is the link

https://www.instructables.com/id/OV7670-Arduino-Camera-Sensor-Module-Framecapture-T/?amp_page=true

Answer*

**Yes, you will have to change the code to match the Mega pinout**.

Because the program need to run quite fast, and the Arduino functions
`digitalRead()` and `digitalWrite()` are dead slow, the author of the
program used [direct port access][] for performing the raw IO.
[For example][]:

```c++
	//Wait for vsync it is on pin 3 (counting from 0) portD
	while(!(PIND&8));//wait for high
	while((PIND&8));//wait for low
```

This is testing pin PD3 (8 is 2<sup>3</sup>), which on the Uno is
digital&nbsp;3, but on the Mega is digital&nbsp;18. The same code could
be written in a portable fashion:

```c++
	//Wait for vsync it is on pin 3 (counting from 0) portD
	while (digitalRead(3) == LOW); //wait for high
	while (digitalRead(3) == HIGH); //wait for low
```

but it would probably be too slow.

Note also that here:

```c++
 UDR0=(PINC&15)|(PIND&240);
```

the program takes advantage of the particular pin mapping of the Uno in
order to read 8&nbsp;inputs with only two port reads (4&nbsp;bits on
port C and 4&nbsp;bits on port D). You could do even better on the Mega
if you use pins A8 through A15 for the data bus, and then read the whole
8-bit word as `PINK`.

There may be some other differences between the Uno and the Mega that
need to be taken into account, but the pin mapping is the only one that
is obvious to me just by quickly going through the code.

[direct port access]: https://www.arduino.cc/en/Reference/PortManipulation
[For example]: https://github.com/ComputerNerd/ov7670-no-ram-arduino-uno/blob/d64dcf0a8c9c04c5b4c5fe1da01fd2c6d9b35600/main.c#L34-L36

Draft saved

Draft discarded

Edit Summary*

Cancel

hello, you said that "..which on the Uno is digital 3, but on the Mega is digital 18." how do you know on the Mega is Digital Pin 18? and i still don't understand about use pins A8 through A15 and read the word as PINK

Ibnum Richaflor
– Ibnum Richaflor

2019年09月10日 03:47:18 +00:00
Commented Sep 10, 2019 at 3:47
@IbnumRichaflor: Re "how do you know [...]": Google "Arduino Uno pinout" and "Arduino Mega pinout". Re "use pins A8 through A15 and read the word as PINK": Pins A8 – A15 (Arduino labeling) are PK0 – PK7 (manufacturer's labeling), collectively known as "port K".

Edgar Bonet
– Edgar Bonet

2019年09月10日 07:35:40 +00:00
Commented Sep 10, 2019 at 7:35

Add a comment |

How to Edit

Correct minor typos or mistakes
Clarify meaning without changing it
Add related resources or links
Always respect the author’s intent
Don’t use edits to reply to the author

How to Format

create code fences with backticks ` or tildes ~
```
like so
```
add language identifier to highlight code
```python
def function(foo):
print(foo)
```
put returns between paragraphs
for linebreak add 2 spaces at end
_italic_ or **bold**
indent code by 4 spaces
backtick escapes `like _so_`
quote by placing > at start of line
to make links (use https whenever possible)

<https://example.com>

[example](https://example.com)

<a href="https://example.com">example</a>

formatting help »
answering help »

How to Tag

A tag is a keyword or label that categorizes your question with other, similar questions. Choose one or more (up to 5) tags that will help answerers to find and interpret your question.

complete the sentence: my question is about...
use tags that describe things or concepts that are essential, not incidental to your question
favor using existing popular tags
read the descriptions that appear below the tag

If your question is primarily about a topic for which you can't find a tag:

combine multiple words into single-words with hyphens (e.g. arduino-uno), up to a maximum of 35 characters
creating new tags is a privilege; if you can't yet create a tag you need, then post this question without it, then ask the community to create it for you

popular tags »