Facebook
Google
GitHub
Linkedin
If Im writing mcp1.begin(); it only works for the first IC. The second IC, remains dead.
If Im writing mcp1.begin(0x20) or mcp1.begin(32) nothing works.
In both cases I get no errors from the compiler.
How to link 2x MCP23017 together ?
- Thread starter q12x
- Start date
If Im writing mcp1.begin(0x20) or mcp1.begin(32) nothing works.
In both cases I get no errors from the compiler.
The object you named mcp1 can access the 16 ports on the first chip. The object you named mcp2 allows to access its ports. You have to use the object that corresponds to the chip whose address it was given to get to that chips ports.
Do you understand?
A casual observation here. I program in assembler, I didn't quite start before C was invented but certainly before ANSI C was invented. Nowadays, I program ARMs in assembler. I've never found C to be that helpful, generally it seems to make what I want to do more complicated; although there must be applications where C does the job better than assembler they just aren't the applications that I am writing.
When I want to get a external IC to do something. I look it its datasheet, and find what data has to go in what register. Then I look in the manual for the microprocessor I am using and write the data to the register in the I2C peripheral, to cause it to send the appropriate data to the external device, and I generally get it working quite quickly.
I see an awful lot of posts on these fora where people can't get peripherals to work, and it generally seems to be a problem with something called a "driver".
My observations on drivers suggests that they are badly written and atrociously documented, and often from dubious sources, and it doesn't surprise me that they don't work.
I've used the MCP23017 before, controlled by some Microchip part - I forget which, and it seemed to work quite readily - the difference was I didn't employ a "driver".
When I want to get a external IC to do something. I look it its datasheet, and find what data has to go in what register. Then I look in the manual for the microprocessor I am using and write the data to the register in the I2C peripheral, to cause it to send the appropriate data to the external device, and I generally get it working quite quickly.
I see an awful lot of posts on these fora where people can't get peripherals to work, and it generally seems to be a problem with something called a "driver".
My observations on drivers suggests that they are badly written and atrociously documented, and often from dubious sources, and it doesn't surprise me that they don't work.
I've used the MCP23017 before, controlled by some Microchip part - I forget which, and it seemed to work quite readily - the difference was I didn't employ a "driver".
In this case he is using a library provided by Adafruit. Most of the documentation for many libraries consists of examples and the source. A neophytes often has a lot of difficulty doing things that stray from the examples.
The assembler-like activity is encapsulated in the library. For some things the C layer makes things much easier, for some it can be confusing.
I think this is a simple case but there are so many moving parts it is going to require trying it myself so I can see what might be missing.
Thank you, I am very happy we push it until here, to be honest. I knew this will be a long day.
I mentioned already, that when I FIRST open and install the latest driver for MCP23017 in arduino,
the newest versions 2.0.3 or 2.1.0, throw me big red error and nothing worked.
It didnt recognised "#include "Adafruit_MCP23017.h"" which was very bad.
My solution: I installed an older version 1.3.0, and is working fine now.
You are right, its always a driver problem... I have plenty experience with them as well, for diverse things along the years.
Hmmmm you give me an idea, maybe I have to revert further back in driver versions? until something gives?
Code:
#include "Adafruit_MCP23017.h"
Adafruit_MCP23017 mcp1; //Instantiate mcp1 object
Adafruit_MCP23017 mcp2; //Instantiate mcp2 object
void setup()
{
Serial.begin(19200);
mcp1.begin(0x20);
mcp2.begin(0x21);
/* configuring ALL GPIO as output. */
for(int i = 0; i <= 15; i++)
{
mcp1.pinMode(i, OUTPUT);
mcp2.pinMode(i, OUTPUT);
}
}
//this code should make both IC's drive their leds in the same time for the same pins.
int dly = 100;
void loop()
{
for(int i = 8; i <=31; i++)
{
mcp1.digitalWrite(i, HIGH);
mcp2.digitalWrite(i, HIGH);
delay(dly);
mcp1.digitalWrite(i, LOW);
mcp2.digitalWrite(i, LOW);
delay(dly);
}
}
That is not a driver, it's a library. You need to install the latest and use the right name for the constructor which will be in the example code. The older version will have unpatched bugs and potentially other problems. Always use the latest unless you know there is a bug or incompatibility.
And as a reminder, here is the circuit Im currently using:
with exactly 3.3V on A0 as in the diagram here
Also, you can see in the image 2 pull up(to+5V) 4.7k resistors on both serial lines, on the bottom board.
The yellow wire is 3.3V going to A0 pin.
And when I mention the first IC works, I mean the top one in the picture, with 8leds on it
while the second IC, in the bottom has 4leds
Both ICs have the leds on their portB.
with exactly 3.3V on A0 as in the diagram here
Also, you can see in the image 2 pull up(to+5V) 4.7k resistors on both serial lines, on the bottom board.
The yellow wire is 3.3V going to A0 pin.And when I mention the first IC works, I mean the top one in the picture, with 8leds on it
while the second IC, in the bottom has 4leds
Both ICs have the leds on their portB.
I dont know how to install a driver for this MCP chip!
Last edited:
AlbertHall
- Joined Jun 4, 2014
- 12,629
The version 2.1.0 library example uses "#include <Adafruit_MCP23X17.h>" in the example code.
Perhaps start with the LED Blink example and work out from there?
Perhaps start with the LED Blink example and work out from there?
Where can I find this library example code that you mention? Can you give me your root to it?
There is no driver. The library is all you need. If you use the right name, it should work.
