Raspberry Pi Forums

Hi

a week ago i bought a MCP23017 and hooked it up



Just without the leds and button,and i tried to get the GPIO's on it to put out 3.3v
by doing this

gpio load i2c
gpio i2cd

gpio -x mcp2301720 mode 100 out
gpio -x mcp2301720 write 100 1


Ive checked and the mcp is on 0x20, but i cant get 3.3v on pin 21 (GPA0)

Im not sure if i get things mixed up, or what ells im doing wrong

Hope someone can help me

Have you followed the adafriuit guide on getting i2c set up ?

https://learn.adafruit.com/adafruits-ra ... guring-i2c

Does your 23017 show up in the i2cdetect output ?

PeterO

Its does show up as 0x20
but there is a UU device showing also

You can safley ignore the UU device...

Ok so the problem must be in the programming of the 23017.

I'm sorry but I'm not familiar with the commands you are using to configure the 23017 (I do it from 'C' code).

PeterO

is it easy to do the same thing in C?

What im looking for is a way to control a bunch of relays from the
pi , using a mcp23017

Install wiringPi and take a look at this: http://wiringpi.com/extensions/i2c-mcp23008-mcp23017/

Guess ill have a look again,

Got my command from Gordon(wiringpi) him self
wrote to him about howto.

But this looks like C? im only just learning C, been
using #bash for some years now

I was not suggesting you should do it in 'C', I was pointing out that because I'm only familar with using I2C from C I couldn't help you further.

PeterO

gpio load i2c
gpio -x mcp230170x20:1 write 100 1
gpio -x mcp230170x20:1 write 101 1
gpio -x mcp230170x20:1 write 102 1
gpio -x mcp230170x20:1 write 103 1
gpio -x mcp230170x20:1 write 104 1
gpio -x mcp230170x20:1 write 105 1
gpio -x mcp230170x20:1 write 106 1
gpio -x mcp230170x20:1 write 107 1

gpio -x mcp230170x20:1 write 100 0
gpio -x mcp230170x20:1 write 101 0
gpio -x mcp230170x20:1 write 102 0
gpio -x mcp230170x20:1 write 103 0
gpio -x mcp230170x20:1 write 104 0
gpio -x mcp230170x20:1 write 105 0
gpio -x mcp230170x20:1 write 106 0
gpio -x mcp230170x20:1 write 107 0

what is :1 for

darkgeej wrote:what is :1 for

I think it's for output - that worked for me. Read the code (because the man page for gpio is incomplete on the subject of -x extensions).

Still nothing on pin 21 = 0v

it worked XD just a bad connection

so the :1 did the trick its magic

darkgeej wrote:it worked XD just a bad connection

so the :1 did the trick its magic

I thought the 0x20 instead of 20 would actually do the trick

darkgeej wrote:Guess ill have a look again,

Got my command from Gordon(wiringpi) him self
wrote to him about howto.

But this looks like C? im only just learning C, been
using #bash for some years now

And I missed the 20 which should have been 0x20. Probably not enough coffee when I replied to the email!

-Gordon

DirkS wrote:

darkgeej wrote:it worked XD just a bad connection

so the :1 did the trick its magic

I thought the 0x20 instead of 20 would actually do the trick

The bit of code that parses the -x flags to the gpio command stops parsing when it has had enough - so:

gpio -x mcp230170x20:1 write 105 1

works, but the extra :1 on the end is ignored. You can put anything there and it's ignored...

The real issue here was not prefixing the I2C address with 0x - of-course we could have used decimal (32)...

-Gordon

Anyway, it worked thanks to u all for guiding a lost noop

I have boards for driving 8 relays and it has a mcp23017 on board. The boards are designed so that a second board can be driven from the first (Port A)

I wrote some demo code for the MCP23017 relay board. It turns on and off various Port B pins (IC Pins 1-8)

Here it is.

gordon@drogon.net wrote:

DirkS wrote:

darkgeej wrote:it worked XD just a bad connection

so the :1 did the trick its magic

I thought the 0x20 instead of 20 would actually do the trick

The bit of code that parses the -x flags to the gpio command stops parsing when it has had enough - so:

gpio -x mcp230170x20:1 write 105 1

works, but the extra :1 on the end is ignored. You can put anything there and it's ignored...

The real issue here was not prefixing the I2C address with 0x - of-course we could have used decimal (32)...

-Gordon

First of all thanks a lot for the amazing work you've done with WiringPi.
Can I just suggest you to update the example on the extension page? Since I have myself lost a decent half hour trying to figure out why nothing was being output, when in fact the I2C adress was incomplete (using 20 instead of 0x20), I'm sure many will benefit from the update.
http://wiringpi.com/the-gpio-utility/i2 ... xtensions/