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I'm doing a project in which I need to use DAC-s to conduct voltage to dimmers to switch appliances on or off.

So far I've used Adafruit's guide and it worked fine. I got the I2C working and sudo i2cdetect -y 1 showed my DACs to be at 0x62. It also worked when testing the setup with the simpletest.py.

The next issue I'm facing is that there are 4 DACs and I need to be able to give each of them a separate value.

Here are the schemas:

Scheme_1 enter image description here

As I understand I need to use these:

  • SEL1(GPIO pin 12)
  • SEL2(GPIO pin 11)
  • SEL3(GPIO pin 16)
  • SEL4(GPIO pin 18)

to access the I2C "slaves" and change their addresses according to this, another Adafruit guide.

How would I go about doing this in e.g. changing the Adafruit code to do that?

slartibartfast
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1 Answers1

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You need to ensure only one device has I2C address 0x62 at any one time.

SEL1(GPIO pin 12)
SEL2(GPIO pin 11)
SEL3(GPIO pin 16)
SEL4(GPIO pin 18)

Initially set each of the pins high so that each device is at I2C address 0x63.

When you want to access a device set its pin low. That device will now be at address 0x62 and may be accessed through I2C. When you have finished with the device set its pin high.

Only one of the device pins must be low at any one time.

joan
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  • Something like this link?

    The problem is, I only have my RPi at home. Multimeter, the DACs and everything else are at the site, where I will get to go tomorrow.

     – slartibartfast Apr 10 '18 at 18:42
  • Yes, that is doing as I described. – joan Apr 10 '18 at 18:57
  • To expand on this, Joan's instructions were helpful and led me to the result I hoped to achieve. Although I struggled with a newbie problem when setting the pins high or low.

    GPIO.setmode(GPIO.BCM) and GPIO.setmode(GPIO.board)

    are quite different. Here is a good explanation.

     – slartibartfast Apr 29 '18 at 09:21