5 ms·

It's very easy to remove the pull up resistors from most break out boards. The most likely issue you will encounter with trying to connect many I2C devices is

It's very easy to remove the pull up resistors from most break out boards. The most likely issue you will encounter with trying to connect many I2C devices is address collisions where devices have fixed addresses or at least some fixed bits in the address. This will probably limit you to about twenty or thirty useful devices on a bus.

ashtonkem 6y ago
You can get around this with an I2C multiplexer[0]. It allows you to connect 8 devices to the multiplexer and then occupy one address on the main bud. 0 - https://www.adafruit.com/product/2717 https://www.adafruit.com/product/2717
fh973 6y ago
How is the allocation of addresses done typically? Are they always hardcoded? Is the same chip then available with different addresses (different SKU)?
- aulin 6y ago
  most common practice I've seen at least with typical arduino/rpi sensors is fixed address for the same chip, sometimes you can change one or two bits so you can have two/four of the same kind in the same bus, sometimes you have address conflicts with similar devices from the same manufacturer (e.g. bosch bme680, bme280 and bmp180).
- pantalaimon 6y ago
  Typically addresses are only 7 bit (10 bit are possible but not all devices support that). So you either have way to set the address using resistors / address lines or you have some config more where you set the configuration for the sensors one by one (Cypress touch sensors had this)
- magicalhippo 6y ago
  > Is the same chip then available with different addresses This is sometimes done, though more commonly in my experience is there are some input pins which the chip uses to determine the actual address. This might be as simple as one to three inputs which should be connected to ground or supply voltage to encode the last bits of the address. Other chips are a bit more creative, and allows you to, in addition to ground and supply, tie the address pins to the I2C clock and data pins. This allows it to generate four combinations from per address pin.
- moftz 6y ago
  People have already touched on setting the addresses using the pins but sometimes you can just buy near identical I2C parts that have slightly different part numbers because the range of user-selectable addresses is different.
- xondono 6y ago
  For I2C addresses are hardcoded, with some chips leaving some bits to be set by hardware configuration. Far more interesting in that regard is the SMBus, that is compatible in most cases with I2C but can handle things like address resolution.

ashtonkem 6y ago

You can get around this with an I2C multiplexer[0]. It allows you to connect 8 devices to the multiplexer and then occupy one address on the main bud. 0 - https://www.adafruit.com/product/2717 https://www.adafruit.com/product/2717

fh973 6y ago

How is the allocation of addresses done typically? Are they always hardcoded? Is the same chip then available with different addresses (different SKU)?

aulin 6y ago
most common practice I've seen at least with typical arduino/rpi sensors is fixed address for the same chip, sometimes you can change one or two bits so you can have two/four of the same kind in the same bus, sometimes you have address conflicts with similar devices from the same manufacturer (e.g. bosch bme680, bme280 and bmp180).
pantalaimon 6y ago
Typically addresses are only 7 bit (10 bit are possible but not all devices support that). So you either have way to set the address using resistors / address lines or you have some config more where you set the configuration for the sensors one by one (Cypress touch sensors had this)
magicalhippo 6y ago
> Is the same chip then available with different addresses This is sometimes done, though more commonly in my experience is there are some input pins which the chip uses to determine the actual address. This might be as simple as one to three inputs which should be connected to ground or supply voltage to encode the last bits of the address. Other chips are a bit more creative, and allows you to, in addition to ground and supply, tie the address pins to the I2C clock and data pins. This allows it to generate four combinations from per address pin.
moftz 6y ago
People have already touched on setting the addresses using the pins but sometimes you can just buy near identical I2C parts that have slightly different part numbers because the range of user-selectable addresses is different.
xondono 6y ago
For I2C addresses are hardcoded, with some chips leaving some bits to be set by hardware configuration. Far more interesting in that regard is the SMBus, that is compatible in most cases with I2C but can handle things like address resolution.