The LTC4316 is article special. It’s an I²C abode translator that changes the abode of a accessory that would contrarily battle with addition on the aforementioned I²C bus. Not a hack? Not so fast. Absolutely how this dent does this ambush is able abundant that I couldn’t abide giving it the column it appropriately deserves.
What’s so special? This dent translates the abode on-the-fly, authoritative it cellophane to the I²C protocol. Up until this point, our best bet for complete abode collisions was to put the clashing dent on a abstracted I²C bus that could be selectively enabled or disabled. In that department, there’s the PCA9543 and PCA9547 demultiplexers which we’ve apparent before. Both of these accessories about act like one-way analysis valves. To abode any accessories downstream, we charge aboriginal abode the multiplexer and baddest the agnate bus. While these chips dness our abode blow problems, and while there’s technically a way to abode a very ample cardinal of devices if we’re not time-constrained, the ascendancy argumentation bare to address assorted bus base can get bulky for nested demultiplexers.
What’s so chic about the LTC4316 is that is preservers artlessness by befitting all accessories on the aforementioned bus. It prevents us from accepting to abode a complicated software accepted to abode assorted sections of a demultiplexed I²C bus. In a nutshell, by actuality protocol-transparent, the LTC4316 keeps our I²C master’s ascendancy argumentation simple.
I mocked up a quick analysis bureaucracy to accept a go at this dent in complete life.
The LTC4316 sits average our address-clashing accessory and the blow of the I²C bus, acting as a acting analysis valve. Aback an abode is beatific forth the line, it’s translated in-flight to the “private” SDA band that the address-clashing accessory sees.
Once all seven abode $.25 accept aureate by, the private SDA band is anon reconnected to the arrangement I²C bus (no added analysis valve) such that the address-clashing accessory can acknowledgment with an ACKnowledge if it was called by the bus master. If it was selected, chat gain as accustomed until the end of the transmission, at which point the private SDA band is broken again to bureaucracy for the aing I²C transmission. As for aback this abstract happens exactly, the datasheet doesn’t specify, although I doubtable it’s anon afterwards the I²C manual finishes.
Setting the adapted abode is a amount of spec-ing the appropriate voltages at the pins XORL and XORH. anniversary voltage dictates the high three and lower four translation $.25 for the accessories centralized XOR logic. To actuate the exact adaptation byte we want, we chase two steps. Aboriginal amount out what abode we’d like our arrangement bus to use to allocution to the address-clashing device. Again we charge to apperceive the address-clashing device’s absence address. With those two addresses, we again chase the equation:
…which agency we charge to accomplish the changed XOR to get our adaptation byte. Luckily, the changed operation of XOR is XOR, so we aloof charge to solve:
Phew–that’s not too tricky.
To set the appropriate voltages, the datasheet recommends a voltage divider. At aboriginal glance, this advantage seems somewhat power-inefficient. Luckily, the datasheet suggests resistors in the 100 kilohm range, which should be acceptable abundant for all but the tightest of ability constraints.
Following an abode translation, there’s a slight adventitious for the SDA band to “glitch” and discharge out one added argumentation HIGH voltage akin for a abrupt moment (shown above).
This affair is accurate in the datasheet’s “glitch” section. Luckily, it’s no dealbreaker. Because SDA abstracts is alone apprehend afterward the ascent bend of the SCL alarm line, this added passes through undetected. As for area this annihilate comes from, the datasheet doesn’t say explicitly. Nevertheless, I accept a anticipation that this annihilate coincides with the the LTC4316 disconnecting it’s XOR ambit and reconnecting the clandestine SDA band aback to the arrangement SDA line.
I²C has been about for over 30 years, but the LTC4316 has alone afresh alone assimilate our breadboards in 2015. Why such a huge adjournment for a dent that seems so useful? There’s no bright acknowledgment here, but here’s my best guess….
I²C was originally developed by Philips (now NXP) as a low-speed agreement for pin-constrained accessories primarily active in customer electronics (PDF). The mindset actuality was that bulk of customer accessories had agnate interfaces (lcd displays, on panels, etc.) that could be handled by a committed accessory which could again acquaint their after-effects abroad aloft request. This abstraction is modularity at it’s finest. Here, complicated functionality is handled by a committed device, absolution up the amount of the primary controller.
The I²C accessory portfolio has back developed to accomodate hundreds of new devices. In best cases though, if we can anticipate of absent to use one or added copies of any given device in one system, the architect has about absolutely enabled some way of configuring one or added of the devices address bits. Actuality lies the aboriginal acumen why we wouldn’t see an abode translator dent appear for so long: the architect has acceptable already predicted our needs and made abode alteration a affection that’s congenital into the device. Appetite to use one or two added PCA9685 sixteen-way LED drivers? No problem. Aloof toggle one of the six available abode pins. Does your BMA180 accelerometer abode affray with addition I²C accessory address? No sweat. Aloof tie pin 1 to argumentation LOW or argumentation HIGH to bandy the abode to the alternate.
Next off, for cases area we would appetite to handle assorted copies of a device, there’s already a drop-in solution: putting that accessory on an abandoned bus as we discussed earlier. Yes, there’s a bang in software complexity, but unless we’re acclamation nested levels of bus demultiplexers, the software charcoal adequately simple. In that sense, why change the I²C abode aback you can aloof bang the clashing accessory to addition bus?
In my mind, the better appliance of I²C abode adaptation may be for repurposing smartphone MEMs sensors. Sensors like the BNO055 IMU or the VL530X complete ambit sensor may accept a additional activity in the robotics apple in ample arrays. Given that these are addresses are fixed, a translator may accept it’s aboriginal use-case appropriate here.
As for the applied use of this dent in general, who knows? Nevertheless, aback the day comes that an abode adaptation avalanche beneath into our sights, we’ll be armed to handle it.
11 Things You Should Know About Brady Label Maker Bmp11 Plus | Brady Label Maker Bmp11 Plus – brady label maker bmp21 plus
| Encouraged to be able to my own weblog, in this time I am going to explain to you regarding brady label maker bmp21 plus