I am working on IoT Technology, in my current project I want to connect two sensors like BMP280 and TSL 2561 by using Raspberry PI 2.
But these two sensors are using the Same I2C Bus Pins (I2C1 SDA and I2C1 SDL on the Raspberry PI2.
Please tell me how can I use the above two pins for two sensors.
-Kishore
Have you read the I2C protocol? I2C is kinda of a serial communication bus, and you can attack multiple slave devices to an I2C bus master.
In your case, just share the SDA and SDL pins on the raspberry pi, those two sensor are distinguished by the unique device IDs when you discuss with them.
Not to mention that you have different sensors(BMP280 and TSI 2561), the manufacture ID could be just enough for differentiation.
We could even attach multiple I2c slave devices to the same I2c bus, the way we differentiate them is to use different address(normally 3 address pins). However, the total number of slaves would be limited, up to 8 though.
Related
I have a Gateway - Node application using the LoRa module but I don't know whether to choose the LoRa module to interface UART or SPI.
Can someone help me distinguish the difference when using these two types? Example: when I have 5 Nodes connected to Gatewway, which one should I use? and same when I have 50 Nodes.
Thanks!
A UART converts the signals to RS232 signaling(NOT VOLTAGES, You will need an additional adapter chip like the FTDI 232H) to hook up to a serial port on a computer. Speeds are usually limited to less than 400 Kilobits per second(varies based on distance and devices)
If you are connecting multiple devices to the same micro-controller(Arduino), use SPI. The connection speeds are not limited by standards. It is a bus arrangement with 4 pins (clock SCLK, input MISO, output MOSI and Slave select SS) The SCLK, MISO, MOSI are connected to all devices.To chain additional devices it requires an additional SS pin per device.
SPI is going to be faster(several (<5?)Megabits per second is not uncommon (depends on length(not greater than .3 meters), wire quality, environmental noise and device specifications) and requires less discrete components.
Since LoRa speeds max out around 300kbps, a single SPI connected gateway could theoretically handle 15 LoRa transceivers on a single gateway.
Doing 15 devices may violate local RF duty cycle restrictions resulting in fines and/or imprisonment.
Please check with your regulatory institutions prior to implementation of any solution.
I would suggest using four transceivers with external antennas each pointing in a different cardinal direction(possibly offset) at each gateway. This configuration should permit 400+(depending on usage patterns) client devices per gateway.
I'm controlling a couple of i2c slaves (PCA9505) using the I2C module of National Instruments LabVIEW. I need to improve the project so I can add new slaves to the bus without manually adjusting the address of the slaves. (pins A0 A1 A2 on PCA9505). As a consequence, hardcoding the addresses is not a option.
Also, PCA has only 3 pins, so I can add max 8 slaves. I need to go for 16.
How can I give the slaves dynamic addresses?
How can I expand to 16 slaves?
Thanks for your help!
PS: PCA9505 = 40-bit parallel input/output (I/O) port expansion for I2C-bus applications
Personally, I like to use a configuration file to set the parameters needed for an application. In this case, it would define the addresses for each device you need to talk to. Arrays also help a lot here for expandability.
As far as extending your I2C bus, you can use something like a PCA9544A I2C mux. This chip allows for controlling 4 different buses. You will have to control the mux as part of your addressing of the individual chips.
From a brief read of the PCA9505 datasheet it doesn't look as if there's any way of selecting the device's address other than using those address lines. You are either going to have to multiplex the bus as crossrulz suggests, so that each device is at the same address on a different I2C bus, and add code to control which one you talk to at any one time, or add some hardware that sets the address lines differently for each device.
Will the devices be added to the bus via some sort of connector? If so could you include the address lines in the connector, so that each connector on the master adapter sets a different address for the device that's plugged in to it? Or if you connect devices in a daisy chain, each device could add 1 to the address on its upstream connector and output the new address on its downstream connector?
I'm looking to create a device that acts as a host to a USB peripheral, format the data, then send it out to another host (the PC). Are on-the-go chips capable of accomplishing this or would you need to implement both a host USB microcontroller and a peripheral USB controller? I don't see much information out there for creating a middleman that performs data molding for USB prior to reaching a host. Any information would be appreciated, hopefully I didn't butcher this concept.
you should use a microcontroller with 2 USB busses.
One should act as a host, and the other as a slave.
You will need to implement them both.
USB OTG is used to create a host and a slave in 1 device with 1 connector,
so it's impossible to use them together at the same time.
I have an old hub that sucks, so I converted it to a USB-tripler by soldering all of the input 4 wires to the corresponding wires on the output connectors. I had to do this because modern devices require 2.0 or 2.8 volts on d+, and refuse to charge if d+ is shortened or not connected. It works well charging three devices from a 1a wall adapter.
But if someone accidentally connects this to a PC port, what will happen? Well if there is only one device, it would be detected no problem. But if two devices are wired to the same port, how dangerous is that?
I would prefer the first connected device to be identified in the system, while the second connected devices just get the power.
One of the first steps in USB enumeration is to send a reset signal by driving D+ and D- low. All the devices plugged in will see the reset and think it was intended for them. After the reset they will each think they have address 0 and respond to requests to that address. The result will be multiple devices trying to drive the bus at the same time, for a brief period before the host gives up.
I think it wouldn't damage anything, but you will be causing a short circuit for a few microseconds which is bad.
I'm trying to interface the Mindwave (http://store.neurosky.com/products/mindwave-1) with my Altys board, through the USB UART port. The dongle I'm trying to connect is basically a wireless reciever that outputs serial data stream on the USB connection. I'm trying to read in this serial stream on the FPGA.
The problem I'm seeing is that when I try to Chipscope the UartRx pin (A16), I see no activity on it even though the dongle is supposed to send 0xAA in standby mode.
Since the FPGA does not power the dongle, I have it connected to an external power USB hub and then connect the hub to the FPGA. However I don't see any activity.
Do I need to convert the signals to another level, or invert them? I thought the EXAR chip takes care of it.
Did you try swapping RX and TX?
Did you have acces to a scope? To check you can repeatly send 'U's (0x55) and look with a scope to see which line is RX and which is TX. You can also check the speed of the interface with this method.