Does I2c Need Pull Up Resistors

Knowing I2C pretty well is required though. You need to have some pull-up resistors on the lines. The Promira platform when used as an I2C slave has 560 Ohm internal pull-up resistors that cannot be turned off. The I2C default state, the calm state during which nothing is happening, is called the Free State, and is noted as having both the SCL and SDA lines at logic high. The I/O circuit on pins 14 and 15 depends on how the pins are configured. Some designs CMOS-drive SCL for simplicity, (saves the SCL pull-up) but that is outside the formal i2c spec, and does not allow SCL clock stretching. The two resistors above are the pull-up resistors that allow the whole system to work - when all devices are inactive then the "pullups" pull the signal wire to the supply voltage. 8K pullups) but has had problems with clock stretching every since it was first introduced. 7K resistors and they worked fine. DS3231 Module Setup. 2-10 kilo-ohm resistors connected from both data and clock lines up to high logic level. 6k pull up resistors, but I am not sure how to represent it in the simulation. You only need one pair of resistors, not a pair for every module. Sometimes, an I2C slave device my hold the line low if it does not power-up correctly. 3V with some sort of level shift, this is likely to mean that you may need different pull up resistors to get them working. The documentation is so patchy. In our ESP32 story, do we need explicit external pull up resistors or is this taken care of for us by configuring I2C or do we need to explicitly define the mapped pins as pulled-up or some other story. In order to do I2C you're going to need something besides the FTDI chip. I am Bobby Wen. Does anyone know of an IC that acts as an active current source to pull-up the lines? I2C Active Pull-Up IC. I had no problems running it off of 3. The datasheet does not mention internal pull up or pull down resistance, so an unconnected pin might be a. Devices on the bus actively pull the lines low, but not high. Typically these are around 5K Ohms. 7k in our designs. VL53L0X -- maximum sensors on I2C arduino bus have onboard pull-up resistors, so you shouldn’t need external pull-ups, though adding them shouldn’t be a. If you look at the traces on the pc board, you see that they go to pins 1, 2, and 3 of a PCF8574. I'll install it and then view your document. Most Arduinos do not have pullups built-in. Thank you so much for the information. The maximum is 3 mA to meet the i2c specifications. The pullups take care of pulling it back up again. Therefore this topic shows ways to expand ADC pins in the micro controller. First question his about the two capacitor C75/76. The I/O Circuit for I2C Slave Configuration. i2c help need with pull up resistor problem The 8451 requires pull up resistors between the ranges. Mine uses a pair of 2. what is the purpose of these pullup and pulldown resistor and how to decide which resistor need. More confusing for a newbie like me, I see photos of projects on the web, where people are using chronodots RTCs with other 3. If devices were allowed to drive the bus HIGH, a collision on the bus could cause fried components. The Atmega328 is configured to use internal pull-up resistors which may be adequate for short cable runs. 7K to 10K ohms. I read that I need to use pull-up resistors to make this work, so I connected SDA and SCL to VCC with 2. We typically use 2. Waveform 1 represents turning off the I2C device, which will release the bus lines so that they can go HIGH. Hi all, I'm testing inputs on the pi and even when activating the pull-up resistors I get 100's of high/low changes per second. (I also tried to debug using a PICKit-3, but have. You need to add a resistor between each of SCL and +3. This is probably only a concern in battery powered low power apllications like a I2C realtime clock that should run for several months. Also, do I need to add pull-up resistors for the Beagle I2C/SPI Protocol Analyzer as well as the target device? Thanks for your questions! The Beagle I2C/SPI Protocol Analyzer provides built-in resistors, and you have the option to power the target device with the Beagle analyzer's power source or an external source. My signal wires are 3/4" to 1" long with farite beads on them with 10k ohm pull up resistors from the I2C 5v to each of the signal wires. Software configurable I2C pull-up resistors. Of course if any of the devices have built-in pullup resistors you can omit the external resistors. The resistor is 33 ohms because it's small enough to not form a voltage divider with the pull-up resistor to affect the voltage thresholds of the I2C signal, but is still enough to protect the device from current surges in the I2C lines (which may be long). This is probably far too slow for an I2C - particularly if you are planning to run it at 400kHz - the rise time should be less than 300ns So you probably do need an external resistor for the I2C pull-up. Remember though that if other I2C devices are added to the bus they must have their pull-up resistors removed. Creating, debugging both SDA and SCL need pull-up resistors. Here we can't work with a simpe voltage divider, we need a level shifter. Re: PN532 RFID Breakout Board - I2C Pull-up resistors by mlmyrick on Sat Jan 20, 2018 4:58 pm So to be clear, do I understand correctly that (a) the documentation for the PN532 breakout board current in January 2018 is for an older version of the breakout?. Figure 6: I2C diagram Assembly of Components 4 connections are needed for the connection between the IMU and Arduino. So, it's just adding two resistors. You merely have to ensure the resistor is low enough in value to achieve the speeds and capacitive load in your system. Exploring a digital I2C/SPI accelerometer (MMA7456L) with Bus Pirate Posted on February 20, 2010 June 15, 2011 by starlino Bus Pirate is a great tool for exploring new chips using your PC , without the need to integrate the chip into a MCU project. 3V, although it may have shared the i2c bus with another sensor that probably had 10k pull-up resistor. Are you aware that both the SDA data line AND the SCL clock line are both bidirectional lines? That is why they both use pull up resistors. I have pull up resistors in place, but after watching this video again, I noticed what will hopefully be my. I 2 C is a fairly robust protocol, and can be used with short runs of wire (2-3m). I2C−Bus Systems As with the standard I2C−bus system, pull−up resistors are. When using the wire library (for I2C in Arduino) it activates internal pull-up resistors (20k-150k, depending on the pin and the board model) and Mega 2560 board has on board pull up resistors (10k). I'd like to be the first one in my building to debug this board, if someone can give me some suggestions of what else I should look for. The SCL/SDA controlling fans out to four downstream channels. It's time to move beyond! In this post, we will discuss all the theoretical concepts that you need to know regarding I2C before programming/testing it on real devices. The I2C default state, the calm state during which nothing is happening, is called the Free State, and is noted as having both the SCL and SDA lines at logic high. I2C requires pull up resistors on the SCL+SDA pins. The MSP430G2553 spec says that there are internal pullup/pull down resistors available on Port 1. Because pressure changes with altitude you can also use it as an altimeter! The sensor is soldered onto a PCB with a 3. First, the pull-up resistor must limit the current to a level that does not exceed the maximum drain current of the output transistor. 03 hPa resolution so we don't suggest it as a precision altimeter. But I think one can do it when using a PIC as a slave through its (M)SSP. When it is not connected to a I2C protocol bus, the pin floats in a high impedance state. When connecting the USB-to-I2C Basic to user a user target system, a minimum of three (3) wires will be required. The value of the pullup resistor is an important design consideration for I2C systems as an incorrect value can lead to signal loss. I have seen anything from 1k8 (1800 ohms) to 47k (47000 ohms) used. 7K on both the SCL and SDA lines. Circuit with current. You need to add a resistor between each of SCL and +3. 60 1 x TIP120 mosfet or other 5v compatible €0. Rp commonly ranges from 1 kΩ to 10 kΩ, resulting in typical pull-up currents of about 1 mA and less. Also, you state your sensor needs between 4. MEGA 2560 board has pull-up resistors on pins 20 - 21 onboard. You will need to check. For the line to be able to go high you must provide pull-up resistors to the 5v supply. 3V and SDA and +3. Software configurable target power pins to power downstream devices. 8k (they will draw ~1. 7k will be fine, for higher frequencies and longer lines things can get more complicated. You only need one pair of resistors, not a pair for every module. For I2C, you will need to add external resistors of 1k (very strong) to 10k. 7K to 10K pull-ups on both the SDA and SCL lines. That's the role of pullup resistors. An application of a pull-up resistor is attaching a button to an input pin. They are calculated as a function of bus capacitance (number of devices, trace length) , supply voltage and input curent. Pull up resistors The MOD-1016G comes with no pull up resistors I2C The board comes pre-configured to use I2C. Design the Pull up resistors in such a way that the current through the internal clamping diodes is less than 5mA. I learned the hard way. Calculating Pull-up Resistor Value. The pull up resistors still need to be connected between power and scl and sda of your device. All these do is ensure that between bits, and between transfers in general, these two wires are kept around VCC, making them a logical HIGH value. For more information on pull-up or pull-down resistors see this article. If that is the case than you probably do not need to add any more. The pullup resistors needed to get the module to start up correctly can double as the I2C bus pull-up resistors and the other, slave, component. 5 V tolerant! How to Use. Arduino Uno board has I2C pin shown in. The Expander Pi and Servo Pi should work together on the same I2C bus. For the line to be able to go high you must provide pull-up resistors to the 5v supply. begin(9600); Next, initialize digital pin 2 as an input with the internal pull-up resistor enabled: pinMode(2,INPUT_PULLUP);. Since the lines can only be driven low you should use S0D1. i2c is a bidirectional bus. The GPIO0 and GPIO2 determine what mode the module starts up in and the TX/RX pins are used to program the module and for Serial I/O, commonly used for debugging. 3 After extensive debugging and studying the drive's complex head movement control system, we. We can easily interface the real time clock DS1307 with PIC Microcontroller by using the built in Library functions of MikroC compiler. If you need to supply power to your I2C slave device (up to 50mA), you can select either 5V or 3. The hostname in the URI is ignored, if specified. I2C needs pull-up resistors. 7k pull-ups on SDA and SCL pins to 5v, but @dgordon42 says the Pi already comes with 1. So if using the I2C pins, then the “safety” resistor needs to be much smaller, but when using the other pins then 10K is fine when you enable the internal. Mine uses a pair of 2. Getting around 2V on both the pins. Re: PN532 RFID Breakout Board - I2C Pull-up resistors by mlmyrick on Sat Jan 20, 2018 4:58 pm So to be clear, do I understand correctly that (a) the documentation for the PN532 breakout board current in January 2018 is for an older version of the breakout?. Does anyone know, does the F3FC tricopter board already have pull-up resistors mounted on the I2C bus for the internal barometer?. Though AVR Microcontrollers have internal pull ups which are automatically enabled by the Wire. When enabling the I2C port it seems both ports are enabled - is it possible to only enable 1 port and use the other I2C port as IO pins? Our assumption in Raspbian. This makes sense as they are in that state by default due to the pull up resistors. The size of these pull-up resistors depends on the system, but each side of the repeater must have a pull-up resistor. In both cases, the button has no resistance (or at least, less resistance), and so when the circuit is closed it short-circuits around the pull up or pull down resistor and reads the other value. 76 volts before falling back to zero. I2C requires pull up resistors on the SCL+SDA pins. The port is an unsigned integer indicating which I2C port to use. Pins "SDA1" and "SCL1" does NOT have pull-up resistors on board. The I2C pull-up resistors definitely have an impact on the system. Pull-ups are common on most input logic lines, two-wire (I2C) lines, reset lines, et al. The pull up resistors can be useful when interfacing a 5V microcontroller to a 3V3 sensor as the pull up resistor can be connected to 3V3 to eliminate the need for voltage level shifting. The pull-up resistors must be reduced in size, when increasing the bus speed or when there is significant bus capacitance. An I2C interface MUST have pull-up resistors. If your application has an I2C bus that has pull up resistors already you can omit R2 and R3. Common question that comes up about pull-up resistors: what value do you pick and why not just use a piece of wire? In this follow-up electronics tutorial, the bald engineer looks at how to pick. Pull-down resistors work in the same manner as pull-up resistors, except that they pull the pin to a logical low value. I have pull up resistors in place, but after watching this video again, I noticed what will hopefully be my. The best trick to get extra inputs into the ESP8266-01 is to use an I2C interface. What is the I2C termination? I2C is required to terminate, so the line is free to add other devices. actually have pull-ups on the EHS6 or not). There should be a resistor from the SCL line to the 5v line and another from the SDA line to the 5v line. I have seen many a young engineer struggle with unreliable I2C communication due to either the entire lack of or incorrect pull-up resistors. Yes, TS3AUSB221 does not have internal pull ups. tinyLiDAR is controlled by any standard I2C host that can support clock stretching. If you face a situation, that the device works at low speed, bit not at high speed, add external pull-up resistors. (They "pull" the voltage "up", hence pull-up). Repeated Start, 10-bit slave addressing, and Combined Format transactions. The SDA, SCL, and GND on the USB-to-I2C Basic hardware must be connected to their corresponding signals on the target. Inter-Integrated Circuits - I2C Basics. In this project, we will show how to wire up a pull up resistor to a circuit. 7K resistor each). Rp commonly ranges from 1 kΩ to 10 kΩ, resulting in typical pull-up currents of about 1 mA and less. VL53L0X -- maximum sensors on I2C arduino bus have onboard pull-up resistors, so you shouldn’t need external pull-ups, though adding them shouldn’t be a. Figure 7: Pull-up resistors. That is if you connect to the Pi! But!! If you ever make your own I2C bus you must add pull-up resistors. Most of the I2C PCBs available have pull-ups in the range of 4. The typical value is 4. 3V with some sort of level shift, this is likely to mean that you may need different pull up resistors to get them working. 3-volt power rail, so we can connect both devices (if we connect other I2C devices to the bus, they must have their pull-up resistors removed. If you forgot to attach external pull up resistors you might get away with the internal pull-ups, but I wouldn't recommend it. There should be a resistor from the SCL line to the 5v line and another from the SDA line to the 5v line. 2 Configuration & Setup 1) The MAX17061 board provides locations for pull-up resistors on the SCL and SDA signals. This must be done in case that the master doesn't have these resistors and must be enabled only one I2C Encoder V2 in a chain. seem to show up when you search for Phillips I2C. Warning: for multiple I2C devices, or longer cable runs, the 4. Pull-up and pull-down resistors are used in I2C protocol bus, wherein the pull-up resistors are used to allow a single pin to act as an I/P or O/P. I2C communication, enables internal pull-up resistors by default. First you need to make sure the sensor is power on. 7k will be fine, for higher frequencies and longer lines things can get more complicated. There should be a resistor from the SCL line to the 5v line and another from the SDA line to the 5v line. There is a trick you can use. In high-speed circuits, a large pull-up resistor can sometimes limit the speed at which the pin can reliably change state. 7kΩ resistors are used. 7K resistor each). You can then use 10k resistors for a pull ups. This is probably only a concern in battery powered low power apllications like a I2C realtime clock that should run for several months. I wanted to use 10K resistors for both lines, and will connect RTC chip (DS3231SN) by default on the PCB board. Rp commonly ranges from 1 kΩ to 10 kΩ, resulting in typical pull-up currents of about 1 mA and less. at 100kHz (the standard I2C) frequency, it would take a lot of wiring to add significant capacitance if you use the common 10K value for the pull-up resistors. If your module does not include these resistors, install them on your breadboard between +5V and SDA/SCL. The I2C from the MC9S08QE32CFT is connected, as well as the SPI. The USB-8451 does not have the built-in pull up resistor. 1x Lithium 3. The options for the I2C protocol depend on the underlying device-specific I2C protocol used, but these options have been standardized for consistency. 3 votl power rail, so we can connect both devices (if we connect other i2c devices to the bus they must have their pull-up resistors removed) Thats all we need to connect our Raspberry pi to our Arduino board. Because you are a beginner I want to make sure you understand that although all of the prior posts are correct, there is no need to "match" the pull-up resistor to a certain number of I2C peripherals of certain speeds. If pull-up or pull-down resistors are needed for stabilizing floating input signals on a header pin, the user would need to include these in the external circuit connected to the UP board. Finally you would just need to include some pull-up resistors (about 10K) between the lines and the voltage source. Does that sound right? Maybe put weak pull-ups between the source and the AVR like this to ensure the FET will actually turn on. Generally if you use an I2C breakout it is part of the breakout. 6V rechargeable lithium cell button battery €0. Both have pairs of pull-up resistors. I2C bus is popular because it is simple to use, there can be more than one master, only upper bus speed is defined and only two wires with pull-up resistors are needed to connect almost unlimited number of I2C devices. First, the pull-up resistor must limit the current to a level that does not exceed the maximum drain current of the output transistor. You need 2, one between VCC and SCL, the other between VCC and SDA. So if NXP specified these I2C pins are "compliant with the I2C spec" this means they are only compliant with a 3. 03 hPa resolution so we don't suggest it as a precision altimeter. Because there is no pull-up resistors in the Arduino and because 3. void pullUpDnControl (int pin, int pud) ; This sets the pull-up or pull-down resistor mode on the given pin, which should be set as an input. The Raspberry Pi has them on one of the i2c buses. There is no requirement of a pull-up resistor in case of the SPI. I2C bus drives can pull signal lines to ground but they are not capable of driving it to high. Generally, the smaller the pull-up resistor, the faster is the rise of the signal to 1 , but when driving a 0 , there is also higher consumption. Board has A0-A2 with solder pads like (|). If you are using a different way to drive the display, make sure you install pull-up resistors for the I2C bus. 3V with some sort of level shift, this is likely to mean that you may need different pull up resistors to get them working. I presume the i2c pins is in a low state when released. I replaced the 3. But I'm pretty sure I tested first w/o anything else connected. The pull-up resistors are the block marked in red on the left. Instead of having outputs that can pull up and down, and open drain outputs can only pull down. This is the first thing that I suspect is giving you troubles. 3V the total pull-up must not be less than 660 Ohms. The datasheet does not mention internal pull up or pull down resistance, so an unconnected pin might be a. 7k will be fine, for higher frequencies and longer lines things can get more complicated. Some I2C devices have the pull up resistors built in so as to avoid external components. As discussed in the I2C Basics module, the resistors that are commonly seen on I2C circuits sitting between the SCL and SDA lines and the voltage source are called pull up resistors. The resistor values span the range from 250 to 50K ohms. 1, it was possible to configure the internal pull-ups in the following manner:. Warning: for multiple I2C devices, or longer cable runs, the 4. ** I2C communications require a pull-up resistor on both the SCL and SDA lines. If that is the case than you probably do not need to add any more. The timing diagram for the I2C is shown in Figure 3. Pull-up resistors are very common when using microcontrollers (MCUs) or any digital logic device. An example of a pull-down resistor in a digital circuit can be seen in the figure. I2C communication, enables internal pull-up resistors by default. For correct operation, SDA and SCL lines require pull-up resistors. This means that the bus drives the signals to GND, so they will need to be pulled up with a connection to some DC voltage. Each signal line has a pull-up resistor on it, to restore the signal to high when no device is asserting it low. - CAM_I2C is designed to tolerate 3. pick the value of pull-up resistors on SideB of the bus such that all devices on that bus can drive lower than VILB=0. 1, it was possible to configure the internal pull-ups in the following manner:. Resistor selection varies with devices on the bus, but a good rule of thumb is to start with 4. All these do is ensure that between bits, and between transfers in general, these two wires are kept around VCC, making them a logical HIGH value. The pull-up resistors are the block marked in red on the left. Figure 6: I2C diagram Assembly of Components 4 connections are needed for the connection between the IMU and Arduino. 7K to 10K pull-ups on both the SDA and SCL lines. Understand what is meant by bus capacitance and how pull up resistors interact with it. VL53L0X -- maximum sensors on I2C arduino bus have onboard pull-up resistors, so you shouldn’t need external pull-ups, though adding them shouldn’t be a. Also generally for messing around with breadboarding something running on I2C you can do without the pull-ups since the Arduino employs built-in pull-up resistors that. Theory of Operation. 7K Ohm pull-up resistors connecting the SDA and SCL lines to Vcc: Advantages and Disadvantages of I2C There is a lot to I2C that might make it sound complicated compared to other protocols, but there are some good reasons why you may or may not want to use I2C to. You are receiving this because you commented. You will probably need some pull up resistors, since I am not sure if the pull up strength of the MC9S08QE32CFT is sufficient for I2C recommendations. Pull-up resistor R2 thus pulls the output all the way up to 12 V when the buffer outputs a "1", providing enough voltage to turn the power MOSFET all the way on and actuate the relay. The great strength of I2C is that you can put so many sensors on the same four wires. Hi all, I'm testing inputs on the pi and even when activating the pull-up resistors I get 100's of high/low changes per second. 7kΩ, 1MHz I2C with 2kΩ). The pull up resistors are needed to pull the long transfer lines. A pull-up or pull-down resistor are used on input pins to define a state in the case an input does not have anything connected or the connected part is in the high impedance (Z) state. I did not try, but I am wondering if we really need to add external pull-up resistors at the SDA and SCL lines due to the fact that we have now two I2C devices. I am having trouble running an I2C scanner and reading the Chirp!. Instrument Control Toolbox™ I2C support lets you open connections with individual chips and to read and write over the connections to individual chips using either an Aardvark host adaptor or a NI-845x adaptor board. I think the problem is that the I2C bus need for pull-ups is not defined in terms of resistance but in terms of rise-time: a short bus with low capacitance can do with large values, but a looong one needs smaller ones, as long as you don't overstress the open-drain (open-collector) drivers. Bi-directional level shifter for I²C-bus and other systems. Thanks for the response. The resistors are completely the wrong value, being around 10- to 20-times too large. Turn out the pull-up resistors' value, both internal and external, was the main issue. Programs need to be linked with -lwiringPi as usual. 3V operated I2C peripheral to CAM_I2C. If power consumption has to be low, then use slowest speed you can and use highest possible pull-up resistor that your bus capacitance allows. GPIO0 and GPIO2 need to have pull-up resistors connected to ensure the module starts up correctly. TCS34715 Breakout board with decoupling capacitors and pull up resistor for I2C bus. Some I2C devices have the pull up resistors built in so as to avoid external components. The timing diagram for the I2C is shown in Figure 3. 7k pull-ups on SDA and SCL pins to 5v, but @dgordon42 says the Pi already comes with 1. The lower-value resistors cause increased current draw, as each logical low on the bus creates a path to ground, negatively impacting power consumption. I2C Pull Up Resistors. The I2C bus pins are a “open drain” lines. If it is combined with other sensor board which have also pull-up resistors, the total pull-up impedance might be too low. These pins may require pull-up resistors (that is, connect them to +5v via something like a 4. So if NXP specified these I2C pins are "compliant with the I2C spec" this means they are only compliant with a 3. On the other hand a high termination bares a potential risk of damaging components. Yes pull up resistors of 10 kohm each are present on SCL and SDA pins. I2C signals should be placed in a cable such that they have as little capacitance as possible to aggressor signals, i. 7K ohm resistors. You can now schedule the advanced functional tests from HLK manager. I2C bus signals master slave. Is this true? If so how do you use the API to to configure an I2C port without pullups? If pullup resistors are needed for I2C on LPC1768 what value of resistors and what the circuit look like on the pins?. The reason it works, is that the devices using it have open-collector drivers, and pull-up resistors to the power supply rail. The I2C bus is an open collector bus. In water I get about 150kohm of resistance. Calculating Pull-up Resistor Value. The side effect of this is that something needs to pull the bus high, otherwise it will float to random values. All I/O terminals are 5. The I2C Encoder V2 has I2C pull-up resistors, by default they are not soldered. This must be done in case that the master doesn't have these resistors and must be enabled only one I2C Encoder V2 in a chain. Are you putting 3. The bus slowly comes up to 5 volts due to RC constant of the pull-up resistor R1 and the parasitic capacitance of the bus line Cp. I 2 C is a fairly robust protocol, and can be used with short runs of wire (2-3m). 2016: This article which started off discussing the “new addition” of i2c to the home control software, is now NOT ONLY about an I2c 2/4 line LCD display facility recently added to the ESP8266 boards – but there’s a PARALLEL version as well, making use of GPIO 4,5,12,13,15 and 16. 7K ohm resistors. The maximum is 3 mA to meet the i2c specifications. Mine uses a pair of 2. Normally, you do need pull-up resistors for I2C (afaik), especially if the sensor doesn't already have them internally, so leave that in your setup. Another sensor for compass is standard I2C interface. The I2C default state, the calm state during which nothing is happening, is called the Free State, and is noted as having both the SCL and SDA lines at logic high. There should be a resistor from the SCL line to the 5v line and another from the SDA line to the 5v line. We can easily interface the real time clock DS1307 with PIC Microcontroller by using the built in Library functions of MikroC compiler. I had lots of trouble to communicate through I2C with my Arduino Mega2560. Some time ago I created a weather station using a Raspberry PI and an off the shelf weather station, connecting the two via USB. The I/O Circuit for SPI Configuration. But the HDC1000. 7k will be fine, for higher frequencies and longer lines things can get more complicated. For correct operation, SDA and SCL lines require pull-up resistors. Hello, I understand how pull-up and pull-down resistors work, but I fail to understand how they are always necessary. 1st question: about Due TWI1 pins (2nd i2c port): are there integrated pullups on-board or not? Pins "SDA" and "SCL" (number 20 and 21) have pull-up resistor on board. 7k ohm pull up resistors from VCC attached to the SDA and SCL lines. I don't know about the axi_iic block, but because the pmod_bridge sits between it and the output port I don't believe that the axi_iic block would configure the output ports to have pull-ups either. I am Bobby Wen. I don't know why you think the "I2C pull-up resistors need to altered". But the HDC1000. So besides all ambiguousities of terms, the question is rather clear and has been clearly answered by several contributors. So, it's just adding two resistors. Here, the low voltage input, ADIN, is used to measure the 5V output of the converter, while a direct I2C connection is made to the microprocessor. The Servo Pi uses 10K pull-up resistors for both the 5V and 3. It doesn't teach you that you need pull-up resistors, and 2. If I2C bus is powered from your hardware, the voltage can be any in the range from 2. I think he means adding the pull-up resistors. 7K to 10K ohms. An I2C interface MUST have pull-up resistors. When it is not connected to a I2C protocol bus, the pin floats in a high impedance state. But what is a pull up resistor? A pull up resistor is used to provide a default state for a signal line or general purpose input/ouput (GPIO. Theory of Operation. In both cases, the button has no resistance (or at least, less resistance), and so when the circuit is closed it short-circuits around the pull up or pull down resistor and reads the other value. I2C needs external pull-up resistors. The maximum clock frequency specified by the I2C standard is 1MHz. i2c help need with pull up resistor problem The 8451 requires pull up resistors between the ranges. Every I/O pin can be configured as either input or output, and can be individually read or written to. The specification does not list a lowest resistance that can be used. All any I2C master/slave can do is to abide by the specifications (and not screw up the bus for other devices!). Well, as you might be suspecting by now, one of the main problems caused by connecting multiple breakout board on the I2C boards is caused by pull-up resistors. Devices transmitting on the bus do so by pulling the line low. At the local end close to the Raspberry you'll need to set up a similar setup that reverse the line drivers SLC and SDA to local I2C but signals SLC and SDA that connects to the I2C on the Raspberry. I had lots of trouble to communicate through I2C with my Arduino Mega2560. This is how I think it would look using the internal pull up resistor. 1st question: about Due TWI1 pins (2nd i2c port): are there integrated pullups on-board or not? Pins "SDA" and "SCL" (number 20 and 21) have pull-up resistor on board. 2K (red/red/red) resistors. There should be a resistor from the SCL line to the 5v line and another from the SDA line to the 5v line. You need just one pair of resistors for the whole bus. I replaced the 3. An I2C interface MUST have pull-up resistors. I read that I need to use pull-up resistors to make this work, so I connected SDA and SCL to VCC with 2. This signals the MCU to poll the part to see what is going on.