Questions tagged [expander]

Questions regarding Port or IO Expanders, be it I2C, SPI, 1-Wire, serial/uart or similar. Shift-Registers are normally NOT considered Expanders, and have their own tag.

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Why are GPIO Expander Registers Being Rewritten?

I'm using an LPC1768 microcontroller (mbed) and 4 GPIO expanders (MCP23017). I am trying to write to the expanders to enable the pull up resistors and some other functions, but am getting strange ...
Nate.Olson's user avatar
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Does my GPIO Expander have a floating pin? [Button and pull-up resistor]

I am using GPIO expanders (MCP23017) for an array of buttons. Each button is connected between GND and an input pin of the expander. I've enabled the 100k internal pull-up resistor on the MCP23017 (...
Nate.Olson's user avatar
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2 answers
51 views

3.3v/5.0v selectable IO port expander

I have designed a basic IO port expander that has uses a bi-directional voltage translator in the hope to have a voltage selectable IO to an external device. Voltages are most likely to be 3.3v / 5.0v....
Aaron N.'s user avatar
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1 answer
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Two PCF8574 detected but not the third PCF8574

I'll be using an Arduino Nano 33 IoT together with three PCF8574 IO expander boards. I've managed to connect two PCF8574s together and communicate to each of them individually at different address ...
Arduino Rookie's user avatar
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1 answer
144 views

Using MAX7301 GPIO Expander for Raspberry Pi Switching and Chip Selecting

I'm designing a PCB that uses Analog Devices' MAX7301AAX GPIO Expander IC to expand the Raspberry PI's GPIOs. Digikey MAX7301 The reason I'm using this IC is that my application requires a lot of ...
Austin's user avatar
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1 answer
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Issues with I2C from MCP23017on Arduino

I am trying to use the MCP23017 expander chip with a Metro Mini by Adafruit (pinout below) and I can't get the microcontroller to connect reliably via I2C. update I connected the RESET pin to 5V and ...
Lil Mami Chula's user avatar
1 vote
1 answer
59 views

Confused by i/o expander datasheet note re internal pull-ups

The inputs on the NXP PCAL6524 i/o expander can be configured with internal pull-up or pull-down resistors. The datasheet states, "External resistors are required for inputs... that may float. If ...
Slothrop's user avatar
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379 views

24V I/O (PLC) to 3.3V interface with opto and PCF8574

I am more of a software guy, and I want to make sure my design works before sending it off to fabrication. I need to interface with 24V PLC I/Os. I want a simple design for now, as I can add ...
codecarbo's user avatar
1 vote
6 answers
493 views

Should I connect the base of a 5 V high-side PNP to a 3.3 V GPIO IC?

I'm trying to drive a 5V 200mA fan from a PCF8574 powered by 3.3 V. For context, I asked a separate question about using active low vs high on this expander, and @Justme recommended using a high-side ...
Nick Bolton's user avatar
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Is active HIGH or LOW preferred for driving loads with the PCF8574?

I'm switching a 5V 200mA case fan with a PCF8574. Since this expander is best used as a current sink (it can sink 25mA, but I think it can only supply something like 300uA), I supposed that a PNP ...
Nick Bolton's user avatar
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3 votes
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Is it advisable to current sink an LED sourced from 5V into a PCF8574 sourced from 3V3?

I'm using a PCF8574 to sink current from an LED. The PCF8574 VDD is 3V3, but the LED is sourcing from 5V. I think voltage drop on the LED is around 2V, so if I understand correctly, then the IO IC ...
Nick Bolton's user avatar
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5 votes
1 answer
526 views

Why does read from I2C GPIO Expander MCP23017 requires NACK

I'm using the MCP23017 16-bit I2C GPIO Expander in combination with the microcontroller PIC18F47J53. Both products are from Microchip. Datasheet MCP23017 Datasheet PIC18F47J53 I use MCC (MPLab Code ...
Hans Billiet's user avatar
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4 answers
133 views

I2C Strange goings on

I am using a Teensy 4.0 and an MCP23016 Port Expander (only I2C device) on my PCB. I have 4k7 pullups to 3V3 on SDA & SCK. SCK track is 77.9 mm long, 0.254 wide. SDA 64.3 mm long, 0.254 wide. I ...
smalljimmy's user avatar
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2 answers
202 views

Port expander with high side switch ground dilemma

I have a design wherein the basic idea is to control individual LED strings and dim (analog dimming) them using Pi Pico via I2C interface. This board is the LED driver which will be connected to the ...
JAGADISH K's user avatar
4 votes
3 answers
683 views

EEPROM with GPIO [closed]

Trying for a while now, but I cannot find an EEPROM memory with some address bit mapped to a GPIO. Or from a different angle, a GPIO expander with an EEPROM memory to save the config. Do such devices ...
Łukasz Przeniosło's user avatar
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1 answer
301 views

individual tri-state output IC with SPI / I2C / shift register input

Is there any simple non-MCU IC that allows switching several outputs (8 or more) tri-stated, eg. set any output to either high (~2V), low or open individually ? Input may be shift-register, SPI or I2C....
dronus's user avatar
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1 answer
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How do you configure the 74HC595 to have low pin outputs at power on?

So far I have somewhat successfully used a shift register (74HC595) and an output expander (PCF8574) to control FETs and BJTs. The main drawback so far seems to be that the chips I’m using have ...
Nick Bolton's user avatar
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498 views

Driving MFET with IO Expander ( mcp23008/mcp23017)

for my project I want to drive about 12 x IRLl014 FETs with an ESP32. To get more pins I want to put a IO-expander, either a MCP23017 or MC23008 onto the I2C and out onto the gate. I know that driving ...
Daniel Do's user avatar
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2 votes
2 answers
477 views

Daisy chain multiple PCB with an existing IDC cable

I'm not sure, if I just miss the obvious, but I'm stuck on seemingly simple problem and can't find a solution. I have a series of PCBs, I want to daisy chain. The number is between 8 and 12(max). The ...
KarlKarlsom's user avatar
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2 votes
0 answers
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Using an MCP23008 IC with a 4X4 matrix keypad on a Raspberry Pi [closed]

I want to be able to free up the native GPIO pins on my Raspberry Pi Zero. I know the MCP23008 gives me 8 extra pins, but I can't seem to find any resources on using the additional pins with a 4X4 ...
Pekkle Juice's user avatar
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Can I/O expanders be used to drive a Camera or LCD?

After searching around it seems that I/O expanders are used mostly to drive LEDs or buttons. Could something more complicated like an LCD be driven without bit banging? I.e. are there typically ...
JC2020's user avatar
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MCP23S17 - do I have to use both Chip Select and Hardware Addressing?

I've used MCP23S17 before. 6 of it and I just used Chip Select. Hardware address pins all 0. https://ww1.microchip.com/downloads/en/DeviceDoc/20001952C.pdf In datasheet, hardware addressing can be ...
Ariel Narboada's user avatar
1 vote
2 answers
2k views

Feedback schematic/pcb 16 channel relay wifi module

I have a few questions about a 16 channel relay module I designed, maybe someone can help me. Generally this consists of a ESP-12F, two I2C IO Expander, two darlington array ICs to drive 16x 5V relays....
Stackoverflowsuperbad's user avatar
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2 answers
610 views

74HC595 getting really hot on my pcb

I've designed a fairly simple circuit with some shift registers (3 output en 1 input). In the circuit, I've connected the inputs from the input shift register to pin connectors on the board (so I ...
oneindelijk's user avatar
0 votes
3 answers
324 views

Finding a I/O expander that supports 18 PWM outputs or another solution for MOSFET control

I am a student working on a university project. I need help figuring out how I can supply 18 PWM signals to 18 gate drivers, in a 3-phase inverter. The inverter is built up of 3 half bridges, with 6 ...
Eirik's user avatar
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1 answer
148 views

Does a Mcp23s17 output pin keep the value after being unselected?

I'm designing a SPI based communiations circuit between Raspberry Pi4+B as a master and (n x 8) GPIO expander modules, as slaves. Concretely we have selected an MCP23S17 GPIO expander: Datasheet By ...
Suvi_Eu's user avatar
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PCF8574 and OLED SSD1306 I2C conflict

I have a ESP12 module which is connected to multiple I2C devices such as an 24C08 EEPROM, DS1307 RTC and a PC8574 expander. Everything works fine until I decided to add an OLED module to this setup. ...
Mehdi Maazi's user avatar
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0 answers
422 views

Driving laser modules with MCP23017 and MOSFETs

I would like to make a PCB to switch 16 laser modules on and off. The laser module in question is this one: https://www.sparkfun.com/products/9906 I believe the module already has a driver included (...
Spatial Effects's user avatar
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1 answer
311 views

Use PCF8574 switch selection multiple SPI slave devices, is it possible?

My project use esp8266's SPI communicate with MCP3208 and SDCard, to select which device to be communicated, that device's CS pin need to set low, and set high to another device to disable, right? My ...
Ngô Hữu Nam's user avatar
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1 answer
204 views

Trouble with SO on MCP23S18 spi gpio expander

I am unable to get a signal out of the slave out (SO) line of an MCP23S18 For those not familiar it is a slave SPI gpio expander. Clocking in 32 bits, as it goes 16 bits set up, 8 bit opcode, 8 bit ...
axa's user avatar
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1 vote
2 answers
403 views

Is this a valid configuration for decoupling capacitors on an IC with two supply pins?

I have a project that's using an IC that only comes in SMD packages. With my limited soldering experience, I think I could potentially solder a TSSOP, but I think QFN is well beyond my capabilities. ...
D. Patrick's user avatar
1 vote
5 answers
2k views

Why are devices like the MCP23008 or PCF8574 still around when cheaper alternatives exist? [closed]

INB4: if this question doesn't fit this board, please delete. But I don't know where else to ask. There're plenty of I/O port expanders available. Most of them add 8 I/O lines at the cost of two I2C ...
Zhenek's user avatar
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3 votes
5 answers
4k views

UART expander (5 ports to 11 ports)

I have a board that I would like to design and there are 11 devices that can only be spoken to via UART. I am restricted to a Microchip uC chip product range and I have found one with 5 UART ports. I ...
Gareth T.'s user avatar
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1 vote
1 answer
216 views

Pull up/down a pin on a PCA9536 does not register?

Quite a obscure question here, concerning a very specific I2C expander IC, however I believe that this example can be replicated with most expander bus ICs. I am using a PCA9536 to switch the 4 pins ...
GeoReb's user avatar
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0 votes
3 answers
204 views

Volt/Amp dependent RLC band pass -> Loudspeaker expander using lightbulbs

I want to create a input energy dependent frequency shunt network, which goes in parallel with a loudspeaker, At low volumes, a certain midrange frequency should be shunted off the loudspeaker. The ...
maxbauer's user avatar
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2 answers
3k views

Wiring CJMCU-2317 MCP23017

I got the CJMCU-2317 MCP23017 I2C Serial Interface 16 bit I/O Expander Serial Module to use on a split keyboard as an extension matrix. This seems like an all-in-...
Issam Zoli's user avatar
2 votes
3 answers
684 views

Controlling 13 outputs with a mcp23017 or 74hc595 and two uln2003?

I need to drive 13 20ma (constant) loads with a single microcontroller with only 5 available pins. My first thought was to just use a mcp23017 or some 74hc595's but after reading the datasheets it ...
Ryan Detzel's user avatar
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2 answers
3k views

Multiple analog inputs on A0 pin (ESP nodemcu) with PCF8574

I am trying to read out several analog values on one analog input on the nodemcu. As sensors I am using two potentiometers which are connected to GND via a PCF8574 8-bit I/O expander. With the code ...
Lukas's user avatar
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1 answer
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Power supply issues with LCD and MPC23017 expander chips

I have an Arduino Uno and I'm working on a project that requires me to use six MCP23017 chips on a I2C bus plus a LCD 16x2 monitor. I need MCP23017 chips to power 36 LED's at the same time (8 LED's ...
Tevz's user avatar
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1 vote
1 answer
7k views

Are pull-up resistors needed when connecting buttons to a IO expander?

I'm connecting many momentary switches to a IO expander, like the MCP23017: . I read that I need to put pull-up resistors for each switch connected to the MCP23017. On another place (datasheet), I ...
Basj's user avatar
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0 votes
1 answer
782 views

Will continuously polling I2C port expander damage it or reduce its life?

I am using I2C port expanders namely TCA9554A and TCA6424A in my project. I have two options to read the inputs - (a) wait for interrupt and read (b) continuously keep polling the chip for any input ...
Whiskeyjack's user avatar
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1 vote
2 answers
374 views

Benefits of using an External A/D converter with ATmega128

I am new to electronics and working on my first project. Can someone explain why you would use an external A/D converter instead of the on board one? According to Mplabs the ATmega128 has a 8-...
Display Name's user avatar
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2 answers
199 views

How to expand a pulse by a factor

i have a read out ic of optical front end which gives out digital pulse(0-3.3V) of width 10ns to 150ns repeating at a rate of 1Hz-70KHz i have to measure the pulse width, but it needed a high end ...
kakeh's user avatar
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4 votes
2 answers
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MCP 23018/23S18 for LED and Switch control

I'm working on a project that involves about 200 LEDs and about 120 Switches. I'd like to use several MCP23S18 DIP chips across 2-3 buses to control everything. I'm a CS guy and just want to make sure ...
guyfleeman's user avatar
1 vote
2 answers
849 views

Should the reset pin on MCP23S17 go to a GPIO?

Most example schematics for Arduino, Raspberry Pi etc have the reset pin tied to GND. If number of GPIOs on the MCU wasn't a problem, would it be beneficial to have the reset of the expander ...
Newbie Noob's user avatar
1 vote
2 answers
810 views

Need to get more analog inputs Arduino Uno

Im making BattleShip on the Arduino: 2 x grid ((10x10 push buttons) + (10x10 led 5mm)) 2 x grid ((10x10 reed switches) + (10x10 led 5mm)) I made a 10x10 grid of push buttons by setting 10 buttons ...
Bart's user avatar
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1 answer
779 views

Will MCP23017-E/SP be compatible with an ATtiny85? ATmega328P?

I mainly want to also be able to use the same I/O expanders with ATTiny85 projects since those chips have limited pins. I will be doing the main prototyping on an ...
user avatar
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1 answer
209 views

SX1509 Analog to Digital Converter?

I purchased this product: https://www.sparkfun.com/products/11502 I've wired it up to 5 membrane pressure sensors which provide variable resistance depending on the pressure exerted. However I'm not ...
Dylan Vester's user avatar
3 votes
1 answer
893 views

How to read SAA1064 7-segment values

I have a central heating system that displays it's info and error codes on 4 7-segment displays. These displays are driven by a SAA1064, like so: This SAA1064 (datasheet here) receives it's ...
KJdev's user avatar
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1 vote
0 answers
304 views

MCP23017s and arduino problems

I'm not native English speaker, so forgive me my bads. Ok. Here's the deal. In my Arduino UNO I need more outputs and inputs. I bought 3 MCP23017s. One of them for receive states from 8 ...
Grzegorz's user avatar