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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10 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 ...
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1answer
36 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 ...
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2answers
139 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. ...
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5answers
248 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 ...
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4answers
316 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 ...
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1answer
100 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 ...
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3answers
110 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 ...
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1answer
880 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-...
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3answers
261 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 ...
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2answers
2k 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 ...
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1answer
63 views

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 ...
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1answer
2k 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 ...
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1answer
379 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 ...
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2answers
156 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-...
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2answers
115 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 ...
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2answers
728 views

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 ...
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2answers
483 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 ...
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2answers
658 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 ...
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1answer
596 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 ...
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1answer
101 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 ...
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1answer
670 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 ...
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0answers
253 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 ...
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3answers
863 views

Do you always need a GPIO expansion chip when using i2c?

SUMMARY: I'm trying to learn the basics of understanding how to wire up a simple circuit using the i2c. I'm wanting to build just a simple project involving an LED and a push button with my raspberry ...
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1answer
388 views

MCP23017 in series

I have a hand full of MCP23017 (16 bit multiplexers/ I/O Expander) but I can only get 8 IC on the bus due to the limit of address but I need 200 pins (about 13 ICs) for a 8*8*8 RGB cube and was ...
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3answers
409 views

Increase GPIO outputs

I'm working on a project in which I need 32 outputs from an MCU that only has 8 free outputs. To accomplish my goal I have the following requirements: I must be able to toggle more than one output ...
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1answer
2k views

i2c over gpio - level shifter

I'm quite new to this. I have just basic background in electronics. So I would appreciate an advice from someone more experienced. I would like to connect an i2c display to my tp-link wr703n (ar9331) ...
2
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1answer
1k views

Issue controlling MAX7301 GPIO Expander via SPI using Arduino Uno R3

I'm trying to write a driver to control a MAX7301 GPIO port expander that will be controlled via SPI. I've used SPI before and it's pretty simple, but I've been working on this for a few days and I ...
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2answers
2k views

Problem with transmitting data from PIC18F45K20 (C18) to MCP23017

I am currently testing the MCP23017 (slave device) 16 bit I/O Expander using a PIC18F45K20 with the C18 compiler to transmit data to the MCP23017. The address pins (A0, A1 and A2) of the MCP23017 are ...
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2answers
139 views

A 4.8v reading on a loose pin 0?

I have a setup that demands that I use all my I/O's on my Arduino Uno R3 board - including the serial pins 0 and 1. So I've initialized those pins as inputs, but when I make a reading on pin 0 it ...
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1answer
526 views

How do I connect non-I2C devices to an I2C bus?

I'm quite new to electronics and just trying to do my first Raspberry Pi based system: one diode, one pressure sensor and LCD 1602 with keypad shield (the one for an Arduino board). The way I'd like ...
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2answers
4k views

Interfacing a MCP23S17 (SPI) with a FPGA

I am working with a MCP23S17 SPI I/O expander chip in a VHDL project on my Basys 2. At first glance I thought this was just a simple SPI interface where I put the chip select low and it will give me ...
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2answers
524 views

Multiplex two I2C ICs into four 7 Segment displays

I currently have two PCF8574AN I2C 8-bit IO expander ICs. Is there a way I could have two seven segments be driven off one IC (So i could run four seven segments displays off the two ICs that I have). ...
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1answer
1k views

PIC, SPI problem with SD card and other devices

I'm using a PIC24H as a master connected with a microSD card, ENC28J60 and a MCP28S08 port expander. I'm using the FatFs library for a microSD card and the Microchip TCP/IP stack for ENC28J60. All ...
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2answers
604 views

Battery powered sensor node power down circuit

I am using the BQ24079T to control power for a wireless, battery powered sensor node. The MCU will operate in one of two modes: periodic sample mode where it takes sensor readings and then sleeps, or ...
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3answers
2k views

Simplifying a relay network

I'm currently trying to design a relay network for a piece of laboratory equipment (PPMS). I would like to describe what the setup is, what I am doing now, what I hope to do, and how I hope to do it. ...
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4answers
4k views

Good solution for more interrupts on an arduino?

I'm building a circuit with an Arduino Mega and simple IC chips (e.g. 7432) but I have many lines to monitor for interrupt conditions and not enough pins on the Atmel so I'm looking for a way to ...
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1answer
2k views

Problem writing to MCP23017 I/O Expander registers (i2c)

I am creating a basic cable tester device and using I2C to interface with two MCP23017 I/O expander chips. In my code each MCP23017 slave has its own address and I can communicate with both of them ...
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2answers
1k views

GPIO Expander with isolation

Is there any GPIO expander with galvanic isolation? I browsed a lot and couldnt find any GPIO expander with isolation.Thanks in advacne
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3answers
1k views

Controlling more relays than the no. of free IO pins a uC has - Low-cost options

While I understand that moving up to a high pin-count uC might be the simplest option, I am looking for Low-cost options to do the same with low pin-count uC. Would like to control a maximum of 8 ...