![]() ![]() If you just want to drive LEDs you can usually multiplex them. This had 9 chips driving the columns (9 x 8 = 72 LEDs) and one chip driving the rows, in a multiplexed configuration. I found inside a commercial LED sign that the 72 LEDs were driven by 74HC595 chips. In this example I am controlling 32 LEDs with only 3 I/O pins (MOSI/MISO/SCK) plus power and ground. Using SPI you can send fast serial data to a shift register, such as the 74HC595. These are bi-directional, so can be used as an input or output expander. You can use analog multiplexers like the 74HC4051 (8 ports) or the 74HC4067 (16 ports) to connect one pin to one of the 8/16 ports (but only one at a given time), like this: Some third-party manufacturers have made boards with 4 x MCP23017 on them, this gives you 64 inputs/outputs: Now we connect to the Arduino using only 2 wires (SDA/SCL) plus power and ground: As inputs they can raise interrupts if desired.Įxample of connecting 13 of those 16 to the LCD: The MCP23017 has 16 ports, which can be configured as inputs or outputs. I used one of those chips to connect to an LCD board. You can use the I 2C protocol (Wire library) to connect to other devices such as port-expanders. The latch pin is used to keep the 595 outputs steady while you are shifting out data into it, like so: digitalWrite(latchPin, LOW) Arduino Platform - Working with Shift Registers.The figure above was taken from this webpage: The resulting circuit (using one 595) would look like this: You also must connect together the clock and latch pins of all of the 595 ICs. To get more outputs, you can daisy-chain a series of 595 together, by connecting its serial-out pin, to the data pin of the next one. With one 595, you gain 5 pins (8 on the IC, but you spend 3 to talk to it). With that command, you set each of the 8 outputs on the 595 IC with the 8 bits in the data variable. ![]() In a program, you pass on the data one bit at a time to the shift register using the shiftOut() command, like so: shiftOut(dataPin, clockPin, data) Have concerns that weren’t answered here? Please email so we can help.A common way to expand the set of available output pins on the Arduino is to use shift registers like the 74HC595 IC ( link to datasheet). We hope you enjoy your cool new stuff and we’d love to see your photos of them on social media! Thank you so much for your kind and generous support of Maximum Fun! Thank you again for a fantastic MaxFunDrive in a not-so-fantastic year! And if you purchased pins, thank you so much for partnering with us to get low income folks access to computers and affordable internet through EveryoneOn! Once everything has shipped, we’ll calculate the proceeds of the pin sale and make our donation to EveryoneOn (we’ll be sure to let you know how much the MaxFun community raised when we officially make that donation). It will definitely take extra time for packages to make it to our overseas friends – most likely several more weeks – depending on how long things take to go through customs. If you did not change your address in our system, but you did set up mail forwarding, your package should find you at your new address if it is going through USPS (our tracking email will let you know what carrier your package is being sent through) it may just take some extra time. If you have moved (and did not update your address in response to the email we sent out), your package will most likely be returned to sender, and we will contact you about shipping it back out. If your address has changed and you did NOT update it when we sent our emails out:Īt this point it is too late to change your shipping address. So, if you get one package before the other, or if you see your friends posting photos of their awesome swag - don’t fret, your stuff is headed your way soon! It just takes time to get through every package. You’ll receive a separate email with tracking information for your MaxFunDrive gift package in the coming weeks. This is old news, but if you purchased pins during the pin sale, those will be shipping separately from any MaxFunDrive gifts you are expecting. Please be patient while our fulfillment centers work their magic, and please be sure to check your spam folder for that email! If you are getting MaxFunDrive gifts, those ship separately from purchased pins. When your package has shipped, you will get an email that includes your tracking number. Here’s a bit of general info: We will have tracking numbers for you! It’s happening! Our fulfillment centers are starting to get your gifts and pin orders ready to go out the door. ![]()
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