Daisy Chain LCDs - Raspberry PI

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jtemple967
 
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Daisy Chain LCDs - Raspberry PI

Post by jtemple967 »

So I'm in the beginning stages of working on a project where I want to have a single RPi (Pico) control 4 separate LCDs. I've seen a few posts on daisy chaining LCDs but not sure if that would apply to simple LCDs. Could I daisy chain 4 to one RPi? If so, is there any guidance on how I would connect them and then what would I do differently in MicroPython to send different text to each LCD?

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adafruit_support_mike
 
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Re: Daisy Chain LCDs - Raspberry PI

Post by adafruit_support_mike »

It depends on the communication protocol of the display you use, and the way you choose to define 'daisy-chaining'.

If you plan to use HD44780-like character LCDs:

https://www.adafruit.com/?q=lcd+bc&sort=BestMatch

you can connect each one to an I2C backpack and control all of them from a single pair of SDA/SCL lines:

https://www.adafruit.com/product/292

Electrically, all the backpacks will be connected to the I2C bus in parallel, but you can run the physical wiring from one board to the next, which people often call 'daisy-chaining'.

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jtemple967
 
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Re: Daisy Chain LCDs - Raspberry PI

Post by jtemple967 »

Thank you! I will read up on these while I'm waiting for more RPi Pico Ws to arrive.

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jtemple967
 
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Re: Daisy Chain LCDs - Raspberry PI

Post by jtemple967 »

Mike could you recommend a feather board that would have comparable features to the pico w that I could use for this project? It would need to be able to be seen as a midi device through USB, have WiFi, have at least 8 io ports and be able to support an external display like the https://www.adafruit.com/product/4741. Also being able to daisy chain basic lcds would be a plus.

I'm thinking of using a feather since it looks like we'll be waiting for the pico w for a while

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adafruit_support_mike
 
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Re: Daisy Chain LCDs - Raspberry PI

Post by adafruit_support_mike »

All of the Feather M0 or Feather M4 boards handle USB internally, so they can connect to a computer as a USB MIDI device.

Doing Wifi with a microcontroller tends to involve a lot of bookkeeping to keep the Wifi part running while you handle the other code, so we've created the AirLift ESP32 Wifi coprocessors:

https://www.adafruit.com/product/4264

The ESP32 is a System-on-Chip (SoC) Wifi/Bluetooth/BLE device, and we've given it an interface that makes network communication much easier on the client microcontroller side. Instead of handling tons of time-critical interrupts, your code can just say, "get me this webpage".

The OLED display (pid 4741) uses I2C to communicate, so it will talk to pretty much anything. I2C is one of the most common protocols for connecting microcontrollers to external devices, so almost all microcontrollers have hardware for it. I don't think we carry anything programmable that doesn't do I2C.

One of the most popular features of I2C is the ability to control many different devices through the same pair of SDA/SCL lines, so using the OLED and a bunch of character LCDs would be no more difficult than plugging in the connections.

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