I2C and SPI Max devices

#1

So I have a question, in before I pull the trigger on purchasing a bunch of sensors for a weather station project.

I am not experienced with SPI or I2C devices beyond plugging into the foundation plate or UI PCB. My project will be on a custom board for the pico to the pi-top as I am going to use @duwudi’s idea to get the pico to wake up the pi-top to run a custom script etc

Anyways is I understand SPI can have as many devices available depending on how many pins are available but what about I2C will I need some sort of multiplexer or something how do you use multiple devices?

While the sensors will be running on the pico I think the question is universal between the platforms

I can get most of the sensors as I2C bit not all are SPI but if I use Adafruit they certainly love STEMMA/qwik/qt or what ever it is

Will it help if I got a list of sensors that I will be looking at?

#2

SPI can have two devices as there are two chip select pins available, so you can flip between two different devices on the same bus.

For I2C you can have up to 255 devices on the same bus, the only requirement is that they must all have a different I2C address or they will clash. Some chips come with pins that can modify one or a few bits of the address just incase people want more than one of the same sensor on a bus

A list of sensors would be useful, send it over!

#3

Will get a list when not at work

#4

@duwudi here is what I am looking at, nothing set in stone, may buy all of them and more for testing

  • Adafruit BME280 I2C or SPI Temperature Humidity Pressure Sensor
  • Adafruit VEML7700 Lux Sensor
  • Adafruit TSL2591 High Dynamic Range Digital Light Sensor
  • Adafruit SGP30 Air Quality Sensor
  • Adafruit SI1145 Digital UV Index / IR / Visible Light Sensor

I am not sure how to handle rain fall, wind speed and wind direction at this moment

Will also need some sort of RTC for the pico, power management, battery and maybe even solar for recharging during the day and possibly an Micro SD card reader and i am going to get a couple rpi cameras

#5

Just got a delivery from a friend that had some spare oled screens I can certainly make use of these

image

1x 128x64, 2x 128x32. All are I2C and by MakerHawk. He is also digging out some old parts for me and sending a care package

1 Like
#6

@duwudi Guess who is going to have fun this weekendimage

image

1 Like
#7

@CAProjects: Lot of goodies😂. Keep us posted with your creations🙏
Also how did you get the groove and temp/humidity sensor to work on the pi-top? I have this IR receiver/emitter but its rated for 5V and I think the ports on the Universal PCB only output 3.3V, not sure if this would work but would be willing to try.
Screenshot_20210315-214613_Banggood

#8

I used the grove libraries for the sensors, should be able to use a library for it and use it, just check that the bower is the same on the device comparing with the pin outs, it’s the same as grove. If using the UI PCB just make sure it’s not analogue since the firmware is not flashed

The goodies in the images is basically what I listed in the 3rd post + SD card reader + Tiny 2040 + 3 spare RPi Pico

1 Like
#9

Do you have a link from where you pulled the libraries? Sorry for the noob question :joy:. Reason for asking is because I see various sources online and don’t know if one or the other works.
How are you finding the Pico so far? That Tiny2040 looks very very tempting.

#10

You would have to look for the library for the IR device

A comparison in size of the pico and Tiny 2040. They are the same processor just different form factor

image

#11

Wow, this is impressive, time to go shopping😂