Is it possible to connect the arduino UNO with the D1 mini wemos? Im trying to make a detector that will send out a message when it detects an event. So far I've been able to use the D1 mini to connect to a web server and send a message but I can't find a way to use the two together.
Yes, it is possible. Please provide a detailed description of what you are trying to accomplish with the Uno and D1 Mini connected. That will help us to be able to provide useful recommendations for how you might do this.
I am using the Arduino UNO to detect when a seizure occurs and the Wemos as a ESP8266 wifi module to send a message through a web server. What i need is to have the UNO tell the Wemos board when to send a message every time it detects a seizure
My idea was to just connect a pin from the UNO to the Wemos that way when a seizure occurs the UNO will send a signal but I wasn't sure whether its ok to connect the pins directly or if there is any precaution I should take like changing the voltage from 5V to 3.3V
percy1:
My idea was to just connect a pin from the UNO to the Wemos that way when a seizure occurs the UNO will send a signal
Sounds like a good idea.
percy1:
I wasn't sure whether its ok to connect the pins directly or if there is any precaution I should take like changing the voltage from 5V to 3.3V
Well, this is a controversial subject. If you look at the official documentation for the ESP8266, it doesn't say anything about it being 5 V tolerant. In fact there is even a statement to the contrary on the Espressif (the manufacturer of the ESP8266) website from one of their employees:
http://bbs.espressif.com/viewtopic.php?t=1145
IO and digital power supply of ESP8266EX ranges from 1.8V to 3.3V.
We donot recommend you to apply 5V to IO.
However, there is an obscure comment on the ESP8266 Facebook group from someone claiming to be the CEO of Espressif that says it is 5 V tolerant:
Teo Swee Ann: i can reply officially here: it is 5V tolerant at the IO. while the supply voltage is at 3.3V.
Although that comment was made 3 years ago, there is a follow-up to it made just two days ago by the CEO:
Chris Gimson: Teo Swee Ann Thank you for your very welcome official confirmation. This question crops up almost every day and there are a large number of uses who refuse to accept it because it is not in your latest spec sheets although it was in an earlier one. I would really appreciate it if you could explain (again) why you took it out of the spec sheet. Your response will be cut & pasted many many times in the future as this question pops up again so please be as clear as you can - the world is full of non-believers
Teo Swee Ann: Chris Gimson the reason is too many users took it to mean that the chip is 5 V tolerant. When we say 5 V tolerant, we are only referring to the IOs. So some users mistook this to make that they can power the chip entirely off the 5 V supply. The correct usage is to use 5 V open for these 5 V tolerant pins, and only via only drain configuration.
One thing is for sure, you won't do any harm by putting a resistive voltage divider on that line to convert the 5 V to 3.3 V.
Three typical diodes in series should drop 5v down to ~2.9v.
The correct usage is to use 5 V open for these 5 V tolerant pins, and only via only drain configuration.
This part makes the whole statement TERRIBLY ambiguous. If using an open drain configuration, the working voltage of the source is irrelevant, and recommending open drain suggests to me that the pins are NOT truly 5V tolerant.
In other "confirmations" of pins being 5V tolerant the connection to 5V was through a 10k pull-up resistor, like in an I2C configuration. That again doesn't confirm whether or not pins are 5V tolerant or not, as they presumably have clamping diodes keeping the thing safe. The clamping diodes would lower the bus voltage to 3.8V or so, still within spec of most if not all 5V devices to communicate properly.
Likewise, it's pretty much agreed upon that the regular Arduino pins are not 12V tolerant, yet connecting them to a 12V source through a 10k resistor is safe and even mentioned in Atmel application notes as a way to read a 12V signal. OTOH connecting a 12V power wire to a digital I/O (other than RESET) means instant death for an AVR MCU...
As it's easy enough to add a voltage divider I've never bothered to actually try connecting an I/O pin to a 5V power line. Even if that would be survived by that particular board is no guarantee the pins are in fact by design 5V tolerant. I seriously doubt they are, is it would add cost. Until it's explicitly written in the datasheet, I don't think it's so.
percy1:
I am using the Arduino UNO to detect when a seizure occurs...
Strange, because the Uno is not a sensor.
You must be using some sort of vibration sensor.
Can't you connect it directly to the WeMos.
Then you don't need the Uno.
Leo..