I am making my own version of a Mega 2560 board and I have some extra board space. Does anyone have some ideas of what I should put there? I was thinking a bluetooth chip might be cool. Let me know if you have any suggestions, and if you could, please put some reading material about your idea so I can learn how to put it in my layout.
Design specifications:
-Board is designed to run at 5V
-Main pins must remain in normal locations so as not to interfere with existing shields and such
-There is a 5V and 3.3V regulator, the 5V can supply 1ADC, and the 3.3 can supply 1.5ADC
I would suggest an ESP-01 or better an ESP-12 module
optionally connected to one of the free Serials with level shifted TX, or a level shifted I2C connection for E12.
A NRF24L01+ module
optionally connected to an interrupt pin and with a capacitor near the module.
There are some very small ones too.
Both modules draw some current on the 3.3V line which the board should be able to deliver.
ESP8266 module - you can fit an ESP-01M into a very small amount of board space.
You could probably fit pins for NRF24 and a bluetooth module in too if you were careful with the layout? Then again, if the board's going to run at 5v, you need to provide for level shifting to 3.3v, so that might make it harder to fit.
Do you have a decoupling cap on every pair of Vcc and Gnd pins around that '2560?
I also don't see the crystal or resonator for the '2560? You need one if you want serial to function reliably - the internal oscillator isn't accurate enough to guarantee that it will work (it may, at some voltages and temperatures, with some individual chips)
Also, add some more power and ground pins, not everyone uses breadboard, and for reasons unclear to me, there don't seem to be readily available Y-shaped dupont jumpers.
DrAzzy:
ESP8266 module - you can fit an ESP-01M into a very small amount of board space.
You could probably fit pins for NRF24 and a bluetooth module in too if you were careful with the layout? Then again, if the board's going to run at 5v, you need to provide for level shifting to 3.3v, so that might make it harder to fit.
Do you have a decoupling cap on every pair of Vcc and Gnd pins around that '2560?
I also don't see the crystal or resonator for the '2560? You need one if you want serial to function reliably - the internal oscillator isn't accurate enough to guarantee that it will work (it may, at some voltages and temperatures, with some individual chips)
Also, add some more power and ground pins, not everyone uses breadboard, and for reasons unclear to me, there don't seem to be readily available Y-shaped dupont jumpers.
The necessity of 3.3V signals was my main concern with bluetooth and many IoT chips. I can add logic level converters but that can take a lot of space.
On the actual schematics from the Arduino Mega page, there are only three decoupling caps for the 2560. I didn't add any extra seeing as how it works with the three, but I can always add more.
For the crystal, there is a small set of three pads close together next to the three big tank capacitors. These are the pads for the resonator (which has internal caps), and the 1M resistor.
I can add a small rail for more 5V and ground connections if necessary.
Ideally there would be ALL pins, like this plug-on-Mega board, but that's not possible...
Thanks for the input. More connectors for the digital pins would be great. One of my requirements is to keep the standard pin layout so shields and such are not hindered. Adding another set of connectors for the main (2-13) digital pins would be a tad difficult, but I will keep it in mind! Please feel free to suggest other devices/ideas
Does anyone know of some bluetooth devices to interface with a smartphone or tablet? I'd even be willing to put some headers to fit an Adafruit feather and communicate via I2C or something (with shifted voltage levels of course)
bos1714:
Does anyone know of some bluetooth devices to interface with a smartphone or tablet? I'd even be willing to put some headers to fit an Adafruit feather and communicate via I2C or something (with shifted voltage levels of course)
Sparkfun and Adafruit know lots of bluetooth modules. Why not look at their guides?
I've been playing with the Simblee recently. That makes it easy to do the phone app because there's zero programming on the phone side.
MorganS:
Sparkfun and Adafruit know lots of bluetooth modules. Why not look at their guides?
I've been playing with the Simblee recently. That makes it easy to do the phone app because there's zero programming on the phone side.
I've been looking through Adafruit, but since I am not familiar with bluetooth or IoT stuff I wasn't entirely sure what is what. I will give sparkfun a try as well.
Whandall:
Yes, it's a great chip, dual processor (160 MHz) lots of RAM and Flash.
What about this board from Adafruit. It seems to have the same chip you mentioned. I can use the space in the original picture for some logic level converting and extend the board another inch or so and put headers for the board to plug into.
There are many ESP32 boards, the linked to and some other support LiPos with charging logic.
How would you integrate that functionality?
For the Mega you would need a step up converter or run into problems with backpowering
it from the ESP32 connections.
I was going to power the feather from the 3.3v supply from the board. The regulator I have in mind can put out 1.5ADC if needed so that shouldn’t be a problem. I simply won’t use a LiPo for the feather. As I mentioned I can use level converters for the communication channels as well as gpio pins
