How to tell if the arduino pro mini is 5V (16mhz) or 3.3V (8MHZ)

if it is not checked on the back side, the simplest and fastest way to do this is to look at the resonator, (Clock) – usually a Crystal oscillator, but I don’t see why it can’t be a ceramic resonator, if it has something with an 8 in it, then it is probably an 8MHZ resonator, otherwise it is probably 16, where 8 comes with the 3.3V and 16 with the 5V (Scroll down to see an example)

Another way is to connect the RAW to, let’s say 12V or even 5V, and measure the voltage at the VCC pin, that would also tell you, but surely, this involves more than just looking at the board, you need to connect wires and a power supply !

mine reads 80 u (something that looks like the letter U) so it is 3v3, here is a photo

Programming the 3.3V arduino pro mini with a CP2102 breakout

The CP2102 breakout board shown in the photo below has a selector between 3.3V and 5V.

In my case, i simply connected it the way you see it here to a USB port with 3.3V, and what do you know, it works, I have a flashing red light on the Arduino, a constant green light, and it looks like it is read to take code, the CP2102 board has a constant red light.

if you want to check that it is actually working fine, simply upload the sketch blink no delay, and then alter it a bit so that it does a double blink then wait 2 seconds, now your code is working, there you have it.

From the device manager, I can see that there is a device that looks like my adapter, namely this one

Silicon Labs CP210x USB to UART Bridge (Com3)

That thing above tells me that it has been designated the communication port number 3, which i will need in the Arduino IDE

So now i have installed and am running the Arduino IDE, selected a 3.3V Arduino board from the list and selected Com3, now i should be ready to upload a sketch, let us make a sketch that double flashes an LED every 2 seconds. here is some code to do that

The cheapest 3.3V power supply using the LD33CV (LD1117V33)

To create a tiny power supply to turn a 5V power source into 3.3V for powering the ESP8266 or ESP32, or maybe an Arduino pro mini (3.3V version), all you need to do is to couple the LD33CV-LD1117V33 with a pair of capacitors, in my case I am using the 25V/100 uf capacitor

All you need to do is the following

connect one capacitor to the pins 1 (Vin) and 3 (GND), and the other to the pins 2(Vout) and 3 (GND), and you are done.

At this stage, the ones between 1 and 3 will receive the input 5V power, While the ones closer to each other (2 and 3) will have the 3v3 output voltage that you can connect directly to your Arduino or ESP micro controller

The LD1117V33 you see above (LD33CV) comes in a TO-220 package, and uses an NPN pass transistor for efficiency to provide up to 800ma of power (Cooling may be needed to achieve maximum)

GPS / u-blox and Adafruit-Mediatek

The things i add here are primarily for my reference, but they could save you a lot of time, so here i am only covering the practical side, wikipedia can help you with the theory. things here are sort of in random order, so feel free to use your browser’s search facility.

I have the following positioning systems/chips/boards, so most of the stuff you will find here will relate to them

* V.KEL VK2828U7G5LF TTL Ublox GPS module with antenna: supports GPS, GALILEO, SBAS (WAAS, EGNOS, MSAS, GAGAN)
* K-172 USB GPS USB Receiver Dongle Adapter Smart Antenna Module For Gmouse Glonass, also running u-blox, Support NMEA 0183 and ublox binary protocol.
* The ADAFRUIT ultimate breakout board with the MTK3339 chip (Not U-BLOX), but rather mediatek

A-GPS and AssistNow:

The long story short: A-GPS seems to be when the satellite data is available in advance, whether you allow your system to download it from the internet as it goes, or you download it in advance and make it available to the system, it boils down to telling your system where the satellites are and their relevant data rather than wait for your device to download that data from the satellites at very low speeds (Sat data is downloaded at a maximum of 50 bits per second, so getting the data over the internet or from the SD card in your raspberry pi or arduino etc is much much faster).

AssistNow is how the U-Blox A-GPS works

1- A-GPS only work out of the box with u-center, the software by u-blox, on your raspberry PI or arduino, it will not work out of the box , to make it work you need to look online for software that does that (It’s on github)

the online edition is when the data is downloaded from the internet in real time (when it is needed), the AssistNow  offline is when you download “AlmanacPlus® Differential Almanac Correction Data” from the internet and store it with your device (On whatever is driving the device, be it a PC, laptop, raspberry pi, arduino etc…)

2- The adafruit GPS raspberry pi board does A-GPS in a different way, which works out of the box, they add a battery to the board, and once data is downloaded once, it stays on the board for as long as there is a battery 😉