Arduino Pro Mini 3.3v 8mhz - Optiboot?

I have a couple or three Arduino Pro Mini 3.3v MHz units that I wanted to use in a project. My code has a reliance on the Watchdog Timer which appears to be 'broken' in the common off the shelf boot loader delivered with my Arduino Pro Mini boards.

So i've been googling this and it appears that one solution is to replace the stock out of the box boot loader with another one called Optiboot. Is this my only or best option? Am I safe in assuming the problem with the standard out of the box boot loader will not be fixed as far as the Watchdog Timer goes?

Have read articles on this forum and general Google searching regarding replacing my boot loader and appears there are thousands of options/solutions 'out there' - which one is the simplest and most fool proof?

Guess I'm looking for a bit of an 'idiot' guide - including:
a) What to buy (if anything) and how to connect it
b) Step by step how to get Optiboot working on my Pro Mini 3.3v 8mhz units.

Thank you!

I've been in a similar boat in the past- I'm not too fussed about the WDT but the stock Pro Mini bootloader seems to take a long time to start up.
The easiest solution is to use Minicore. This gives you many more speed options to use. You can just select the processor and the speed, and then burn the booloader using an ISP programmer like USBASP. It is very simple.

dnienhis:
Am I safe in assuming the problem with the standard out of the box boot loader will not be fixed as far as the Watchdog Timer goes?

That's correct. Arduino doesn't manufacture or sell the Pro Mini (it's a SparkFun product) so they don't want to put any resources towards that board. The Nano, which they do sell, had the same problem but they recently solved that by switching to using the Optiboot bootloader on the official Nanos.

dnienhis:
Guess I'm looking for a bit of an 'idiot' guide

I agree with BJHenry's advice. I'll give you some more details:

dnienhis:
a) What to buy (if anything)

You will need an ISP programmer. I prefer the USBasp. Specifically, this one:

However, it is possible to make one of your Pro Minis into an "Arduino as ISP" programmer, following these instructions:

You will probably need the 10 uF capacitor between RST and GND pins on the Pro Mini that's being used as Arduino as ISP.

dnienhis:
how to connect it

For USBasp:

| ISP | | | Pro Mini |
| - | - | - |
| --- | | | -------- |
| MOSI | | | 11 |
| MISO | | | 12 |
| SCK | | | 13 |
| Reset | | | RST |
| +Vcc | | | VCC |
| Gnd | | | GND |

USBasp cable pinout:

Or if you're using an Arduino as ISP:

| ISP | | | Pro Mini |
| - | - | - |
| --- | | | -------- |
| 11 | | | 11 |
| 12 | | | 12 |
| 13 | | | 13 |
| 10 | | | RST |
| VCC | | | VCC |
| GND | | | GND |

dnienhis:
b) Step by step how to get Optiboot working on my Pro Mini 3.3v 8mhz units.

  • Install MiniCore, following these instructions: GitHub - MCUdude/MiniCore: Arduino hardware package for ATmega8, ATmega48, ATmega88, ATmega168, ATmega
  • Tools > Board > ATmega328
  • Tools > Clock > 8 MHz external
  • Tools > BOD > 1.8v
  • Tools > Variant > 328P / 328PA
  • Connect your ISP programmer to your target board
  • Connect your ISP programmer to your computer
  • Tools > Programmer > select the correct programmer
  • (only if you're using Arduino as ISP programmer) Tools > Port > select the COM port of the Arduino as ISP
  • Tools > Burn Bootloader

Thank you so much for all the help/input - my USBasp is on order!