. [This ALSO
applies to many other microcontroller IC's including the ATtiny85]
Let's assume you're already
familiar with
building circuits and programming 'sketches' around an Arduino
IDE development platform such as the Uno Rev3, Nano, Mega and other
more
compatible boards. In due time, you'll want to miniaturize or
self-contain your Arduino project in a smaller enclosure or wearable,
and you may also desire to make a permanent version of your project or
many copies of it and using actual Arduino UNO's or NANO's isn't
feasible. (Arduino Pro-Mini's are also $3+ ea.) In these cases
you'll
want to use just the heart of the Arduino, the actual AVR
microcontroller (MCU) IC such as the ATmega328p.
When working with Arduino (AVR) microcontrollers,
the
ability to upload sketches to a blank ATmega328p microcontroller IC
opens up a world of possibilities for custom projects. By
utilizing the ISP (In-System Programming) a.k.a. ICSP (In-Circuit
Serial Programming) protocol, you can program a bare ATmega328p chip
without the need for a preloaded bootloader. Below, I'll
describe
several options for uploading your sketches, including using an Arduino
development board like the Uno R3 or Nano, an off-the-shelf dedicated
programmer like the USBasp, or an FTDI interface.
Blank
vigin MCU chips weren't easy to find during the pandemic and subsequent
chip shortage, but are now plentiful again.
The prices aren't going to be as friendly as before due to
inflation, and Microchip, who now makes the ATmega328p and other older
AVR's is trying to sunset these 'obsolete' MCU families. But
ultimately, bare chips are way cheaper than whole Arduino boards
and there are still good stocks. Expect to pay around $3 USB a
piece for the 328p on DigiKey. If you
choose to build a custom PCB through a company like JLCPCB, PCBWay or
OSHPark you can get your boards with a factory fresh SMD ATmega328p-AU
pre-soldered on board for at least $7 a piece. If you go the proto-board route, a homebrew
option
with the ATmega328p-PU
DIP package will be the easiest.
You'll most likely be
starting off with a new chip which will be a blank slate as it will NOT come
with
a bootloader and you just can't wire it directly to a USB cable (don't
even...) The job of a bootloader is to provide a
Serial-to-USB interface link between the MCU and the PC and the initial
installation of a bootloader also sets some of the 'fuses' that sets
crucial working parameters of the MCU. You'll have to use a
programmer!
Please
familiarize yourself with the .PDF manual for this family of
Microchip/Atmel microcontrollers. [HERE]
[Bear
with me here as I build this page. My goal is to make this an
easy-to-understand and follow process.]
Should I burn a Bootloader
to my Atmega328p?
Understanding the Bootloader and Why You Might Not Need It for a Standalone ATmega328p
When setting up an ATmega328p microcontroller IC,
one of the first steps is often to burn a bootloader onto the chip.
But what exactly is a bootloader, and do you always need it?
A bootloader is a small program that resides in a
dedicated section of the microcontroller's memory. Its primary
job is to manage the uploading of sketches from the Arduino IDE to the
microcontroller via a USB interface, and it also sets certain
configuration fuses and internal registers that define critical
parameters like clock speed and memory allocation.
Why Burn the Bootloader?
For many standard Arduino boards, such as the Uno
or Nano, the bootloader is essential because it enables communication
between the microcontroller and your PC through a USB cable. This
makes it easy to upload new programs directly from the Arduino IDE.
However, when using an ATmega328p chip as a standalone device
without a USB interface, the bootloader's role becomes less crucial.
The primary reason to burn the bootloader initially is to
correctly configure the fuses and set up the microcontroller for the
desired clock speed, such as 16 MHz with an external crystal.
Once this is done, the bootloader itself isn’t necessary for
future sketches.
Advantages of Skipping the Bootloader in Standalone Applications
By programming your microcontroller directly through
ISP, you can skip the bootloader, gain additional memory, and enjoy
faster startup times — all without sacrificing functionality.
• Memory Savings: The bootloader
occupies a small portion of the microcontroller's memory, and by
omitting it, you free up this space for your program, allowing for
slightly larger sketches. • Faster
Startup: When a bootloader is present, it introduces a delay
during startup as it waits for potential incoming communication from
the IDE over USB.
Without the bootloader, your program starts running immediately
upon power-up.
Programming Without the Bootloader
If you plan to use the ATmega328p as a standalone
device without a USB interface, you’ll typically program it using an
ISP (In-System Programming) method, such as an Arduino configured as an
ISP (Arduino as ISP) or a dedicated USBasp programmer. Once the
bootloader is burned initially to set up the fuses, you can load
subsequent sketches directly through the ICSP (In-Circuit Serial
Programming) port, bypassing the bootloader entirely. This
approach is ideal for projects where you need to maximize memory usage
and reduce startup time. It also simplifies the microcontroller’s
operation, as it will no longer wait for USB communication before
executing your code.
While the bootloader is essential for USB-enabled Arduino
development, it’s not always necessary for standalone ATmega328p
applications. Keep these two things in mind:
• You are required to burn the bootloader
just once at first on any blank AVR microcontroller chip you plan to
use a programmer on so that crucial fuses can be set.
• Anytime you upload a sketch via an ISP
programmer - your bootloader will be deleted (unless you can specify
for it not to). If
you try to place your ATmega328p IC into the blank socket of an Arduino
Uno without a bootloader, it won't work! Just burn a bootloader
before doing so.
The method in this video relies on the
ATmega328p IC already being initially loaded with a bootloader and
simply acting in a remote
fashion as to when
it is programmed. This is not the direct ISP programming
method we'll be
discussing below but may be a more desirable method for ease of use.
It is possible to lock up (or "brick") your target
Arduino board or AVR microcontroller chip in the process of programming,
especially if the Reset line is
interrupted, an
incorrect setting is sent or any particular anomaly. Fixing
your
device
would then require a
High-Voltage
Programmer. Do not start off
following this on more important projects
but first try a few practice
runs. - The builder following this tutorial does so at their own risk.
See BELOW on building and using
an AVR High Voltage Parallel Programmer to un-brick your AVR micro...
.
Option 1: Uploading with Arduino Uno R3 (as
ISP):
Follow
these steps to use your Arduino as a Programmer:
BUT FIRST:
Make sure to read FIRST read Arduino's tutorial for
specific details that may vary from the below simplified step-by-step.
With this option, there's NO
need to purchase
an ISP Programming Shield or the like.
Step 1: Prepare the Arduino Uno R3:
a.
Connect the Arduino Uno R3 (Nano, etc.) to your computer via USB..
b.
In Arduino IDE, select "Arduino Uno" from the Board menu.
c.
Select the appropriate serial port in the Tools menu.
d. Build the Programmer
Circuit (As Shown Below) on your Arduino.
Step 2: Connections Wiring:
Connect the Arduino Uno R3 (Nano, etc.) to the
ATmega328p IC as follows: - You can ALSO
program another actual Arduino Uno (Nano, etc.)!
Arduino Uno 5V to
ATmega328p VCC [IC pin 7 /
Arduino 5v pin]
Arduino Uno GND to
ATmega328p GND
[IC pin 8 / Arduino Gnd pin]
Arduino Uno 10 (SS) to
ATmega328p RESET [IC pin 1
/ Arduino Reset pin]
Arduino Uno 11 (MOSI) to
ATmega328p MOSI MOSI [IC
pin 17 / Arduino pin 11]
Arduino Uno 12 (MISO) to
ATmega328p MISO [IC pin 18
/ Arduino pin 12]
Arduino Uno 13 (SCK) to
ATmega328p SCK [IC pin 19
/ Arduino pin 13]
Step 3: Burn the Bootloader (optional - but do so once before
uploading sketches):
a.
Select "Arduino as ISP" from the Tools menu.
b.
Select the appropriate board and processor from the Tools menu.
c. Open the "Arduino as ISP" Example sketch,
Upload
this to your Arduino.
d. Choose "Burn Bootloader" from the Tools menu.
Step 4: Upload Sketch to Blank ATmega328p IC (or
target Arduino device):
a.
Prepare your desired sketch in the Arduino IDE.
b.
Select "Arduino as ISP" from the Tools menu.
c.
Select the appropriate board and processor from the Tools menu.
d.
Click "Upload Using Programmer" to program the target device with the
sketch.
More descriptively:
>
1) Build
indicators as shown here:
_
2)
Make
connections between the programmer Arduino and the target device as
shown:
Programmer Pins:
Pin 13 - SCK
Pin
12 - MISO
Pin 11 - MOSI
Pin 10 - Reset (on Target
device)
.
Alternatively, for a
standalone setup for the ATmega328p make the protoboard connections as
shown:
This setup will allow for burning a bootloader as well as
any
subsequently loaded sketches.
The
same setup will apply for the ATmega328p-AU SMD package and many other
ISP capable AVR MCU's.
A few notes
on operation speed: A fresh blank and default ATmega328p IC out of the
box will have certain base-level fuses set from
the fab. Most crucially, is the operation speed where, instead of the
chip being set at 16 MHZ, it will be set to use
the internal oscillator which runs at ~8 MHz with a pre-scale speed
divider fuse set at /8 which means the chip will be set to
run at only 1 MHz and when a programmer tries to communicate with it, there may be a mismatch. Arduino IDE with the "Arduino as ISP"
setup, as pictured in the wiring diagram below, will automatically set these fuses which will
tell to the chip to run at 16 MHz with an external
crystal from then on out. If attempting to burn the bootloader fails
using the
Arduino as ISP
method, then first make sure that Port under the Tools
menu is set to the detected Com Port that the Arduino UNO (as
programmer) is connected to.
If using a USBasp programmer [Go HERE to learn more] you will NOT be able to burn the bootloader on a fresh chip
unless you bridge the jumper pins on the USBasp marked
"JP3" or "Slow SCK" as the USBasp will then know to work with the
Atmega328p
which will be running at 1 MHz. Once the bootloader is burned
through Arduino IDE, which will take at least 20 seconds,
Remove the
jumper after successful bootloader uploading. The chip will now
be set to run at 16 MHz with an external crystal and
burning bootloader
updates and uploading sketches will be possible at standard programming
speeds.
For
parts you will need: One 10k pullup resistor from V+ to pin
1 on the IC. For 16 Mhz
operation, either use an external 16 MHz
oscillator package, or use a
16 MHz crystal, and two ceramic capacitors valued at the specified
"load capacitance" of the crystal,
generally 20 or 22 picofarads. Also
add a 1 Meg-ohm resistor in parallel to the crystal which is for
stability but not crucial to operation.
Without those
components, the ATmega328p would need to run on its 8 MHz internal oscillator and appropriate measures have
to be made,
including using a specific bootloader along with running some setup
features from the AVRDUDE command line.
Certain 'fuse' bits would also need to be set. The 10
microfarad
electrolytic capacitor is for power supply smoothing.
Once programmed, all
wires from the programmer can be removed.
_
3)
In the Arduino IDE choose
"Arduino as
ISP" (In-System Programmer) under the Tools menu:
[Do NOT choose the "ArduinoISP" option as that is a specific
Arduino product]
_
4)
Open the "ArduinoISP" Example sketch in your IDE and
UPLOAD
this to your Arduino which will then make it the programmer:
[Remember to first remove the
capacitor from the Reset line if this procedure was done previously -
see below]
You
should see the "Heartbeat" LED fading in and out,
indicating that the programmer sketch is running.
NOTICE:
Make sure the Board: option under the Tools menu reflects the
device you're using as a programmer.
_
5)
AFTER uploading ArduinoISP sketch - add a 10uF
capacitor between Reset and GND on the programmer Arduino as
shown to disable rebooting.
NOTICE: Please
note the polarity of the capacitor. Remember to remove when
uploading
future sketches to this board in particular.
_
6)
To FIRST burn the bootloader or if you wish to make a fresh
AVR IC an "Arduino" -
Under
Tools - first choose the appropriate TARGET "Board:", then choose Burn
Bootloader:
_
7)
After uploading the bootloader, if you wish to directly
upload a sketch to a stand-alone AVR IC -
With the
target device connected via the ICSP port, open your desired sketch and
choose
"Upload
Using Programmer" from the Sketch menu.
[Do
NOT choose "Upload" as the
IDE will attempt to overwrite the programmer sketch on the host
Arduino.]
POWER
SUPPLY NOTICE:
Make sure that your target
board's power supply is isolated
from the programmer!
There could be a number of sensors or
devices in your project that may not work well with power provided
by your programmer
including 3.3v items. You may try just not connecting the
(+5v) line
between the two,
only sharing a common
ground connection - as long as the voltage of each device
is 5 volts.
It is advisable to isolate
the 5+ supply to the target AVR IC via a
disconnect
jumpers in your project, but even with that,
in a
complete circuit, the AVR IC may still unintentionally supply power to
connected devices through the I/O
and the current consumption
of your target's incorporated circuit may damage your programmer.
Consider programming the AVR IC by
itself on a
protoboard with its associated crystal and capacitors
or put both devices on the
same power supply.
PROGRAMMING: You
should see the
three indicator LEDs flashing in various sequences. The Error
LED
should not stay lit
and
the Programming
LED will now rapidly flash for a bit. The bootloader install
process should take just seconds
but
uploading a full 32k sketch may take more than half a minute.
If installed, you may
also
see the "built-in"
(pin 13) LED on your
target device flashing as well. Wait until the Programming
LED
has gone off and the
target AVR has rebooted
before removing the
connections and testing.
Consider building a
dedicated programming 'shield' for you Arduino that uses the [above]
wiring.
_
SAVING EEPROM
DATA:
If you wish to upload new sketches to your custom target
Arduino/AVR
without clearing or erasing any saved EEPROM Flash data on the AVR IC,
consider using the FTDI header if you have designed one in.
You will have
to have a bootloader resident,
but as FTDI
programmers are cheap and easy to find on Amazon, eBay and BangGood,
otherwise,
just upload the sketch through the ICSP port or write a sketch that
will transfer your EEPROM data to the Serial Monitor which can
be
pasted into a sketch that will send it back to a clean AVR IC.
Just remember
that
a sketch or bootloader upload via ICSP will also wipe all stored data!
_
.
Option 2: Using a Dedicated Programmer:
Dedicated programmers,
such as the USBasp or AVRISPmkII, provide a direct method of
programming ATmega328p ICs.
Follow these steps:
Step 1: Prepare the Programmer:
Connect the dedicated programmer to
your computer
via USB and install the necessary drivers and software required.
A dedicated AVR programmer
may require uploading your sketch through an IDE such as Microchip Studio.
Step 2: Connections Wiring:
Connect the programmer to
the ATmega328p IC is straight foward:
Step 3: Upload Bootloader to the Target Blank ATmega328p IC - If new from the the factory:
a. Open the
Arduino IDE and select
the appropriate board (Arduino Uno or Nano] and/or target
processor
from the Tools menu.
b. Choose the dedicated programmer (Arduino as ISP, USBasp, etc..) as the
programmer from the Tools menu.
c. If using a USBasp programmer (or similar), bridge jumper "JP3" for the "Slow SCK" mode as the new ATmega328p IC will be preset to run at 1MHz, otherwise the bootloader may fail to burn.
d. Click "Burn Bootloader" under the Tools menu to initialize and set crucial fuses for further programming.
Step 4: Upload Sketch to the Target Blank
ATmega328p IC:
a. Open the
Arduino IDE and select
the appropriate board (Arduino Uno or Nano] and target
processor
from the Tools menu.
b. Choose the dedicated programmer as the
programmer from the Tools menu.
c. Prepare your desired sketch in the Arduino
IDE.
d. Click "Upload
Using Programmer" under
the Sketch menu to program the ATmega328p IC with the sketch.
.
...
. Option
3: Utilizing an FTDI Interface:
An
FTDI interface can also be used to Upload Sketches to a prepared standalone ATmega328p IC and
are also a cheap alternative to a dedicated AVR programmer.
IMPORTANT:
The FTDI cannot set fuses and burn bootloaders as those require
an ISP interface - you must burn the initial bootloader with a
programmer (see Option 1 or 2:)
Follow these steps:
Step 1: Prepare the FTDI Interface:
Connect the dedicated programmer to
your computer via USB and install the necessary drivers
for the programmer if
required such as that for the CH340 IC (SEE HERE).
Step 2: Connections Wiring:
Connect
the FTDI interface to the ATmega328p IC as follows:
FTDI's 5V to ATmega328p VCC [IC pin 7 / Arduino 5v pin]
FTDI's GND to ATmega328p GND [IC pin 8 / Arduino Gnd pin]
FTDI's TX
to ATmega328p RX [IC pin 2 / Arduino 0 pin]
- Remember
that TX goes to RX
FTDI's RX
to ATmega328p TX [IC pin 3 / Arduino 1 pin]
and
vice-versa!
FTDI's DTR to ATmega328p
RESET [IC pin 1 / Arduino
Reset pin]
Step 3: Upload
Sketch to the Target Prepared Standalone ATmega328p IC:
a. Open the Arduino IDE and select the
appropriate board and processor from the Tools menu.
b. Choose the correct serial port of the FTDI
interface from the Tools menu.
c. Prepare
your desired sketch in the Arduino IDE.
d. Click
"Upload Using Programmer" under the Sketch menu to program the
ATmega328p IC with the sketch.
.
Uploading an Arduino IDE sketch to a
blank
ATmega328p microcontroller IC using the ISP (ICSP) protocol provides
flexibility and customization options for your projects. It should be
easy to use your trusty Arduino Uno R3 or Nano and a
solderless
prototype board, and using an FTDI adapter should only set you
back a few bucks.
More updates are planned for this section. Please feel free to correspond with me on relevant corrections or suggestions.
.
Nanos And Clones Waste Sketch
Space!
You
may be using the wrong bootloader!
Yes, if you run an Arduino
Nano (whether genuine or clone) or any clone "Arduino", you
may not be using the new,
improved and much smaller bootloader. You may also have a
much
slower upload speed. This should concern you because both the
Uno R3 and Nano use the SAME die chip!
Don't worry! The
YouTube channel, Design Build
Destroy will get you in the know and guide you
step-by-step to getting every
ounce from your Arduino:
_
__
_
A Parallel Programmer to Un-Brick
your AVR Microcontroller:
So you've somehow killed your ATmega328p or other
AVR
micro in the process of programming via ISP! Learn how to
recover the full potential of your AVR by manipulating the fuse bits
and salvaging 'bricked' chips. Sine Lab gives you a
step-by-step demonstration to guide you through the setup of your own
parallel programming system. Learn how to interrogate your
Arduino's brain by hand on a protoboard and build a permanent rescue
board. Also works on many other 28-pin AVR chip varieties.
Arduino Projects By Mike, K4ICY 
