How to Program an ATtiny MCU by Using an ISP Header

If you have decided that the ATtiny MCU is the best choice for your project, then you need to choose a programming method.

In the previous article, the first ATtiny programming method we introduced was using the IC test clip as a way to connect the MCU to the Arduino IDE. Next, we will introduce the method of programming using the ISP header on the PCB and the AVR programmer connected to the computer.

Integrating the ISP header connector into the PCB design is the most common method of programming an AVR microcontroller on an assembled PCB. This programming method is extremely popular for small to medium production runs as it allows the microcontroller programming process to be completed while the PCB is being assembled.

What is an ISP plug?

The In-System Programming (ISP) header connector is typically a 6-pin 2x3 header connector, although an 8-pin 2x4 header connector may be used in some designs. The ISP header provides a standardized interface for transferring programming signals from an external programmer to the chip.

Common ISP plug.

You can find ISP headers on many DIY microcontroller boards, including many versions of the Arduino products.

ISP headers can also be found on popular DIY boards such as the Arduino Uno.

In-system programming is common in electronics manufacturing because it allows boards to be programmed during the production process without the need for a separate programming step.

For example, pre-programmed microcontrollers can be purchased from a variety of suppliers and only need to be soldered to a PCB to complete production. However, this adds complexity, cost and logistical overhead and is more common in high-volume production runs.

For smaller scale manufacturing, using an ISP header in the design allows the board to be programmed during a single production stage.

How to program ATtiny via ISP header

The test PCB used in this article has an ISP header to program any of the different ATtiny microcontrollers that can be put on the board.

The ISP header on the test PCB is six pins.

There are two common ways to interact with the ISP programming header:

● Use pogo pins

● By soldering a 2x3 pin male header to the board

Connection using Pogo Pins

The first is to make a temporary electrical connection via pogo pins. Pogo pins are spring-loaded contact pins that make a reliable but temporary electrical connection.

It is more common for makers to use a jig to make connections to the ISP header and simplify the programming process. However, you can create a simple system for programming prototype boards using pogo pins by simply plugging the pogo pins into an AVR programmer.

A simple Pogo Pin ISP programmer can be created by plugging the pogo pins into an AVR programming tool.

It is possible to connect an AVR programmer to the ISP header using pogo pins.

Use 6-pin male connector

The second method of connecting the ISP header is to solder a 2x3 pin male header to the board.

Header pins are available for easy connection to the ISP header.

This allows the AVR programming tool to simply plug into the board. Using a 2x3 pin header allows for a more secure connection, although this also increases the size and cost of the PCB.

The AVR programmer can be plugged directly into the ISP header pins.

There is also a minor difference in the way the Arduino IDE uploads sketches to a microcontroller via an AVR programmer versus a USB connection or IC test clip. Instead of pressing the "Upload" button, select Sketch > Upload Using Programmer.

To upload the code, select "Upload Using Programmer" from the "Sketch" menu.

Integrated ISP header is the best choice

Integrating the ISP programming header into the PCB design provides a standardized interface for programming the microcontroller after it is soldered to the PCB.

This method is useful for both prototyping and manufacturing. The ISP header is the most common method of programming a microcontroller in a product during the assembly process. The ISP header allows an AVR programmer to easily connect to the microcontroller.