1. How Do the Apollo Computer and a $4 Board Compare in Speed and Memory?
The Apollo Guidance Computer (AGC) had a clock speed of 2.048 MHz and 2,048 words of rewritable memory (RAM). Since 1 word equals 16 bits, this is about 4 kilobytes. Its read-only memory was 36,864 words, or about 72 kilobytes. The computer weighed about 32 kg (about 70 lbs) [1][2]. In contrast, the RP2040 chip on the Raspberry Pi Pico has a maximum clock speed of 133 MHz and 264 kilobytes of SRAM [3]. The board is listed on the official page as starting at $4 [4].
If you divide the numbers, the RAM is 66 times larger (264 ÷ 4) and the clock speed is about 65 times higher (133 ÷ 2.048). However, these ratios only compare specification numbers. They do not mean the new chip is "66 times faster." This is because the types of instructions and the number of bits handled at one time differ between the two. Also, the RP2040's clock speed is a maximum value. The main component on this board is a microcontroller. How does it differ from a computer chip?
2. What Is a Microcontroller, and Which Parts Does One Chip Contain?
A microcontroller (MCU) combines basic parts—CPU, ROM (read-only memory), and RAM (rewritable memory)—into one integrated circuit (IC). It is used for lighter tasks, such as controlling toys or microwaves [5]. Washing machines and telephones also use them [6]. Imagine a small shop where one person does everything. The staff member is the CPU, the posted notices are ROM, and the notepad is RAM. The doorways for signals to enter and leave are the input/output pins. This is just a metaphor; the chip runs on electricity.
The RP2040 has 30 general-purpose input/output pins (GPIO). Four of these can also be used for analog inputs [3]. A basic use of a microcontroller is connecting buzzers or lights to these pins and making them sound or glow via a program. When and why were these chips created?
3. How Did Calculator Chips Lead to the First General-Purpose Microcontrollers?
Microcontrollers grew out of work on calculator chips. In 1971, Gary Boone and Michael Cochran at Texas Instruments (TI) in the United States designed a single chip for calculators (TMS1802). This became the foundation for the "TMS1000" family of 4-bit microcontrollers, which could be used for things other than calculators. They were announced in 1974 [5]. Some sources say the "first microcontroller" was in 1971, while others say 1974. This difference comes from separating the design year from the year it was announced as a general product.
The TMS1000 cost $2 per unit when bought in large quantities [5]. This low price led to the spread of uses seen in the next section. Where can we find these microcontrollers today?
4. How Were Microcontrollers Used in Toys and Home Appliances?
The TMS1000 was used in security buzzers, garage door openers, games, and toys like "Speak and Spell." It brought digital electronic circuits closer to everyday people [5]. Today, microcontrollers still run inside washing machines and microwaves [6].
They are also in cars. A 2012 report by the Information-technology Promotion Agency (IPA) stated that a single car might contain over 100 electronic control units (ECUs) and about 10 million lines of software [7]. Note that one ECU is not always one microcontroller. These numbers are from a 2012 report and may not apply exactly to current car models. What things at home use these chips?
5. Why Was the Arduino Board Created for Students in 2005?
In 2005, Arduino was created at the Interaction Design Institute Ivrea (IDII) in Italy as a cheap electronics board for students [8]. At that time, existing microcontroller boards like the BASIC Stamp cost about $100 for the board and basic parts. This was expensive for students. The goal was set at about $30, roughly the price of one meal at a pizza restaurant [8]. This $30 was a design target; actual sale prices have changed since then.
Arduino is open-source hardware and software for students, hobbyists, artists, programmers, and experts. Its mission is to make electronics and digital technology accessible to everyone [9]. Can we meet these familiar microcontrollers at home?
6. How Can You Find Microcontroller Devices at Home That Respond to a Button?
Look for things at home that respond when you press a button. Examples include microwaves, washing machines, and toys. Make a list of items that might have a small computer inside. However, do not open the appliances or toys. Disassembling them can cause injury or damage. Only observe the movement from the outside when you press a button.
You cannot see the type of chip inside from the outside. Talk with your family about "how this works." If you want to know more, looking for electronics books at the library is a good method.