Fully automatic coffee machine design ACM32F070 MCU controls the coffee machine system

Nowadays, as people's pace of life continues to accelerate and their living standards continue to improve, coffee, as one of the most popular drinks in the world, has entered people's daily lives and is gradually loved by more and more people. As a result, "coffee machines" have become more and more popular. To brew a perfect cup of coffee, you need to use a special coffee machine. The coffee machine uses about 10 atmospheric pressures to force hot water at about 90°C to pass through about 10 grams of squeezed coffee powder, extracting aromatic substances such as coffee fat in the coffee powder, and then fully dissolving it with hot water before flowing into the cup. The whole process needs to be completed within 18-28 seconds to effectively avoid the bad taste caused by over-extraction. Obviously, the coffee machine plays a decisive role in making a cup of high-quality coffee.

This article will introduce the design of a coffee machine based on Shanghai Hangxin ACM32F070.

1

Coffee Machine Overview

There are many coffee machines on the market now, which can be divided into two types according to their operation methods: semi-automatic and fully automatic.

The main features of semi-automatic coffee machines are: manual operation of grinding, pressing, filling, brewing, and cleaning residues, etc. The machine has a simple structure, is easy to maintain, and is convenient to use. Its disadvantages are: high requirements for operators, operators must undergo rigorous training to use this machine to make high-quality coffee, and the work efficiency is low.

The main features of the fully automatic coffee machine are: it realizes automatic control of the entire process of brewing coffee, including grinding, pressing, filling, brewing, and removing residues. It is more convenient and quick to use, with consistent quality and high efficiency. It does not require high operator requirements and does not require training. Its disadvantages are: it has a relatively complex structure, requires good maintenance, and has high maintenance costs. However, due to its outstanding advantages, it is increasingly loved by many customers.

The coffee machine design introduced this time is a fully automatic coffee machine that can brew coffee according to the most scientific data and procedures, and is equipped with a complete protection system. It is simple and convenient to use, and you can get coffee with just one click. Users can set the water temperature and coffee grinding fineness, and can automatically grind coffee beans; users can also choose to make a single cup or two cups of coffee at the same time according to their needs, and three options are also provided: large cup, medium cup, and small cup. In addition to making coffee, this coffee machine can also make hot water and steam. The hot water can be used to make tea or other drinks; the steam can be used to heat milk or other drinks, and the high-pressure steam can also emulsify the milk to create fragrant milk foam. It can provide users with diverse, easy and fast services.

2

Chip Features

ACM32F0X0 series is a general-purpose MCU that supports multiple low-power modes. It integrates 16-channel Touch buttons, 12-bit 1.6 Msps high-precision ADC, analog comparator COMP, operational amplifier OPAMP, segment LCD controller, built-in high-performance timer TIMER, multiple UART, LPUART, SPI, I2C and other rich communication peripherals, built-in AES, TRNG, CRC32 and other information security modules, supports multiple low-power modes, and has the characteristics of high integration, high anti-interference, high reliability, etc. This product uses a high-performance core with a maximum operating frequency of 64MHz.

Figure 2. ACM32F0X0 resource map

Touch button TKEY

The ACM32F0X0 chip has a self-capacitive touch control sensor integrated inside. The self-capacitive touch control sensor detects whether a finger touches the touch surface by detecting changes in capacitance. The sensitivity of the touch is adjusted by adjusting the amount of capacitance change detected.

• Highly integrated, supporting up to 16 touch keys TKEY;

• Self-capacitance detection range 5~50pf, sensitivity 0.1pf;

• Support channel compensation;

• Supports touch panel thickness up to 10mm;

• Support low power sleep mode, the lowest power consumption in Stop mode is 17uA;

• Support setting the sensitivity and scanning speed of working mode and sleep mode separately;

• Supports active shielding Cshield channel for waterproof control and increased detection sensitivity; can reduce parasitic capacitance, reduce noise source interference from parasitic capacitance, and increase TKEY stability when other conductors are close to touch electrodes;

• Supports filtering and anti-shake mechanism, which can reduce false touches and avoid interference caused by static electricity;

• Support adaptive and self-calibration mechanisms to reduce interference from environmental variables;

• We simulated the customer usage environment and conducted repeated tests for a long time to ensure the reliability of the product. The test methods are as follows:

① Humid environment test: Spray water vapor onto the touch panel to make it full of dew. There will be no false touches or slow responses.

② Splash and flood test: Spray water on the touch panel quickly until a puddle is formed on the panel, and several different touch sensing electrodes are flooded into a puddle. At this time, there is no false touch, slow response, or triggering of the B key in the same puddle when pressing the A key, that is, the phenomenon of pressing the key in the wrong direction;

③ High and low temperature test: -40℃~85℃ high and low temperature test, there is no phenomenon of false touch, slow response and freezing;

④ Electromagnetic interference test: Use a wireless walkie-talkie as the RF interference source, make calls and intercoms about 20cm away from the touch panel, and there will be no false touches, slow responses, or freezes;

⑤ Power supply interference test: A strong high-voltage pulse group of 600~800V is formed on the power grid, and there is no false touch phenomenon at this time;

⑥ Long-term continuous working test: The prototype has been tested for 6 months of uninterrupted long-term working without power failure. The buttons work normally without any unresponsiveness or freezing.

Liquid crystal controller LCD

The ACM32F0X0 chip integrates a digital controller/driver for monochrome passive liquid crystal displays (LCDs) with up to 8 common terminals (COM) and 40 segment terminals (SEG) to drive 160 (4*40) or 288 (3*36) LCD elements.

• Highly flexible frame rate control;

• Supports static, 1/2, 1/3, 1/4, 1/6 and 1/8 duty cycles, and supports 1/2, 1/3, 1/4 bias;

• LCD data RAM with up to 16 registers;

• LCD contrast can be configured through software, LCD flicker function is supported, and multiple flicker frequencies can be configured;

• Supports Class A and Class B waveforms, and 2 drive waveform generation methods:

① Internal resistance voltage division, external resistance voltage division;

② Optional filter capacitor;

③ The power consumption of the internal resistor voltage divider can be configured through software to match the capacitor charge required by the LCD panel;

• Support low power mode: LCD controller can display in Active, Sleep and Stop modes.

Operational Amplifier OPAMP

• Low operating voltage, typical operating voltage 3.3V; low current consumption, typical value 115uA;

• Offset voltage can be trimmed.

Analog Comparator COMP

Used to compare the sizes of two input analog voltages and output high and low levels based on the comparison results.

• The comparator output can be used as the brake input or capture input of the timer;

• Provide software configurable filtering time to enhance the chip's anti-interference ability;

• The comparator output can be cut off by a timer.

12-bit 1.6Msps high-precision ADC

Supports single-ended signal conversion and differential signal conversion, up to 21 channels, supports up to 16 settable channels of regular conversion, and 1 settable channel of injection conversion. Each A/D conversion can be performed in single, continuous or discontinuous mode.

High performance timer TIMER

The ACM32F0X0 chip has a built-in advanced timer, which consists of a 16-bit auto-load counter, driven by a 16-bit programmable (can be modified in real time) prescaler. The advanced timer and the general timer are completely independent, they do not share any resources, but they can operate synchronously.

• Up to 4 independent channels (input capture, output compare, PWM generation, single pulse mode output); can measure the pulse width of input signals (input capture), can generate output waveforms (output compare, PWM, embedded dead time complementary PWM, etc.)

• Supports incremental (quadrature) encoder and Hall sensor circuits for positioning;

• Support three-phase PWM, dead zone protection, and brake control;

• Support sensory, sensorless and FOC control algorithms;

3

Design

The coffee machine solution described in this article is designed based on the Shanghai Hangxin ACM32F070 series MCU. The overall solution block diagram is as follows:

Figure 3. Block diagram of coffee machine design based on ACM32F070

The download link of software resources (touch button part) is as follows:

https://gitee.com/acm32-mcu/ACM32F0X0-Coffee-TKey-Demo

https://github.com/ACM32-MCU/ACM32F0X0-Coffee-TKey-Demo

Digital intelligent control

The human-computer interaction function in the design scheme discussed in this article is implemented by LCD, LED, and touch buttons. There is a total of 1 segment LCD screen, 9 buttons and 10 LEDs. The buttons need to realize the device's power on and off, mode selection (steam mode/coffee mode), large, medium and small cup selection, one cup or two cup selection, coffee bean grinding coarseness setting, coffee strength setting, temperature setting, and child lock function. The device will determine the current operation to be performed based on the button indication. 9 of the 10 LEDs are used for button indication, indicating the operation currently being performed; the other 1 LED is used for alarm indication, mainly when the device is self-checking, if the residue box, residual water tank, motor, core components, etc. are not reset, the indicator light flashes. The LCD screen is used to display the coffee bean grinding coarseness, coffee strength, temperature, large, medium and small cup indication, and one cup or two cup indication.