Touch Key LCD Display Card Reference Design WAS-19C1EN V1.00 1 / 11 September 25, 2020 Touch Key LCD Display Card Reference Design D/N: WAS-19C1EN Introduction Smart cards integrated with a password display function are called display cards. The display card is turned on by entering a PIN code. This PIN code is then used along with the entered transaction information to calculate an SHA dynamic password (TOTP) which is then displayed on an LCD screen. This improves the security of e-banking login and reduces the possibility of transaction loss due to phishing websites. The display card has an integrated paper battery with a capacity of 15mAH which can provide a guaranteed battery life of 3~5 years. Figure 1 Application Areas e-Banking, touch key LCD display cards, ultra-low power touch key + LCD products. Solution Features 1. Ultra-low standby current: the product 1-key wake-up standby current is 130nA@3V. The BS67F2563 includes a low frequency 32768Hz crystal oscillator circuit. Its extremely low oscillation current allows a 1-key standby current of 130nA@3V(Typ.) for the product. It can be used for accurate time counting combined with an internal Time Base counter. 2. High level of functional integration: only a few external components are required. The BS67F2563 includes up to 20 internal capacitive touch keys with the touch sensitivity adjustable by firmware to fit into different materials or media. The integrated C-type LCD driver reduces power consumption when the LCD display is being used.
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Touch Key LCD Display Card Reference Design...LCD displays “-----” LCD shifts to the right and displays the current digit Y N Y Y Y Y N N N Touch library initialization USER_PROGARM
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Touch Key LCD Display Card Reference Design
WAS-19C1EN V1.00 1 / 11 September 25, 2020
Touch Key LCD Display Card Reference Design
D/N: WAS-19C1EN
Introduction
Smart cards integrated with a password display function are called display cards. The display card
is turned on by entering a PIN code. This PIN code is then used along with the entered transaction
information to calculate an SHA dynamic password (TOTP) which is then displayed on an LCD
screen. This improves the security of e-banking login and reduces the possibility of transaction loss
due to phishing websites. The display card has an integrated paper battery with a capacity of
15mAH which can provide a guaranteed battery life of 3~5 years.
The library provides touch key related parameter settings whose details are as follows:
Parameter Name Function Value Range Recommended Value
SystemClock System frequency selection
0=4MHz 1=8MHz 2=12MHz
0
DebounceTimes Debounce times 0~15 2
AutoCalibrationPeriod Auto calibration period setting 0~15 4~8
HighSensitive High sensitivity setting 0=Off; 1=On 0 MaximumKeyHoldTime Maximum key hold time 0~15 1 (4 seconds) FastResponse Fast response setting 0=Off; 1=On 0
AutoFrequencyHopping Auto frequency hopping setting 0=Off; 1=On 1
OneKeyActive 1 key or all keys active 0=All keys active 1=One key active
1
PowerSave Low power setting 0=Off; 1=Low power 1 NoiseProtect Noise protection setting 0=Off; 1=On 1
KeyNThreshold Trigger threshold 10~64 The smaller the value, the more sensitive.
Refer to the Operating Description chapter.
IO_TOUCH_ATTR Touch key selection 0=Off; 1=On Select according to actual application requirements.
WAKEUP_ATTR Wake-up key selection 0=Off; 1=On Select according to actual application requirements.
Table 2
Considerations for Use
1. The touch parameters listed in Table 2 can be adjusted in TKS_GLOBE_VARIES.INC.
2. The main parameters that affect the battery life of the product include SystemClock, PowerSave,
MainFrequency and HaltTouchScanRate, etc. Users should properly configure these parameters
according to their requirements.
3. Since the software package adopts a time-shared multi-work scheme, the touch response will be
delayed if the user program is executed for too long a time. It is recommended that the execution
time of the USER_PROGRAM does not exceed 10ms.
Used Resources
The used RAM and ROM sources are as follows. ROM Total Size : 16384 [4000h] Total Used : 2606 [0A2Eh] Total Remain : 13778 [35D2h] Total Percentage : 15% RAM Total Size : 2304 [0900h] Total Used : 247 [00F7h]
Touch Key LCD Display Card Reference Design
WAS-19C1EN V1.00 10 / 11 September 25, 2020
Operating Description
This solution provides functions for touch key sensitivity configuration, malfunction test,
measurement for 1-key wake-up standby current and scan current.
Touch Key Sensitivity Configuration and Malfunction Test The trigger threshold of each touch key can be configured in the program to adjust the touch
sensitivity.
1. If the thickness of the PCB board is 0.4mm, the recommended trigger threshold (KeynThreshold)
is “32”.
2. If the thickness of the PCB board is 0.15mm, the recommended trigger threshold (KeynThreshold)
is “16”.
In display card applications, due to factors such as the PCB board, a too high trigger threshold
configuration could cause poor sensitivity while a too low configuration will make the product too
sensitive and therefore easy to malfunction. Developers need to pay special attention to these areas
during debugging.
The PCB front and back sides adopt mesh grounding for isolation to avoid accidental touch or
interference. Users can use a key or other metal to test malfunctions.
Test Data
Current Measurement
In this solution, the system frequency is set to 4MHz and the touch key oscillator frequency is set to
3MHz. It has also distinguished between the 1-key standby wake-up current and the all touch key
scanned current. As the standby current of the ultra-low power series of MCU is extremely small, it is
recommended to use the KEYSIGHT 34461A 61/2 ammeter when conducting measurements to avoid
measurement errors. Refer to Table 3.
Test Item Test Condition VDD Specification Measured Value
ISTB In the standby mode, scan the touch key every 256ms 3V Typ. = 200nA
Max. = 250nA 127nA
IDD Under normal operation 3V N/A 695µA
Table 3
Note: The values are measured using the KEYSIGHT 34461A 61/2 ammeter.
Conclusion
This text has used the BS67F2563 MCU to introduce the Holtek touch key LCD display card
solution. The BS67F2563 provides an excellent ultra-low 1-key standby current of 127nA@3V,
allowing for a battery life as long as 3~5 years. The integrated touch keys and C-type LCD driver
circuits in the BS67F2563 further reduce the cost of the solution, making it very suitable for battery
applications such as display cards.
Touch Key LCD Display Card Reference Design
WAS-19C1EN V1.00 11 / 11 September 25, 2020
Reference Material
Reference file: BS67F2563 Datasheet.
For more information, refer to the Holtek official website: www.holtek.com.
Versions and Modification Information
Date Author Issue 2020.06.03 黃啓德 V1.00
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