AN3236 STM8应用笔记 触摸按键设计(英文)
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November 2013DocID17613 Rev 21/15
AN3236
Application note
Guidelines to increase the number of touch sensing touchkeys Introduction
The touch sensing libraries allow management of the following number of channels depending on the targeted device series :
∙
up to 24 channels when using devices from the STM32F0 and STM32F3 series.∙
up to 34 channels when using devices from the STM32L1 series.∙
up to 6 channels when using devices from the STM8L101 lines.∙
up to 20 channels when using devices from the STM8L151/152 and the STM8L162 lines.∙up to 24 channels when using devices from the STM8S and STM8AF series.
The guidelines detailed into this document aim to help designers to overcome channel number limitation. They describe tips and tricks to increase the number of touchkeys and/or to create a touchkey matrix by keeping the same targetted device.Table 1. Applicable products
Type
Applicable products Microcontrollers STM32F0 series, STM32F3 series, STM32L1 series, STM8L101 lines,
STM8L151/152 lines, STM8L162 lines, STM8S series, STM8AF series.
Contents AN3236
Contents
1Adding an extra touchkey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1Basic hardware implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.2Software implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.3Limitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2Combined implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3Touchkey matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.1Matrix hardware implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.2Software implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.3Limitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 4Maximizing the number of touchkeys . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5Working around the limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.1Touchkeys set definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.2Detection exclusion system (DxS) usage . . . . . . . . . . . . . . . . . . . . . . . . . 13 6Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 7Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2/15DocID17613 Rev 2