STM32 电容触摸屏I2C转USB实现
最近有个需求要把一个电容式触摸屏转为标准USB HID TP设备，同时需要把TP数据通过串口输出到MCU。市面方案大多采用CH554E做I2C USB转换，没有多余的UART口。问了几家供应商都说做不了，只好自己搞了。
能偷懒就偷懒，下载USBlyzer，把原屏的ReportDescriptor抓下来直接用了：
然后跟供应商要到接口文档和初始化寄存器配置：
配置ConfigDescriptor：
用USBlyzer抓了下触摸数据：
与ReportDescriptor一致
| Usage (Finger) | 09 22 |
| Collection (Logical) | A1 02 |
| Usage (Tip Switch) | 09 42 |
| Logical Minimum (0) | 15 00 |
| Logical Maximum (1) | 25 01 |
| Report Size (1) | 75 01 |
| Report Count (1) | 95 01 |
| Input (Data,Var,Abs,NWrp,Lin,Pref,NNul,Bit) | 81 02 |
| Report Count (1) | 95 01 |
| Input (Cnst,Var,Abs,NWrp,Lin,Pref,NNul,Bit) | 81 03 |
| Report Count (6) | 95 06 |
| Input (Cnst,Var,Abs,NWrp,Lin,Pref,NNul,Bit) | 81 03 |
| Report Size (8) | 75 08 |
| Usage (Contact Identifier) | 09 51 |
| Report Count (1) | 95 01 |
| Input (Data,Var,Abs,NWrp,Lin,Pref,NNul,Bit) | 81 02 |
| Usage Page (Generic Desktop) | 05 01 |
| Logical Maximum (2048) | 26 00 08 |
| Report Size (16) | 75 10 |
| Unit Exponent (-2) | 55 0E |
| Unit (SI Lin: Length (cm)) | 65 11 |
| Usage (X) | 09 30 |
| Physical Minimum (0) | 35 00 |
| Physical Maximum (2169) | 46 79 08 |
| Report Count (1) | 95 01 |
| Input (Data,Var,Abs,NWrp,Lin,Pref,NNul,Bit) | 81 02 |
| Physical Minimum (1) | 35 01 |
| Physical Minimum (0) | 35 00 |
| Physical Maximum (1356) | 46 4C 05 |
| Logical Maximum (2048) | 26 00 08 |
| Usage (Y) | 09 31 |
| Input (Data,Var,Abs,NWrp,Lin,Pref,NNul,Bit) | 81 02 |
| Physical Minimum (1) | 35 01 |
| Physical Minimum (0) | 35 00 |
| Usage Page (Digitizer) | 05 0D |
| Logical Maximum (255) | 26 FF 00 |
| Physical Maximum (255) | 46 FF 00 |
| Report Count (1) | 95 01 |
| Usage (Width) | 09 48 |
| Input (Data,Var,Abs,NWrp,Lin,Pref,NNul,Bit) | 81 02 |
| End Collection | C0 |
把TP的I2C接口调好就OK了，测试了一下OK。
下一步是把程序移植到STM32F070，价格不错，比汇顶提供的CH554还要便宜！