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测钻笔是通过什么原理测量硬度的
- 2021-01-24
测钻笔是专门为鉴定钻石及其仿制品而设计的一种仪器，宝石中热导率最高的为钻石，在室温下钻石的热导率从Ⅰ型的100W/（m℃）变化到Ⅱa型的2600W/（m℃） 次高的为刚玉，其40W/（m℃）。近年来出现的合成碳硅石其热导率高，仅次于钻石在该仪器下也有反应。测钻笔正是利用钻石这一热学性质来鉴定钻石及其除合成碳硅石以外的钻石的仿制品。操作较方便，结果较直观。测钻笔由测头与控制盒组成，测头的金属尖端为电加热，当加热的金属尖端触探钻石表面时，温度明显下降，电热传感会发出蜂鸣声。
没有一种变压器可以直接把交流变为直流呢？
- 2021-01-24
Transformer does not covert Ac to DC or DC to Ac it only steps up or steps down the current4) diagram for 4) connect diodes like this in the form of a quadrilateralTo covert Ac to DC1) check what your AC input voltage is.2)Find the voltage and needed to power the components of your electronic device3)Use a transformer to step down the output from high-voltage AC to low-voltage AC. Electrical current enters the primary coil of the transformer and induces a current in the secondary coil which has fewer coils resulting in a lower voltage.4)Run the low-voltage AC through a rectifier. A rectifier usually consists of 4 diodes arranged in a quadrilateral shape -- a type called a bridge rectifier. A diode only allows current to pass in 1 direction; the quadrilateral configuration allow 2 diodes to pass the positive half of the current and the other 2 diodes to pass the negative half.5)Add a large electrolytic capacitor to smooth out the voltage. A capacitor stores an electrical charge for a short time and then releases it slowly. The input from the rectifier resembles a string of humps; the output of the "smoothing capacitor" is a somewhat steady voltage with ripples.For devices that only need a low current you can create a regulator with a resistor and a zener diode which is designed to break down when a certain voltage is reached allowing current to pass through it. The resistor limits the current.
手机typec怎么接usb转串口设备
- 2021-01-24
USB C转USB适配器[2-Pack]，Thunderbolt 3转USB 3.0 OTG适配器兼容MacBook Pro，Chromebook，Pixelbook，Microsoft Surface Go，Galaxy S8 S9 S10 Plus，Note 8 9，LG V35 G7 G6 Thinq，Pixel 2 3（ 灰色）
arm的atf如何与uboot结合
- 2021-01-24
ATFBuilding ATF is as follows – make sure you have set your ARCH and CROSS_COMPILE environment variables as noted above cd arm-trusted-firmware make PLAT=imx8mq bl31 cp build/imx8mq/release/bl31.bin ../u-boot/ cd .. Extract and copy firmwareExtract the NXP firmware archive and accept the end user agreement chmod +x firmware-imx-7.9.bin ./firmware-imx-7.9.bin cp firmware-imx-7.9/firmware/hdmi/cadence/signed_hdmi_imx8m.bin u-boot/ cp firmware-imx-7.9/firmware/ddr/synopsys/lpddr4*.bin u-boot/
arm的atf如何与uboot结合
- 2021-01-24
对于所有K3平台，ATF用作ARMv8-A内核上的初始起始代码。 在设置了初始核心状态并应用了所需的勘误表修复程序之后，它将自身设置为EL3监视器处理程序。 此后，将安装安全世界软件（OP-TEE）并将执行传递给非安全世界中的Linux内核或U-Boot。默认加载位置ATF image 0x70000000OP-TEE image 0x9e800000U-Boot / Linux内核映像0x80080000的DTB 0x82000000如果需要，可以在以下位置更改这些默认值：plat / ti / k3 / board / generic / board.mk
rgb屏是888接口的主板是565输出的怎么接线
- 2021-01-22
#include <stdio.h> #include <assert.h> #include <stdint.h> uint16_t rgb888torgb565(uint8_t *rgb888Pixel) { uint8_t red = rgb888Pixel[0]; uint8_t green = rgb888Pixel[1]; uint8_t blue = rgb888Pixel[2]; uint16_t b = (blue >> 3) & 0x1f; uint16_t g = ((green >> 2) & 0x3f) << 5; uint16_t r = ((red >> 3) & 0x1f) << 11; return (uint16_t) (r | g | b); } int main(void) { FILE *fb = fopen("input.rgb" "rb"); assert(fb); FILE *tmp = fopen("output.rgb565" "wb"); assert(tmp); uint8_t i[3]; while (!feof(fb)) { fread(i sizeof(uint8_t) 3 fb); uint16_t x = rgb888torgb565(i); fwrite(&x sizeof(uint16_t) 1 tmp); } fclose(fb); fclose(tmp); return 0; }
rgb屏是888接口的主板是565输出的怎么接线
- 2021-01-22
总之我还是不很清楚，不过我在知乎上面找到一篇相关的文章，你可以参考 https://zhuanlan.zhihu.com/p/111272839