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在PIC18F25K80上的ADC端口上读取0V似乎在我尝试过的大多数设备上给出了7到10之间的值。我已经尝试将AN2设置为VREF—连接到地上。我已经尝试将VSS设置为VREF-。我仍然获得高偏移值而不是零。ADC（对一些EN批准的运行时间要求）我必须用一个词，并且每一个ADC在它上面读，并且希望它是零。通常我希望ADC地读有一点噪声，可能是0闪烁到1或甚至2：即比特0和1。这通常是可以的，因为忽略一个或两个。精度可以正常地落在传感器/换能器被认可的误差范围内，但是用2位甚至3套来获得地面读数是不可接受的。/ DeVICEDOC/PIC18F66 K80-硅误差数据片澄清-800，519P，但是…有没有办法？不管怎样，内部读取ADC以证明它没有停留在位上吗？是否有一个内部寄存器，如温度二极管或带隙，内部连接，以读取零？
以上来自于百度翻译 以下为原文 Reading 0V on an ADC port on the PIC18F25K80 seems to give a value between 7 and 10 on most devices I have tried. I have tried setting AN2 as vref- connected to ground. I have tried setting Vss as the vref-. I still get the high offset values instead of zero. In order to ensure no stuck at bits in the ADC ( a run time requirement for some EN approvals) I have had to take a word and AND every ADC read on it and *hope* it zeros. Normally I would expect a little noise on an ADC ground reading, maybe a 0 flickering to a 1 or even a 2: i.e. bits 0 and 1. This is generally OK because ignoring one or two bits of accuracy normally can fall with an acceptable error margin for the sensor/transducer being approved. But getting GROUND readings with bits 2 and even 3 set is not going to be acceptable. The erratta does say pm 30 ADC counts which acknowledges the problem. http://ww1.microchip.com/downloa ... ation-80000519P.pdf BUT.... Is there any way around this ? Is there anyway to internally read the ADC to demonstrate it does not have stuck at bits? Is there an internal AN register that, like the temp diode or bandgap, connects internally to read a ZERO ? 
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一个扫描似乎是（如预期的）在模32上的重复结果。未连接的数字似乎读回0x00 D作为一个值。还有什么方法可以证明ADC能够返回零点（即没有卡在1位）吗？
以上来自于百度翻译 以下为原文 Putting a sweep in seems to (as expected) repeat results on modulo 32. Unconnected AN numbers seem to read back 0x00D as a value. What other way could I prove the ADC is capable of returning zeros (i.e. has no stuck at 1 bits)? #define ADC_TEST 1 #if ( ADC_TEST == 1) { int adc_res[64]; int i,adc; for (i=0; i<64;i++) { adc_res = adc = read_analog_input(i); asm("t nop"); asm("t nop"); } } #endif |
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在询问论坛之前阅读数据表和勘误表。
以上来自于百度翻译 以下为原文 Read the datasheet and errata prior to asking the forum. |
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Mbedder：是的。我所拥有的设备（Rev 6）并不像ErraTATA所建议的那样糟糕，但仍然很难在这里询问是否有人能绕过这个问题。如果ADC不能读取它自己的接地并使它返回零，那么它就不是好兆头。
以上来自于百度翻译 以下为原文 Mbedder: I did. The devices I have (rev 6) do not behave as badly as the erratta suggests but still badly enough to ask here if anyone has got any way around this. It does not bode well if the ADC cannot read its own ground and give you back zero. |
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只需按照勘误表或使用不同的PIC模型的解决方案建议。
以上来自于百度翻译 以下为原文 Just follow the workaround suggestions as per the errata sheet or use different PIC model. |
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顺便说一句，如果你找到任何具有零ADC偏移的MCU，请让我们知道，因为“DAS是VistasTiCH”。
以上来自于百度翻译 以下为原文 BTW if you find any MCU with zero ADC offset - let us know because "das ist fantastisch" |
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嗨，PIC18中的“旧”12位ADC有几个问题。最新的设备有一个“新”的12位ADC，它似乎已经纠正了几个问题，特别是偏移误差。我认为可以用它的继任者PIC18F25K83-取代PIC18F25K80（可能是PIN到PIN），但是需要一些SW改变。它是STI。目前，ADC偏移被指定为6 LSB MAX和0.5 LSB TYP，这比当前一个更好。
以上来自于百度翻译 以下为原文 Hi, The "old" 12bits ADC in PIC18 had several issues. Newest devices have a "new" 12bits ADC which seems to have corrected several issues, in particular the offset error. I think you can replace PIC18F25K80 by its successor PIC18F25K83 (probably pin to pin) but some SW changes will be needed. It is still preliminary but currently, ADC offset is specified as 6 LSB MAX and 0.5 LSB typ, so much better than current one. Regards |
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在设备上没有AVDD/AVSS引脚。ADC只能读取其自己的接地或任何地面参考信号的近似值，这取决于电路板布局以及其他外围设备在VSS引脚中倾倒的电流。
以上来自于百度翻译 以下为原文 There are no Avdd/AVss pins on the device. The ADC can only read an approximation of its own ground or any ground referenced signal, depending on board layout and how much current other peripherals are dumping into the Vss pin. |
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