SDHC SPI 写入问题
我一直在尝试使用 LPC1766 SPI 外围设备有一段时间了，现在我陷入了一个问题，我在任何地方都找不到答案。
问题是：SDHC 卡未按预期响应写入和读取命令。
基于 Chan 的流程图和 NXP 应用笔记的初始化一切正常。我可以区分卡片版本，读取 OCR、CID、CSD 并确定它们的大小。
在这一步之后，我开始每秒写入单个块并将其读回以检查数据完整性。在金士顿 SDHC 4GB Class 4 卡上，我可以发送第一个写入命令，但在第二个命令上，该卡甚至不向 CMD24 应答（0x00 或 0x01）。使用 SanDisk 4GB Class 4 卡，结果有所不同，每个命令都由卡应答，但读回数据时我只得到零（我确信我没有写零）。如果我使用 SDSC 卡，一切正常。
我知道 SDHC 是块寻址而不是字节寻址，并且我需要为 SDHC 发送带有 CCS 的 ACMD41。我还知道时钟频率不是问题（使用 400KHz 启动，然后使用 20MHz 写入/读取），因为我刚刚打开 CRC 检查，并且所有卡都在接受命令和数据。如果我停止计算 CRC，所有卡都会拒绝命令和数据。
I've been trying to do an SD card interface with the LPC1766 SPI peripheral for a while and right now I'm stuck in a problem that I couldn't find the answer anywhere.
The problem is: SDHC cards are not responding to write and read commands as expected.
Everything works fine on the initialization that was based on Chan's flowchart and on an NXP application note. I can differentiate the cards versions, read the OCR, CID, CSD and determine their sizes.
After that step I start writing single blocks every one second and reading it back to check the data integrity. On a Kingston SDHC 4 GB Class 4 card I can send a first write command but on the second one the card does not even answer (0x00 or 0x01) to the CMD24. With a SanDisk 4 GB Class 4 card the results are different, every command is answered by the card, but I get only zeroes when reading the data back (I'm sure I'm not writing zeroes). If I use SDSC cards, everything works fine.
I'm aware that SDHC are block addressed and not byte addressed and that I need to send ACMD41 with the CCS on for SDHC. I also know that the clock frequency is not an issue (using 400 KHz to start and then 20 MHz to write/read), because I just turned on the CRC checking and all cards are accepting the commands and data. If I stop calculating the CRC all cards reject commands and data.
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如何连接 SD 卡？根据模式/状态，SD(HC) 卡需要一个外部上拉电阻。如果没有它，你读到的为零，所以这可能是你的问题。
How do you connect your SD card? Depending on the mode/state the SD(HC) card needs an external pull-up resistor. Without that you read zero, so that may be your problem.