我们可以通过修改PN532库中的代码来解决这个问题。首先，我们需要打开PN532库中的PN532.cpp文件，并找到以下命令：

pn532_packetbuffer[0] = PN532_COMMAND_INDATAEXCHANGE;
pn532_packetbuffer[1] = 1; // Card number
pn532_packetbuffer[2] = 0x30; // TT2 protocol
pn532_packetbuffer[3] = 0x01; // Tmplt: "short frame"

if (pn532.tgSetData(pn532_packetbuffer, 4)) {
  return 0;
}

将这段代码替换为以下代码：

pn532_packetbuffer[0] = PN532_COMMAND_INLISTPASSIVETARGET;
pn532_packetbuffer[1] = 1; // max 1 cards at once (we can set this to 2 later)
pn532_packetbuffer[2] = 0x00; // logical starting point (lowest byte)
pn532_packetbuffer[3] = 0x00; // logical starting point (highest byte, if > 0xff)
pn532.packetPointer = 0;
pn532_packetbuffer[4] = 0x04;
pn532_packetbuffer[5] = 0x00;
pn532_packetbuffer[6] = 0x00;
pn532_packetbuffer[7] = 0x00;
pn532_packetbuffer[8] = 0x00;

if (pn532.sendCommandCheckAck(pn532_packetbuffer, 9, 1000)) {
  return 0;
}

if (pn532_packetbuffer[0] != 1) {
  return 0;
}

uint16_t sens_res = pn532_packetbuffer[2];
sens_res <<= 8;
sens_res |= pn532_packetbuffer[3];

uint8_t sel_res = pn532_packetbuffer[4];

uint8_t uid_len = pn532_packetbuffer[7];
if (uid_len > 7) {
  uid_len = 7;
}

for (uint8_t i = 0; i < uid_len; i++) {
  uid[i] = pn532_packetbuffer[8 + i];
}

这段代码将PN532设置为读取被动目标卡片的状态，并返回卡片的UID。

接下来，在我们的主程序中，我们可以使用以下命令来读取卡的UID：

uint8_t success;
uint8_t uid[] = { 0, 0, 0, 0, 0, 0, 0 };