Fix PN532 SPI communication (#1511)

esphome/components/pn532_spi/pn532_spi.cpp

@@ -26,7 +26,7 @@ bool PN532Spi::write_data(const std::vector<uint8_t> &data) {
   delay(2);
   // First byte, communication mode: Write data
   this->write_byte(0x01);
-
+  ESP_LOGV(TAG, "Writing data: %s", hexencode(data).c_str());
   this->write_array(data.data(), data.size());
   this->disable();
 
@@ -34,31 +34,122 @@ bool PN532Spi::write_data(const std::vector<uint8_t> &data) {
 }
 
 bool PN532Spi::read_data(std::vector<uint8_t> &data, uint8_t len) {
-  this->enable();
-  // First byte, communication mode: Read state
-  this->write_byte(0x02);
+  ESP_LOGV(TAG, "Waiting for ready byte...");
 
   uint32_t start_time = millis();
   while (true) {
-    if (this->read_byte() & 0x01)
+    this->enable();
+    // First byte, communication mode: Read state
+    this->write_byte(0x02);
+    bool ready = this->read_byte() == 0x01;
+    this->disable();
+    if (ready)
       break;
+    ESP_LOGV(TAG, "Not ready yet...");
 
     if (millis() - start_time > 100) {
-      this->disable();
       ESP_LOGV(TAG, "Timed out waiting for readiness from PN532!");
       return false;
     }
+    yield();
   }
 
   // Read data (transmission from the PN532 to the host)
+  this->enable();
+  delay(2);
   this->write_byte(0x03);
 
+  ESP_LOGV(TAG, "Reading data...");
+
   data.resize(len);
   this->read_array(data.data(), len);
   this->disable();
   data.insert(data.begin(), 0x01);
+  ESP_LOGV(TAG, "Read data: %s", hexencode(data).c_str());
   return true;
-};
+}
+
+bool PN532Spi::read_response(uint8_t command, std::vector<uint8_t> &data) {
+  ESP_LOGV(TAG, "Reading response");
+
+  uint32_t start_time = millis();
+  while (true) {
+    this->enable();
+    // First byte, communication mode: Read state
+    this->write_byte(0x02);
+    bool ready = this->read_byte() == 0x01;
+    this->disable();
+    if (ready)
+      break;
+    ESP_LOGV(TAG, "Not ready yet...");
+
+    if (millis() - start_time > 100) {
+      ESP_LOGV(TAG, "Timed out waiting for readiness from PN532!");
+      return false;
+    }
+    yield();
+  }
+
+  this->enable();
+  delay(2);
+  this->write_byte(0x03);
+
+  std::vector<uint8_t> header(7);
+  this->read_array(header.data(), 7);
+
+  ESP_LOGV(TAG, "Header data: %s", hexencode(header).c_str());
+
+  if (header[0] != 0x00 && header[1] != 0x00 && header[2] != 0xFF) {
+    // invalid packet
+    ESP_LOGV(TAG, "read data invalid preamble!");
+    return false;
+  }
+
+  bool valid_header = (static_cast<uint8_t>(header[3] + header[4]) == 0 &&  // LCS, len + lcs = 0
+                       header[5] == 0xD5 &&        // TFI - frame from PN532 to system controller
+                       header[6] == command + 1);  // Correct command response
+
+  if (!valid_header) {
+    ESP_LOGV(TAG, "read data invalid header!");
+    return false;
+  }
+
+  // full length of message, including command response
+  uint8_t full_len = header[3];
+  // length of data, excluding command response
+  uint8_t len = full_len - 1;
+  if (full_len == 0)
+    len = 0;
+
+  ESP_LOGV(TAG, "Reading response of length %d", len);
+
+  data.resize(len + 1);
+  this->read_array(data.data(), len + 1);
+  this->disable();
+
+  ESP_LOGV(TAG, "Response data: %s", hexencode(data).c_str());
+
+  uint8_t checksum = header[5] + header[6];  // TFI + Command response code
+  for (int i = 0; i < len - 1; i++) {
+    uint8_t dat = data[i];
+    checksum += dat;
+  }
+  checksum = ~checksum + 1;
+
+  if (data[len - 1] != checksum) {
+    ESP_LOGV(TAG, "read data invalid checksum! %02X != %02X", data[len - 1], checksum);
+    return false;
+  }
+
+  if (data[len] != 0x00) {
+    ESP_LOGV(TAG, "read data invalid postamble!");
+    return false;
+  }
+
+  data.erase(data.end() - 2, data.end());  // Remove checksum and postamble
+
+  return true;
+}
 
 void PN532Spi::dump_config() {
   PN532::dump_config();

esphome/components/pn532_spi/pn532_spi.h

@@ -18,6 +18,7 @@ class PN532Spi : public pn532::PN532,
  protected:
   bool write_data(const std::vector<uint8_t> &data) override;
   bool read_data(std::vector<uint8_t> &data, uint8_t len) override;
+  bool read_response(uint8_t command, std::vector<uint8_t> &data) override;
 };
 
 }  // namespace pn532_spi