diff --git a/libnfc/drivers/arygon.c b/libnfc/drivers/arygon.c
index f16e98a..378d352 100644
--- a/libnfc/drivers/arygon.c
+++ b/libnfc/drivers/arygon.c
@@ -177,9 +177,8 @@ arygon_connect (const nfc_device_desc_t * pndd)
   CHIP_DATA (pnd)->io = &arygon_tama_io;
   // Timer stops only after 5 bits are received => 5*128 cycles
   // When sent ...ZY (cmd ends with logical 0):
-  // TODO: calibration
-  // 50: empirical tuning
-  CHIP_DATA (pnd)->timer_correction_zy = 50 - (5 * 128);
+  // 46: empirical tuning
+  CHIP_DATA (pnd)->timer_correction_zy = 46 - (5 * 128);
   // When sent ...YY (cmd ends with logical 1):
   // a ...ZY signal finishes 64us later than a ...YY signal
   CHIP_DATA (pnd)->timer_correction_yy = CHIP_DATA (pnd)->timer_correction_zy + 64;
diff --git a/libnfc/drivers/pn532_uart.c b/libnfc/drivers/pn532_uart.c
index 4d1f24f..f8e7c12 100644
--- a/libnfc/drivers/pn532_uart.c
+++ b/libnfc/drivers/pn532_uart.c
@@ -162,9 +162,8 @@ pn532_uart_connect (const nfc_device_desc_t * pndd)
   CHIP_DATA(pnd)->io = &pn532_uart_io;
   // Timer stops only after 5 bits are received => 5*128 cycles
   // When sent ...ZY (cmd ends with logical 0):
-  // TODO: calibration
-  // 50: empirical tuning
-  CHIP_DATA (pnd)->timer_correction_zy = 50 - (5 * 128);
+  // 48: empirical tuning
+  CHIP_DATA (pnd)->timer_correction_zy = 48 - (5 * 128);
   // When sent ...YY (cmd ends with logical 1):
   // a ...ZY signal finishes 64us later than a ...YY signal
   CHIP_DATA (pnd)->timer_correction_yy = CHIP_DATA (pnd)->timer_correction_zy + 64;