diff --git a/armsrc/i2c.c b/armsrc/i2c.c
index 52d1a64b4..edb4a3487 100644
--- a/armsrc/i2c.c
+++ b/armsrc/i2c.c
@@ -41,10 +41,18 @@
 // cannot drift apart.
 #define I2C_DELAY_1CLK    SpinDelayUsPrecision(I2C_DELAY_1CLK_US)
 #define I2C_DELAY_2CLK    SpinDelayUsPrecision(I2C_DELAY_2CLK_US)
-#define I2C_DELAY_SDA     SpinDelayUsPrecision(I2C_DELAY_SDA_US)
+#define I2C_DELAY_SDA     SpinDelayUsPrecision(s_app_i2c_timing ? I2C_DELAY_SDA_APP_US : I2C_DELAY_SDA_US)
 #define I2C_DELAY_HOLD    SpinDelayUsPrecision(I2C_DELAY_HOLD_US)
 #define I2C_DELAY_HIGH    SpinDelayUsPrecision(I2C_DELAY_HIGH_US)
 
+static bool s_app_i2c_timing = false;
+
+bool sc_set_app_i2c_timing(bool enabled) {
+    bool previous = s_app_i2c_timing;
+    s_app_i2c_timing = enabled && I2C_APP_FAST_TIMING;
+    return previous;
+}
+
 #define SC_PROTO_T0     (1 << 0)
 #define SC_PROTO_T1     (1 << 1)
 
diff --git a/armsrc/i2c.h b/armsrc/i2c.h
index e84673c2d..52617f47b 100644
--- a/armsrc/i2c.h
+++ b/armsrc/i2c.h
@@ -82,6 +82,8 @@
 // SCL falls (spec 0.3 us) and SCL high width (spec 4 us) - so they get the
 // standard mode minimum with margin instead of a full clock.
 #define I2C_DELAY_SDA_US        15
+#define I2C_DELAY_SDA_APP_US    8
+#define I2C_APP_FAST_TIMING     1
 #define I2C_DELAY_HOLD_US       2
 #define I2C_DELAY_HIGH_US       6
 
@@ -145,6 +147,9 @@ void sc_log_trace_span(const uint8_t *d, uint16_t len, bool reader2tag, uint32_t
 void sc_log_trace_reset(void);
 
 bool sc_rx_bytes(uint8_t *dest, uint16_t *destlen, uint32_t wait);
+
+// Returns the previous app timing state.
+bool sc_set_app_i2c_timing(bool enabled);
 //
 bool GetATR(smart_card_atr_t *card_ptr, bool verbose);
 
diff --git a/armsrc/sam_sc.c b/armsrc/sam_sc.c
index 8b196174e..1f1c35e48 100644
--- a/armsrc/sam_sc.c
+++ b/armsrc/sam_sc.c
@@ -454,10 +454,12 @@ static int sam_sc_card_api_loop(uint8_t *response, uint16_t *response_len,
 }
 
 void sam_sc_handler_no_trace(const PacketCommandNG *c) {
+    const bool app_timing = sc_set_app_i2c_timing(true);
     const bool tracing = get_tracing();
     const bool blocked = set_tracing_blocked(true);
     clear_trace();
     sam_sc_handler(c);
+    sc_set_app_i2c_timing(app_timing);
     set_tracing_blocked(blocked);
     set_tracing(tracing);
 }