From c63cc16bb5ab99550197093b046635032bbdb21b Mon Sep 17 00:00:00 2001
From: Niel Nielsen <nieldk@gmail.com>
Date: Fri, 1 May 2026 17:50:32 +0200
Subject: [PATCH] Add files via upload

---
 .../src/rfid/nfctag/lf/lf_tag_em.c            | 54 +++++++------------
 1 file changed, 20 insertions(+), 34 deletions(-)

diff --git a/firmware/application/src/rfid/nfctag/lf/lf_tag_em.c b/firmware/application/src/rfid/nfctag/lf/lf_tag_em.c
index 2a83193..5c66d12 100644
--- a/firmware/application/src/rfid/nfctag/lf/lf_tag_em.c
+++ b/firmware/application/src/rfid/nfctag/lf/lf_tag_em.c
@@ -43,7 +43,7 @@ static void lf_field_lost(void) {
     g_is_tag_emulating = false;  // Reset the flag in the emulation
     m_is_lf_emulating = false;
     TAG_FIELD_LED_OFF()  // Make sure the indicator light of the LF field status
-    NRF_LPCOMP->INTENSET = LPCOMP_INTENCLR_CROSS_Msk | LPCOMP_INTENCLR_UP_Msk | LPCOMP_INTENCLR_DOWN_Msk | LPCOMP_INTENCLR_READY_Msk;
+    // LPCOMP stays enabled (DETECT_CROSS) — no INTENSET/INTENCLR needed.
     // call sleep_timer_start *after* unsetting g_is_tag_emulating
     sleep_timer_start(SLEEP_DELAY_MS_FIELD_125KHZ_LOST);  // Start the timer to enter the sleep
     NRF_LOG_INFO("LF FIELD LOST");
@@ -68,35 +68,29 @@ bool is_lf_field_exists(void) {
  * priority is set to APP_IRQ_PRIORITY_HIGH).
  */
 static void lpcomp_event_handler(nrf_lpcomp_event_t event) {
-    // Only when the lf -frequency emulation is not launched, and the analog card is started
-    if (m_is_lf_emulating || event != NRF_LPCOMP_EVENT_UP) {
-        return;
+    if (!m_is_lf_emulating && event == NRF_LPCOMP_EVENT_UP) {
+        // Field appeared — start continuous looping broadcast.
+        // LPCOMP stays enabled so the DOWN event stops us when field is lost.
+        sleep_timer_stop();
+        m_is_lf_emulating = true;
+        g_is_tag_emulating = true;
+        g_usb_led_marquee_enable = false;
+        set_slot_light_color(RGB_BLUE);
+        TAG_FIELD_LED_ON()
+        nrfx_pwm_simple_playback(&m_broadcast, m_pwm_seq, 1, NRFX_PWM_FLAG_LOOP);
+        NRF_LOG_INFO("LF FIELD DETECTED");
+    } else if (m_is_lf_emulating && event == NRF_LPCOMP_EVENT_DOWN) {
+        // Field dropped during emulation — stop PWM; pwm_handler will clean up.
+        nrfx_pwm_stop(&m_broadcast, false);
+        NRF_LOG_INFO("LF FIELD LOST (LPCOMP DOWN)");
     }
-
-    sleep_timer_stop();  // turn off dormant delay
-    nrfx_lpcomp_disable();
-
-    // set the emulation status logo bit
-    m_is_lf_emulating = true;
-    g_is_tag_emulating = true;
-    // turn off USB light effect when emulating cards
-    g_usb_led_marquee_enable = false;
-
-    // LED status update
-    set_slot_light_color(RGB_BLUE);
-    TAG_FIELD_LED_ON()
-
-    // use precise hardware timer to broadcast card id
-    nrfx_pwm_simple_playback(&m_broadcast, m_pwm_seq, LF_125KHZ_BROADCAST_MAX, NRFX_PWM_FLAG_STOP);
-
-    NRF_LOG_INFO("LF FIELD DETECTED");
 }
 
 static void lpcomp_init(void) {
     nrfx_lpcomp_config_t cfg = NRFX_LPCOMP_DEFAULT_CONFIG;
     cfg.input = LF_RSSI;
     cfg.hal.reference = NRF_LPCOMP_REF_SUPPLY_1_16;
-    cfg.hal.detection = NRF_LPCOMP_DETECT_UP;
+    cfg.hal.detection = NRF_LPCOMP_DETECT_CROSS;
     cfg.hal.hyst = NRF_LPCOMP_HYST_50mV;
 
     ret_code_t err_code = nrfx_lpcomp_init(&cfg, lpcomp_event_handler);
@@ -104,21 +98,13 @@ static void lpcomp_init(void) {
 }
 
 static void pwm_handler(nrfx_pwm_evt_type_t event_type) {
+    // In LOOP mode this only fires when nrfx_pwm_stop() is called explicitly
+    // (triggered by LPCOMP DOWN event when field is lost).
     if (event_type != NRFX_PWM_EVT_STOPPED) {
         return;
     }
-
-    // after last broadcast, force NO_MOD on antenna to measure field.
     ANT_NO_MOD();
-    bsp_delay_ms(1);
-    // We don't need any events, but only need to detect the state of the field
-    NRF_LPCOMP->INTENCLR = LPCOMP_INTENCLR_CROSS_Msk | LPCOMP_INTENCLR_UP_Msk | LPCOMP_INTENCLR_DOWN_Msk | LPCOMP_INTENCLR_READY_Msk;
-    if (is_lf_field_exists()) {
-        nrfx_lpcomp_disable();
-        nrfx_pwm_simple_playback(&m_broadcast, m_pwm_seq, LF_125KHZ_BROADCAST_MAX, NRFX_PWM_FLAG_STOP);
-    } else {
-        lf_field_lost();
-    }
+    lf_field_lost();
 }
 
 static void pwm_init(void) {