From 10e8b0d9344b90a3244766e178bb7daaa19a5962 Mon Sep 17 00:00:00 2001
From: Michael Ossmann <mike@ossmann.com>
Date: Tue, 30 Dec 2025 20:35:25 -0500
Subject: [PATCH] Decimate automatically in RX and RX sweep modes

---
 firmware/common/hackrf_core.c |  3 +++
 firmware/common/radio.c       | 29 +++++++++++++++++++++++++++++
 firmware/common/radio.h       |  6 ++++++
 3 files changed, 38 insertions(+)

diff --git a/firmware/common/hackrf_core.c b/firmware/common/hackrf_core.c
index 23868b0f..fdaecf2b 100644
--- a/firmware/common/hackrf_core.c
+++ b/firmware/common/hackrf_core.c
@@ -376,6 +376,9 @@ radio_t radio = {
 					.clock[RADIO_CLOCK_CLKIN] = {.enable = false},
 					.clock[RADIO_CLOCK_CLKOUT] = {.enable = false},
 					.trigger_enable = false,
+#ifdef PRALINE
+					.resampling_n = 0,
+#endif
 				},
 			.clock_source = CLOCK_SOURCE_HACKRF,
 		},
diff --git a/firmware/common/radio.c b/firmware/common/radio.c
index d0cfed70..5f323a13 100644
--- a/firmware/common/radio.c
+++ b/firmware/common/radio.c
@@ -52,7 +52,36 @@ radio_error_t radio_set_sample_rate(
 		return RADIO_OK;
 	}
 
+#ifdef PRALINE
+	#define MAX_AFE_RATE 40000000
+	#define MAX_N        5
+	uint8_t n = 0; // resampling ratio is 2**n
+	if ((config->mode == TRANSCEIVER_MODE_RX) ||
+	    (config->mode == TRANSCEIVER_MODE_RX_SWEEP)) {
+		n = 1;
+		uint32_t afe_rate_x2 = 2 * sample_rate.hz;
+		while ((afe_rate_x2 <= MAX_AFE_RATE) && (n < MAX_N)) {
+			afe_rate_x2 <<= 1;
+			n++;
+		}
+		fpga_set_rx_decimation_ratio(&fpga, n);
+	}
+	config->resampling_n = n;
+	bool ok = sample_rate_frac_set(sample_rate.num << n, sample_rate.div);
+	if (ok) {
+		config->sample_rate[element] = sample_rate;
+		radio_channel_t* channel = &radio->channel[chan_id];
+		radio_frequency_t frequency =
+			radio_get_frequency(radio, channel->id, RADIO_FREQUENCY_RF);
+		ok = radio_set_frequency(
+			radio,
+			channel->id,
+			RADIO_FREQUENCY_RF,
+			frequency);
+	}
+#else
 	bool ok = sample_rate_frac_set(sample_rate.num, sample_rate.div);
+#endif
 	if (!ok) {
 		return RADIO_ERR_INVALID_PARAM;
 	}
diff --git a/firmware/common/radio.h b/firmware/common/radio.h
index 83ff6134..2b054bd2 100644
--- a/firmware/common/radio.h
+++ b/firmware/common/radio.h
@@ -156,6 +156,12 @@ typedef struct {
 
 	// currently active transceiver mode
 	transceiver_mode_t mode;
+
+#ifdef PRALINE
+	// resampling ratio is 2**n
+	uint8_t resampling_n;
+#endif
+
 } radio_config_t;
 
 typedef struct radio_channel_t {