From 7be3c7fdf15d220026c744e395b349f31a080cd5 Mon Sep 17 00:00:00 2001
From: Antoine van Gelder <antoine@greatscottgadgets.com>
Date: Tue, 9 Dec 2025 10:21:56 +0200
Subject: [PATCH] firmware: add support for setting max2831 rx hpf corner
 frequency

---
 firmware/common/max2831.c | 28 ++++++++++++++++++++++++++--
 firmware/common/max2831.h | 12 ++++++++++++
 2 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/firmware/common/max2831.c b/firmware/common/max2831.c
index a8a44f45..15b14bdb 100644
--- a/firmware/common/max2831.c
+++ b/firmware/common/max2831.c
@@ -380,15 +380,39 @@ bool max2831_set_vga_gain(max2831_driver_t* const drv, const uint32_t gain_db) {
 	if( (gain_db & 0x1) || gain_db > 62) {/* 0b11111*2 */
 		return false;
 	}
-	
+
 	set_MAX2831_RXVGA_GAIN(drv, (gain_db >> 1) );
 	max2831_reg_commit(drv, 11);
 	return true;
 }
 
-bool max2831_set_txvga_gain(max2831_driver_t* const drv, const uint32_t gain_db) {	
+bool max2831_set_txvga_gain(max2831_driver_t* const drv, const uint32_t gain_db) {
 	uint16_t value = MIN((gain_db << 1) | 1, 0x3f);
 	set_MAX2831_TXVGA_GAIN(drv, value);
 	max2831_reg_commit(drv, 12);
 	return true;
 }
+
+void max2831_set_rx_hpf_frequency(max2831_driver_t* const drv, const max2831_rx_hpf_freq_t freq)
+{
+	/**
+	 * Frequency     RXHP     RX_HPF_SEL (D13:D12)
+	 *
+	 *   100  Hz     low      00
+	 *     4 kHz     low      x1
+	 *    30 kHz     low      10
+	 *   600 kHz     high     xx
+	 */
+	switch (freq) {
+	case MAX2831_RX_HPF_100_HZ:
+	case MAX2831_RX_HPF_4_KHZ:
+	case MAX2831_RX_HPF_30_KHZ:
+		set_MAX2831_RX_HPF_SEL(drv, freq);
+		max2831_reg_commit(drv, 7);
+		gpio_clear(drv->gpio_rxhp);
+		break;
+	case MAX2831_RX_HPF_600_KHZ:
+		gpio_set(drv->gpio_rxhp);
+		break;
+	}
+}
diff --git a/firmware/common/max2831.h b/firmware/common/max2831.h
index 4279cbc8..033b590e 100644
--- a/firmware/common/max2831.h
+++ b/firmware/common/max2831.h
@@ -41,6 +41,13 @@ typedef enum {
 	MAX2831_MODE_RX_CALIBRATION,
 } max2831_mode_t;
 
+typedef enum {
+	MAX2831_RX_HPF_100_HZ = 0,
+	MAX2831_RX_HPF_4_KHZ = 1,
+	MAX2831_RX_HPF_30_KHZ = 2,
+	MAX2831_RX_HPF_600_KHZ = 3,
+} max2831_rx_hpf_freq_t;
+
 struct max2831_driver_t;
 typedef struct max2831_driver_t max2831_driver_t;
 
@@ -91,6 +98,11 @@ bool max2831_set_lna_gain(max2831_driver_t* const drv, const uint32_t gain_db);
 bool max2831_set_vga_gain(max2831_driver_t* const drv, const uint32_t gain_db);
 bool max2831_set_txvga_gain(max2831_driver_t* const drv, const uint32_t gain_db);
 
+/* Set receiver high-pass filter corner frequency in Hz */
+extern void max2831_set_rx_hpf_frequency(
+	max2831_driver_t* const drv,
+	const max2831_rx_hpf_freq_t freq);
+
 extern void max2831_tx(max2831_driver_t* const drv);
 extern void max2831_rx(max2831_driver_t* const drv);
 extern void max2831_tx_calibration(max2831_driver_t* const drv);