From e9fc3ab57030da7d293a0955f9cf841918736b48 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Thu, 5 Oct 2023 19:11:29 +1100
Subject: [PATCH] AP_BattMonitor: added SHUNT parameter to INS2xx driver

some vendors want different shunt resistors
---
 .../AP_BattMonitor/AP_BattMonitor_INA2xx.cpp     | 16 ++++++++++++----
 libraries/AP_BattMonitor/AP_BattMonitor_INA2xx.h |  1 +
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/libraries/AP_BattMonitor/AP_BattMonitor_INA2xx.cpp b/libraries/AP_BattMonitor/AP_BattMonitor_INA2xx.cpp
index 0a504132aa..aa4dabe1dd 100644
--- a/libraries/AP_BattMonitor/AP_BattMonitor_INA2xx.cpp
+++ b/libraries/AP_BattMonitor/AP_BattMonitor_INA2xx.cpp
@@ -46,6 +46,10 @@ extern const AP_HAL::HAL& hal;
 #define DEFAULT_BATTMON_INA2XX_MAX_AMPS 90.0
 #endif
 
+#ifndef DEFAULT_BATTMON_INA2XX_SHUNT
+#define DEFAULT_BATTMON_INA2XX_SHUNT 0.0005
+#endif
+
 #ifndef HAL_BATTMON_INA2XX_BUS
 #define HAL_BATTMON_INA2XX_BUS 0
 #endif
@@ -80,8 +84,15 @@ const AP_Param::GroupInfo AP_BattMonitor_INA2XX::var_info[] = {
     // @Range: 1 400
     // @Units: A
     // @User: Advanced
-    // @RebootRequired: True
     AP_GROUPINFO("MAX_AMPS", 27, AP_BattMonitor_INA2XX, max_amps, DEFAULT_BATTMON_INA2XX_MAX_AMPS),
+
+    // @Param: SHUNT
+    // @DisplayName: Battery monitor shunt resistor
+    // @Description: This sets the shunt resistor used in the device
+    // @Range: 0.0001 to 0.01
+    // @Units: Ohm
+    // @User: Advanced
+    AP_GROUPINFO("SHUNT", 28, AP_BattMonitor_INA2XX, rShunt, DEFAULT_BATTMON_INA2XX_SHUNT),
     
     AP_GROUPEND
 };
@@ -114,7 +125,6 @@ bool AP_BattMonitor_INA2XX::configure(DevType dtype)
     case DevType::INA226: {
         // configure for MAX_AMPS
         const uint16_t conf = (0x2<<9) | (0x5<<6) | (0x5<<3) | 0x7; // 2ms conv time, 16x sampling
-        const float rShunt = 0.0005;
         current_LSB = max_amps / 32768.0;
         voltage_LSB = 0.00125; // 1.25mV/bit
         const uint16_t cal = uint16_t(0.00512 / (current_LSB * rShunt));
@@ -130,7 +140,6 @@ bool AP_BattMonitor_INA2XX::configure(DevType dtype)
     case DevType::INA228: {
         // configure for MAX_AMPS
         voltage_LSB = 195.3125e-6; // 195.3125 uV/LSB
-        const float rShunt = 0.0005;
         current_LSB = max_amps / (1<<19);
         const uint16_t shunt_cal = uint16_t(13107.2e6 * current_LSB * rShunt) & 0x7FFF;
         if (write_word(REG_228_CONFIG, REG_228_CONFIG_RESET) && // reset
@@ -145,7 +154,6 @@ bool AP_BattMonitor_INA2XX::configure(DevType dtype)
     case DevType::INA238: {
         // configure for MAX_AMPS
         voltage_LSB = 3.125e-3; // 3.125mV/LSB
-        const float rShunt = 0.0005;
         current_LSB = max_amps / (1<<15);
         const uint16_t shunt_cal = uint16_t(819.2e6 * current_LSB * rShunt) & 0x7FFF;
         if (write_word(REG_238_CONFIG, REG_238_CONFIG_RESET) && // reset
diff --git a/libraries/AP_BattMonitor/AP_BattMonitor_INA2xx.h b/libraries/AP_BattMonitor/AP_BattMonitor_INA2xx.h
index 3175388b40..d49e7c8274 100644
--- a/libraries/AP_BattMonitor/AP_BattMonitor_INA2xx.h
+++ b/libraries/AP_BattMonitor/AP_BattMonitor_INA2xx.h
@@ -52,6 +52,7 @@ private:
     AP_Int8 i2c_bus;
     AP_Int8 i2c_address;
     AP_Float max_amps;
+    AP_Float rShunt;
     uint32_t failed_reads;
 
     struct {