From c28802c3d8bf5c6b570901a1a24433c280725940 Mon Sep 17 00:00:00 2001
From: Alex Janka <alex@alexjanka.com>
Date: Thu, 9 Jan 2025 11:32:02 +1100
Subject: [PATCH] ccs: tristar: get scaling on launch

this should also make Tristar::new return an error if the port exists
but doesn't have a modbus device there - previously this would fail
later when it times out reading registers
---
 charge-controller-supervisor/src/tristar.rs | 24 ++++++++++++---------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/charge-controller-supervisor/src/tristar.rs b/charge-controller-supervisor/src/tristar.rs
index 5cdf5d1..149ca19 100644
--- a/charge-controller-supervisor/src/tristar.rs
+++ b/charge-controller-supervisor/src/tristar.rs
@@ -52,7 +52,7 @@ pub struct Tristar {
     modbus: tokio_modbus::client::Context,
     charge_state_gauges: ChargeStateGauges,
     consecutive_errors: usize,
-    scaling: Option<Scaling>,
+    scaling: Scaling,
 }
 
 #[derive(Debug, Clone, Copy)]
@@ -261,7 +261,7 @@ impl Tristar {
     ) -> eyre::Result<Self> {
         let slave = tokio_modbus::Slave(DEVICE_ID);
 
-        let modbus = match transport {
+        let mut modbus = match transport {
             crate::config::Transport::Serial { port, baud_rate } => {
                 let modbus_serial = tokio_serial::SerialStream::open(
                     &tokio_serial::new(port, *baud_rate).timeout(std::time::Duration::from_secs(3)),
@@ -274,6 +274,13 @@ impl Tristar {
             }
         };
 
+        let scaling = {
+            let scaling_data = modbus
+                .read_holding_registers(0x0000, RAM_DATA_SIZE + 1)
+                .await??;
+            Scaling::from(&scaling_data)
+        };
+
         let charge_state_gauges = ChargeStateGauges::new(friendly_name);
 
         Ok(Self {
@@ -281,14 +288,14 @@ impl Tristar {
             modbus,
             charge_state_gauges,
             consecutive_errors: 0,
-            scaling: None,
+            scaling,
         })
     }
 
     pub async fn refresh(&mut self) -> eyre::Result<crate::controller::CommonData> {
         let new_state = self.get_data().await?;
 
-        self.scaling = Some(new_state.scaling);
+        self.scaling = new_state.scaling;
         self.consecutive_errors = 0;
         BATTERY_VOLTAGE
             .with_label_values(&[&self.friendly_name])
@@ -343,7 +350,7 @@ impl Tristar {
     }
 
     pub async fn set_target_voltage(&mut self, target_voltage: f64) -> eyre::Result<()> {
-        let scaled_voltage: u16 = self.scale_voltage(target_voltage)?;
+        let scaled_voltage: u16 = self.scale_voltage(target_voltage);
         self.modbus
             .write_single_register(TristarRamAddress::VbRefSlave as u16, scaled_voltage)
             .await??;
@@ -356,11 +363,8 @@ impl Tristar {
         Ok(())
     }
 
-    fn scale_voltage(&self, voltage: f64) -> eyre::Result<u16> {
-        let Some(scaling) = &self.scaling else {
-            return Err(eyre::eyre!("no scaling data present"));
-        };
-        Ok(scaling.inverse_voltage(voltage))
+    fn scale_voltage(&self, voltage: f64) -> u16 {
+        self.scaling.inverse_voltage(voltage)
     }
 
     async fn get_data(&mut self) -> eyre::Result<TristarState> {