From 14089d491920d5b132154b17bdafdbf6019b7f2a Mon Sep 17 00:00:00 2001
From: Peter Barker <pbarker@barker.dropbear.id.au>
Date: Tue, 21 Feb 2023 20:35:57 +1100
Subject: [PATCH] AP_CANManager: add and use a "bool read(c)" method to AP_HAL

this is much less likely to not work vs the int16_t equivalent
---
 libraries/AP_CANManager/AP_SLCANIface.cpp | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/libraries/AP_CANManager/AP_SLCANIface.cpp b/libraries/AP_CANManager/AP_SLCANIface.cpp
index 62ccd0e44e..0656cece98 100644
--- a/libraries/AP_CANManager/AP_SLCANIface.cpp
+++ b/libraries/AP_CANManager/AP_SLCANIface.cpp
@@ -721,11 +721,11 @@ int16_t SLCAN::CANIface::receive(AP_HAL::CANFrame& out_frame, uint64_t& rx_time,
         uint32_t num_bytes = _port->available_locked(_serial_lock_key);
         // flush bytes from port
         while (num_bytes--) {
-            int16_t ret = _port->read_locked(_serial_lock_key);
-            if (ret < 0) {
+            uint8_t b;
+            if (!_port->read_locked(_serial_lock_key, b)) {
                 break;
             }
-            addByte(ret);
+            addByte(b);
             if (!rx_queue_.space()) {
                 break;
             }