From 17b6530cf9462f1c71c156d02fc230a0c13b85fc Mon Sep 17 00:00:00 2001
From: Thomas Watson <twatson52@icloud.com>
Date: Thu, 27 Jun 2024 22:23:21 -0500
Subject: [PATCH 1/3] AP_Scripting: remove use of uint32_t_ud from serial
 bindings

Avoids the hassle of having to convert results to regular numbers in
scripts. We trust the user will not be processing 2GiB of data in one
call or attempting to go past 2 gigabaud.
---
 .../AP_Scripting/AP_Scripting_SerialAccess.cpp      | 13 ++++++++-----
 libraries/AP_Scripting/AP_Scripting_SerialAccess.h  |  4 ++--
 libraries/AP_Scripting/docs/docs.lua                |  6 +++---
 libraries/AP_Scripting/drivers/EFI_DLA.lua          |  4 ++--
 libraries/AP_Scripting/drivers/Generator_SVFFI.lua  |  2 +-
 .../AP_Scripting/drivers/Hobbywing_DataLink.lua     |  4 ++--
 libraries/AP_Scripting/drivers/INF_Inject.lua       |  2 +-
 libraries/AP_Scripting/examples/readstring_test.lua |  4 ++--
 .../generator/description/bindings.desc             |  6 +++---
 libraries/AP_Scripting/lua_bindings.cpp             |  1 +
 libraries/AP_Scripting/tests/serial_loopback.lua    |  2 +-
 11 files changed, 26 insertions(+), 22 deletions(-)

diff --git a/libraries/AP_Scripting/AP_Scripting_SerialAccess.cpp b/libraries/AP_Scripting/AP_Scripting_SerialAccess.cpp
index f82ef3a127e9ef..d58e101ca04ffa 100644
--- a/libraries/AP_Scripting/AP_Scripting_SerialAccess.cpp
+++ b/libraries/AP_Scripting/AP_Scripting_SerialAccess.cpp
@@ -24,9 +24,9 @@ void AP_Scripting_SerialAccess::begin(uint32_t baud)
     }
 }
 
-size_t AP_Scripting_SerialAccess::write(uint8_t c)
+int32_t AP_Scripting_SerialAccess::write(uint8_t c)
 {
-    return write(&c, 1);
+    return (int32_t)write(&c, 1); // return value will be 0 or 1
 }
 
 size_t AP_Scripting_SerialAccess::write(const uint8_t *buffer, size_t size)
@@ -54,12 +54,15 @@ ssize_t AP_Scripting_SerialAccess::read(uint8_t* buffer, uint16_t count)
     return ON_DEVICE_PORT(read, buffer, count);
 }
 
-uint32_t AP_Scripting_SerialAccess::available(void)
+int32_t AP_Scripting_SerialAccess::available(void)
 {
+    uint32_t avail;
     if (!check_is_device_port()) {
-        return stream->available();
+        avail = stream->available();
+    } else {
+        avail = ON_DEVICE_PORT(available);
     }
-    return ON_DEVICE_PORT(available);
+    return MIN(avail, (uint32_t)INT32_MAX); // ensure result fits in a Lua integer
 }
 
 void AP_Scripting_SerialAccess::set_flow_control(enum AP_HAL::UARTDriver::flow_control fcs)
diff --git a/libraries/AP_Scripting/AP_Scripting_SerialAccess.h b/libraries/AP_Scripting/AP_Scripting_SerialAccess.h
index 7231359c818552..13f377fc6804cf 100644
--- a/libraries/AP_Scripting/AP_Scripting_SerialAccess.h
+++ b/libraries/AP_Scripting/AP_Scripting_SerialAccess.h
@@ -14,13 +14,13 @@ class AP_Scripting_SerialAccess {
 
     void begin(uint32_t baud);
 
-    size_t write(uint8_t c);
+    int32_t write(uint8_t c);
     size_t write(const uint8_t *buffer, size_t size);
 
     int16_t read(void);
     ssize_t read(uint8_t *buffer, uint16_t count);
 
-    uint32_t available(void);
+    int32_t available(void);
 
     void set_flow_control(enum AP_HAL::UARTDriver::flow_control fcs);
 
diff --git a/libraries/AP_Scripting/docs/docs.lua b/libraries/AP_Scripting/docs/docs.lua
index b1c73afce10e45..0ac806a0b1cc2c 100644
--- a/libraries/AP_Scripting/docs/docs.lua
+++ b/libraries/AP_Scripting/docs/docs.lua
@@ -1234,12 +1234,12 @@ function AP_HAL__I2CDevice_ud:set_retries(retries) end
 local AP_Scripting_SerialAccess_ud = {}
 
 -- Start serial port with the given baud rate (no effect for device ports)
----@param baud_rate uint32_t_ud|integer|number
+---@param baud_rate integer
 function AP_Scripting_SerialAccess_ud:begin(baud_rate) end
 
 -- Writes a single byte
 ---@param value integer -- byte to write
----@return uint32_t_ud -- 1 if success else 0
+---@return integer -- 1 if success else 0
 function AP_Scripting_SerialAccess_ud:write(value) end
 
 -- Writes a string. The number of bytes actually written, i.e. the length of the
@@ -1260,7 +1260,7 @@ function AP_Scripting_SerialAccess_ud:read() end
 function AP_Scripting_SerialAccess_ud:readstring(count) end
 
 -- Returns number of available bytes to read.
----@return uint32_t_ud
+---@return integer
 function AP_Scripting_SerialAccess_ud:available() end
 
 -- Set flow control option for serial port (no effect for device ports)
diff --git a/libraries/AP_Scripting/drivers/EFI_DLA.lua b/libraries/AP_Scripting/drivers/EFI_DLA.lua
index 9c764ac4a38b2f..3e054df76069b7 100644
--- a/libraries/AP_Scripting/drivers/EFI_DLA.lua
+++ b/libraries/AP_Scripting/drivers/EFI_DLA.lua
@@ -88,7 +88,7 @@ state.total_fuel_cm3 = 0.0
    check for input and parse data
 --]]
 local function check_input()
-   local n_bytes = uart:available():toint()
+   local n_bytes = uart:available()
    --gcs:send_text(MAV_SEVERITY.INFO, string.format("n_bytes=%u %.2f", n_bytes, millis():tofloat()*0.001))
    if n_bytes < 82 then
       return
@@ -108,7 +108,7 @@ local function check_input()
    state.last_read_us = micros()
 
    -- discard the rest
-   discard_bytes(uart:available():toint())
+   discard_bytes(uart:available())
 end
 
 --[[
diff --git a/libraries/AP_Scripting/drivers/Generator_SVFFI.lua b/libraries/AP_Scripting/drivers/Generator_SVFFI.lua
index eae7678a253c41..459b9106ac610d 100644
--- a/libraries/AP_Scripting/drivers/Generator_SVFFI.lua
+++ b/libraries/AP_Scripting/drivers/Generator_SVFFI.lua
@@ -149,7 +149,7 @@ state.last_status = -1
    check for input and parse data
 --]]
 local function check_input()
-   local n_bytes = uart:available():toint()
+   local n_bytes = uart:available()
    --gcs:send_text(MAV_SEVERITY.INFO, string.format("n_bytes=%u %.2f", n_bytes, millis():tofloat()*0.001))
    if n_bytes < 31 then
       return
diff --git a/libraries/AP_Scripting/drivers/Hobbywing_DataLink.lua b/libraries/AP_Scripting/drivers/Hobbywing_DataLink.lua
index 76a490146a9eb5..95c2f83642a5c0 100644
--- a/libraries/AP_Scripting/drivers/Hobbywing_DataLink.lua
+++ b/libraries/AP_Scripting/drivers/Hobbywing_DataLink.lua
@@ -76,7 +76,7 @@ end
    discard pending bytes
 --]]
 local function discard_pending()
-   local n = uart:available():toint()
+   local n = uart:available()
    for _ = 1, n do
       uart:read()
    end
@@ -168,7 +168,7 @@ local telem_data = ESCTelemetryData()
    check for input and parse data
 --]]
 local function check_input()
-   local n_bytes = uart:available():toint()
+   local n_bytes = uart:available()
    if n_bytes < 160 then
       return
    end
diff --git a/libraries/AP_Scripting/drivers/INF_Inject.lua b/libraries/AP_Scripting/drivers/INF_Inject.lua
index d967439a9f4bff..f25cbfe6fd0fbc 100644
--- a/libraries/AP_Scripting/drivers/INF_Inject.lua
+++ b/libraries/AP_Scripting/drivers/INF_Inject.lua
@@ -168,7 +168,7 @@ end
 --]]
 local function check_input()
    local packet_size = 83
-   local n_bytes = uart:available():toint()
+   local n_bytes = uart:available()
    if n_bytes < packet_size then
       return false
    end
diff --git a/libraries/AP_Scripting/examples/readstring_test.lua b/libraries/AP_Scripting/examples/readstring_test.lua
index d95a0687be8e59..fa83db54a8b42c 100644
--- a/libraries/AP_Scripting/examples/readstring_test.lua
+++ b/libraries/AP_Scripting/examples/readstring_test.lua
@@ -32,14 +32,14 @@ end
 
 function update()
    -- test using 4.5 method
-   local n = port:available():toint()
+   local n = port:available()
    if n > 0 then
       local str = get_string_45(n)
       gcs:send_text(0, string.format("Received: '%s'", str))
    end
 
    -- test using 4.4 method (just so we don't have an unused function in lua check)
-   n = port:available():toint()
+   n = port:available()
    if n > 0 then
       local str = get_string_44(n)
       gcs:send_text(0, string.format("Received: '%s'", str))
diff --git a/libraries/AP_Scripting/generator/description/bindings.desc b/libraries/AP_Scripting/generator/description/bindings.desc
index 1c2deb44d80a8b..8c06ee34f25486 100644
--- a/libraries/AP_Scripting/generator/description/bindings.desc
+++ b/libraries/AP_Scripting/generator/description/bindings.desc
@@ -395,12 +395,12 @@ singleton RC_Channels method get_aux_cached boolean RC_Channel::AUX_FUNC'enum 0
 include AP_Scripting/AP_Scripting_SerialAccess.h
 -- don't let user create access objects
 userdata AP_Scripting_SerialAccess creation null -1
-userdata AP_Scripting_SerialAccess method begin void uint32_t 1U UINT32_MAX
-userdata AP_Scripting_SerialAccess method write uint32_t uint8_t'skip_check
+userdata AP_Scripting_SerialAccess method begin void int32_t 1 INT32_MAX
+userdata AP_Scripting_SerialAccess method write int32_t uint8_t'skip_check
 userdata AP_Scripting_SerialAccess manual writestring lua_serial_writestring 1 1
 userdata AP_Scripting_SerialAccess method read int16_t
 userdata AP_Scripting_SerialAccess manual readstring lua_serial_readstring 1 1
-userdata AP_Scripting_SerialAccess method available uint32_t
+userdata AP_Scripting_SerialAccess method available int32_t
 userdata AP_Scripting_SerialAccess method set_flow_control void AP_HAL::UARTDriver::flow_control'enum AP_HAL::UARTDriver::FLOW_CONTROL_DISABLE AP_HAL::UARTDriver::FLOW_CONTROL_RTS_DE
 
 -- serial is not a real C++ type here, but its name never gets used in C++ as we only have manual methods
diff --git a/libraries/AP_Scripting/lua_bindings.cpp b/libraries/AP_Scripting/lua_bindings.cpp
index 7b817821cda170..dddc0029cdfe9f 100644
--- a/libraries/AP_Scripting/lua_bindings.cpp
+++ b/libraries/AP_Scripting/lua_bindings.cpp
@@ -792,6 +792,7 @@ int lua_serial_writestring(lua_State *L)
     // get the bytes the user wants to write, along with their length
     size_t req_bytes;
     const char *data = lua_tolstring(L, 2, &req_bytes);
+    req_bytes = MIN(req_bytes, (size_t)INT32_MAX); // ensure result fits in a Lua integer
 
     // write up to that number of bytes
     const uint32_t written_bytes = port->write((const uint8_t*)data, req_bytes);
diff --git a/libraries/AP_Scripting/tests/serial_loopback.lua b/libraries/AP_Scripting/tests/serial_loopback.lua
index 9893c8f7d8e47f..5c39656a4c4bd0 100644
--- a/libraries/AP_Scripting/tests/serial_loopback.lua
+++ b/libraries/AP_Scripting/tests/serial_loopback.lua
@@ -11,7 +11,7 @@ function test_driver_to_device()
   local msg_send = "hello device"
   local num_sent = 0
   for ci = 1,#msg_send do
-    num_sent = num_sent + ser_driver:write(msg_send:byte(ci, ci)):toint()
+    num_sent = num_sent + ser_driver:write(msg_send:byte(ci, ci))
   end
   local msg_recv = ser_device:readstring(#msg_send)
   if msg_send == msg_recv and num_sent == #msg_send then

From 353099a93d3169d32b84391f5f1963343ab9b10c Mon Sep 17 00:00:00 2001
From: Thomas Watson <twatson52@icloud.com>
Date: Thu, 27 Jun 2024 22:35:06 -0500
Subject: [PATCH 2/3] AP_Scripting: replace -1 return from SerialAccess:read()
 with nil

Reduces likelihood of programming errors caused by forgetting to check
the return value.

Use a manual binding to ensure we return nil instead of nothing.
---
 .../AP_Scripting_SerialAccess.cpp             |  8 ++----
 .../AP_Scripting/AP_Scripting_SerialAccess.h  |  2 +-
 libraries/AP_Scripting/docs/docs.lua          |  2 +-
 libraries/AP_Scripting/drivers/EFI_DLA.lua    |  4 ++-
 .../AP_Scripting/drivers/Generator_SVFFI.lua  |  4 ++-
 .../drivers/Hobbywing_DataLink.lua            |  4 ++-
 libraries/AP_Scripting/drivers/INF_Inject.lua |  1 +
 .../AP_Scripting/examples/readstring_test.lua |  1 +
 .../generator/description/bindings.desc       |  2 +-
 libraries/AP_Scripting/lua_bindings.cpp       | 25 +++++++++++++++----
 libraries/AP_Scripting/lua_bindings.h         |  1 +
 11 files changed, 37 insertions(+), 17 deletions(-)

diff --git a/libraries/AP_Scripting/AP_Scripting_SerialAccess.cpp b/libraries/AP_Scripting/AP_Scripting_SerialAccess.cpp
index d58e101ca04ffa..678fc87022aca5 100644
--- a/libraries/AP_Scripting/AP_Scripting_SerialAccess.cpp
+++ b/libraries/AP_Scripting/AP_Scripting_SerialAccess.cpp
@@ -37,13 +37,9 @@ size_t AP_Scripting_SerialAccess::write(const uint8_t *buffer, size_t size)
     return ON_DEVICE_PORT(write, buffer, size);
 }
 
-int16_t AP_Scripting_SerialAccess::read(void)
+bool AP_Scripting_SerialAccess::read(uint8_t &c)
 {
-    uint8_t c;
-    if (read(&c, 1) != 1) {
-        return -1;
-    }
-    return c;
+    return read(&c, 1) > 0;
 }
 
 ssize_t AP_Scripting_SerialAccess::read(uint8_t* buffer, uint16_t count)
diff --git a/libraries/AP_Scripting/AP_Scripting_SerialAccess.h b/libraries/AP_Scripting/AP_Scripting_SerialAccess.h
index 13f377fc6804cf..de6c1d64073736 100644
--- a/libraries/AP_Scripting/AP_Scripting_SerialAccess.h
+++ b/libraries/AP_Scripting/AP_Scripting_SerialAccess.h
@@ -17,7 +17,7 @@ class AP_Scripting_SerialAccess {
     int32_t write(uint8_t c);
     size_t write(const uint8_t *buffer, size_t size);
 
-    int16_t read(void);
+    bool read(uint8_t &c);
     ssize_t read(uint8_t *buffer, uint16_t count);
 
     int32_t available(void);
diff --git a/libraries/AP_Scripting/docs/docs.lua b/libraries/AP_Scripting/docs/docs.lua
index 0ac806a0b1cc2c..ac4668ea7075fe 100644
--- a/libraries/AP_Scripting/docs/docs.lua
+++ b/libraries/AP_Scripting/docs/docs.lua
@@ -1250,7 +1250,7 @@ function AP_Scripting_SerialAccess_ud:write(value) end
 function AP_Scripting_SerialAccess_ud:writestring(data) end
 
 -- Reads a single byte from the serial port
----@return integer -- byte, -1 if error or none available
+---@return integer|nil -- byte, or nil on error/none available
 function AP_Scripting_SerialAccess_ud:read() end
 
 -- Reads up to `count` bytes and returns the bytes read as a string. No bytes
diff --git a/libraries/AP_Scripting/drivers/EFI_DLA.lua b/libraries/AP_Scripting/drivers/EFI_DLA.lua
index 3e054df76069b7..3a5c0bd8a437e8 100644
--- a/libraries/AP_Scripting/drivers/EFI_DLA.lua
+++ b/libraries/AP_Scripting/drivers/EFI_DLA.lua
@@ -75,7 +75,9 @@ end
 local function read_bytes(n)
    local ret = ""
    for _ = 1, n do
-      ret = ret .. string.char(uart:read())
+      local b = uart:read()
+      assert(b)
+      ret = ret .. string.char(b)
    end
    return ret
 end
diff --git a/libraries/AP_Scripting/drivers/Generator_SVFFI.lua b/libraries/AP_Scripting/drivers/Generator_SVFFI.lua
index 459b9106ac610d..04b3af2dce2ecc 100644
--- a/libraries/AP_Scripting/drivers/Generator_SVFFI.lua
+++ b/libraries/AP_Scripting/drivers/Generator_SVFFI.lua
@@ -69,7 +69,9 @@ end
 local function read_bytes(n)
    local ret = ""
    for _ = 1, n do
-      ret = ret .. string.char(uart:read())
+      local b = uart:read()
+      assert(b)
+      ret = ret .. string.char(b)
    end
    return ret
 end
diff --git a/libraries/AP_Scripting/drivers/Hobbywing_DataLink.lua b/libraries/AP_Scripting/drivers/Hobbywing_DataLink.lua
index 95c2f83642a5c0..e1a8330f907299 100644
--- a/libraries/AP_Scripting/drivers/Hobbywing_DataLink.lua
+++ b/libraries/AP_Scripting/drivers/Hobbywing_DataLink.lua
@@ -67,7 +67,9 @@ uart:begin(115200)
 local function read_bytes(n)
    local ret = ""
    for _ = 1, n do
-      ret = ret .. string.char(uart:read())
+      local b = uart:read()
+      assert(b)
+      ret = ret .. string.char(b)
    end
    return ret
 end
diff --git a/libraries/AP_Scripting/drivers/INF_Inject.lua b/libraries/AP_Scripting/drivers/INF_Inject.lua
index f25cbfe6fd0fbc..a4432f8ef714ca 100644
--- a/libraries/AP_Scripting/drivers/INF_Inject.lua
+++ b/libraries/AP_Scripting/drivers/INF_Inject.lua
@@ -140,6 +140,7 @@ local function read_bytes(n)
    local ret = ""
    for _ = 1, n do
       local b = uart:read()
+      assert(b)
       state.chk0 = state.chk0 ~ b
       state.chk1 = state.chk1 ~ state.chk0
       ret = ret .. string.char(b)
diff --git a/libraries/AP_Scripting/examples/readstring_test.lua b/libraries/AP_Scripting/examples/readstring_test.lua
index fa83db54a8b42c..5667c343d6c593 100644
--- a/libraries/AP_Scripting/examples/readstring_test.lua
+++ b/libraries/AP_Scripting/examples/readstring_test.lua
@@ -17,6 +17,7 @@ local function get_string_44(n)
    local ret = ""
    for _ = 1, n do
       local b = port:read()
+      assert(b)
       ret = ret .. string.char(b)
    end
    return ret
diff --git a/libraries/AP_Scripting/generator/description/bindings.desc b/libraries/AP_Scripting/generator/description/bindings.desc
index 8c06ee34f25486..4ea1147e51f3de 100644
--- a/libraries/AP_Scripting/generator/description/bindings.desc
+++ b/libraries/AP_Scripting/generator/description/bindings.desc
@@ -398,7 +398,7 @@ userdata AP_Scripting_SerialAccess creation null -1
 userdata AP_Scripting_SerialAccess method begin void int32_t 1 INT32_MAX
 userdata AP_Scripting_SerialAccess method write int32_t uint8_t'skip_check
 userdata AP_Scripting_SerialAccess manual writestring lua_serial_writestring 1 1
-userdata AP_Scripting_SerialAccess method read int16_t
+userdata AP_Scripting_SerialAccess manual read lua_serial_read 0 1
 userdata AP_Scripting_SerialAccess manual readstring lua_serial_readstring 1 1
 userdata AP_Scripting_SerialAccess method available int32_t
 userdata AP_Scripting_SerialAccess method set_flow_control void AP_HAL::UARTDriver::flow_control'enum AP_HAL::UARTDriver::FLOW_CONTROL_DISABLE AP_HAL::UARTDriver::FLOW_CONTROL_RTS_DE
diff --git a/libraries/AP_Scripting/lua_bindings.cpp b/libraries/AP_Scripting/lua_bindings.cpp
index dddc0029cdfe9f..b6ffb7916cb990 100644
--- a/libraries/AP_Scripting/lua_bindings.cpp
+++ b/libraries/AP_Scripting/lua_bindings.cpp
@@ -803,6 +803,21 @@ int lua_serial_writestring(lua_State *L)
     return 1;
 }
 
+int lua_serial_read(lua_State *L) {
+    binding_argcheck(L, 1);
+
+    AP_Scripting_SerialAccess * port = check_AP_Scripting_SerialAccess(L, 1);
+
+    uint8_t c;
+    if (port->read(c)) {
+        lua_pushinteger(L, c);
+    } else {
+        lua_pushnil(L); // error, return nil
+    }
+
+    return 1;
+}
+
 int lua_serial_readstring(lua_State *L) {
     binding_argcheck(L, 2);
 
@@ -815,13 +830,13 @@ int lua_serial_readstring(lua_State *L) {
 
     // read up to that number of bytes
     const ssize_t read_bytes = port->read(data, req_bytes);
-    if (read_bytes < 0) {
-        return 0; // error, return nil
+    if (read_bytes >= 0) {
+        // push the buffer as a string, truncated to the number of bytes actually read
+        luaL_pushresultsize(&b, read_bytes);
+    } else {
+        lua_pushnil(L); // error, return nil
     }
 
-    // push the buffer as a string, truncated to the number of bytes actually read
-    luaL_pushresultsize(&b, read_bytes);
-
     return 1;
 }
 
diff --git a/libraries/AP_Scripting/lua_bindings.h b/libraries/AP_Scripting/lua_bindings.h
index 53b5f4b5ae6563..28e882b3455d52 100644
--- a/libraries/AP_Scripting/lua_bindings.h
+++ b/libraries/AP_Scripting/lua_bindings.h
@@ -13,6 +13,7 @@ int lua_get_CAN_device2(lua_State *L);
 int lua_serial_find_serial(lua_State *L);
 int lua_serial_find_simulated_device(lua_State *L);
 int lua_serial_writestring(lua_State *L);
+int lua_serial_read(lua_State *L);
 int lua_serial_readstring(lua_State *L);
 int lua_dirlist(lua_State *L);
 int lua_removefile(lua_State *L);

From b9d7dc48cbea58950d11148cb05c8cde5d7f6800 Mon Sep 17 00:00:00 2001
From: Thomas Watson <twatson52@icloud.com>
Date: Sun, 30 Jun 2024 11:28:47 -0500
Subject: [PATCH 3/3] AP_Scripting: replace int return from
 SerialAccess:write() with bool

Avoids the pitfall of 0 being truthy in Lua. Now, `if port:write() then`
will work as expected.
---
 libraries/AP_Scripting/AP_Scripting_SerialAccess.cpp       | 4 ++--
 libraries/AP_Scripting/AP_Scripting_SerialAccess.h         | 2 +-
 libraries/AP_Scripting/docs/docs.lua                       | 2 +-
 libraries/AP_Scripting/generator/description/bindings.desc | 2 +-
 libraries/AP_Scripting/tests/serial_loopback.lua           | 2 +-
 5 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/libraries/AP_Scripting/AP_Scripting_SerialAccess.cpp b/libraries/AP_Scripting/AP_Scripting_SerialAccess.cpp
index 678fc87022aca5..d8a47f731fd9f4 100644
--- a/libraries/AP_Scripting/AP_Scripting_SerialAccess.cpp
+++ b/libraries/AP_Scripting/AP_Scripting_SerialAccess.cpp
@@ -24,9 +24,9 @@ void AP_Scripting_SerialAccess::begin(uint32_t baud)
     }
 }
 
-int32_t AP_Scripting_SerialAccess::write(uint8_t c)
+bool AP_Scripting_SerialAccess::write(uint8_t c)
 {
-    return (int32_t)write(&c, 1); // return value will be 0 or 1
+    return write(&c, 1) > 0;
 }
 
 size_t AP_Scripting_SerialAccess::write(const uint8_t *buffer, size_t size)
diff --git a/libraries/AP_Scripting/AP_Scripting_SerialAccess.h b/libraries/AP_Scripting/AP_Scripting_SerialAccess.h
index de6c1d64073736..c3dec6d18c72fa 100644
--- a/libraries/AP_Scripting/AP_Scripting_SerialAccess.h
+++ b/libraries/AP_Scripting/AP_Scripting_SerialAccess.h
@@ -14,7 +14,7 @@ class AP_Scripting_SerialAccess {
 
     void begin(uint32_t baud);
 
-    int32_t write(uint8_t c);
+    bool write(uint8_t c);
     size_t write(const uint8_t *buffer, size_t size);
 
     bool read(uint8_t &c);
diff --git a/libraries/AP_Scripting/docs/docs.lua b/libraries/AP_Scripting/docs/docs.lua
index ac4668ea7075fe..035919c5a9f3e4 100644
--- a/libraries/AP_Scripting/docs/docs.lua
+++ b/libraries/AP_Scripting/docs/docs.lua
@@ -1239,7 +1239,7 @@ function AP_Scripting_SerialAccess_ud:begin(baud_rate) end
 
 -- Writes a single byte
 ---@param value integer -- byte to write
----@return integer -- 1 if success else 0
+---@return boolean -- true if successfully written
 function AP_Scripting_SerialAccess_ud:write(value) end
 
 -- Writes a string. The number of bytes actually written, i.e. the length of the
diff --git a/libraries/AP_Scripting/generator/description/bindings.desc b/libraries/AP_Scripting/generator/description/bindings.desc
index 4ea1147e51f3de..85b5fdd50765a8 100644
--- a/libraries/AP_Scripting/generator/description/bindings.desc
+++ b/libraries/AP_Scripting/generator/description/bindings.desc
@@ -396,7 +396,7 @@ include AP_Scripting/AP_Scripting_SerialAccess.h
 -- don't let user create access objects
 userdata AP_Scripting_SerialAccess creation null -1
 userdata AP_Scripting_SerialAccess method begin void int32_t 1 INT32_MAX
-userdata AP_Scripting_SerialAccess method write int32_t uint8_t'skip_check
+userdata AP_Scripting_SerialAccess method write boolean uint8_t'skip_check
 userdata AP_Scripting_SerialAccess manual writestring lua_serial_writestring 1 1
 userdata AP_Scripting_SerialAccess manual read lua_serial_read 0 1
 userdata AP_Scripting_SerialAccess manual readstring lua_serial_readstring 1 1
diff --git a/libraries/AP_Scripting/tests/serial_loopback.lua b/libraries/AP_Scripting/tests/serial_loopback.lua
index 5c39656a4c4bd0..b84622b6fdba93 100644
--- a/libraries/AP_Scripting/tests/serial_loopback.lua
+++ b/libraries/AP_Scripting/tests/serial_loopback.lua
@@ -11,7 +11,7 @@ function test_driver_to_device()
   local msg_send = "hello device"
   local num_sent = 0
   for ci = 1,#msg_send do
-    num_sent = num_sent + ser_driver:write(msg_send:byte(ci, ci))
+    num_sent = num_sent + (ser_driver:write(msg_send:byte(ci, ci)) and 1 or 0)
   end
   local msg_recv = ser_device:readstring(#msg_send)
   if msg_send == msg_recv and num_sent == #msg_send then