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Syscalls are OS functions exposed by Ndless to C and assembly programs. This article describes the syscalls currently available with Ndless 4.2 r2004.

Your help is needed to make this list grow to a full-fledged library. Try to find new syscalls, test them and share them for integration in Ndless.

C standard library and some POSIX functions

All standard C functions and some POSIX functions (like dirent.h) are available via newlib, except:

  • int link(const char *oldpath, const char *newpath)
  • int fstat(int fd, struct stat *buf)
  • int kill(pid_t pid, int sig)
  • int ftruncate(int fd, off_t length) and int truncate(const char *path, off_t length) (Not implemented yet,


  • int TCT_Local_Control_Interrupts(int mask): sets the interrupt mask. Returns the previous mask.
  • int NU_Current_Dir(const char *drive, char *path): fills in path with the full path name of the current working directory. Use "A:" as drive. Returns 0 on success.
  • int NU_Get_First(struct dstat *statobj, const char * pattern): given a pattern which contains both a path specifier and a search pattern, fills in the structure at statobj with information about the file and sets up internal parts of statobj to supply appropriate information for calls to NU_Get_Next. Returns non-zero if a match was not found.
  • int NU_Get_Next(struct dstat *statobj): given a pointer to a DSTAT structure that has been set up by a call to NU_Get_First(), searches for the next match of the original pattern in the original path. Returns non-zero if found and updates statobj for subsequent calls to NU_Get_Next.
  • void NU_Done(struct dstat *statobj): given a pointer to a DSTAT structure that has been set up by a call to NU_Get_First(), frees internal elements used by the statobj.
  • void NU_Set_Current_Dir(const char *name): Set the current working directory on the default drive.

TI-Nspire Lua extensions

Ndless can expose C functions to the TI-Nspire Lua engine through Ndless Lua Extensions. Most functions of the Lua C API are available.

This is an experimental feature. Ndless v3.6 or higher is recommended.

The luaext example of the Ndless SDK is a good start to write your own Ndless Lua extension.

  1. Write a Ndless program that uses the Lua C API to register Lua object and exits immediately
  2. Build the Lua extension to a binary file named [extension_name].luax.tns and drop it (and ask the users to drop it) to any folder of the calculator
  3. Write a TI-Nspire Lua script. It should load the Lua extension with the following statement:
    nrequire [extension_name]
  4. Use from the Lua script any Lua object registered by the Lua extension
    Note : on Ndless 3.1, the 'require' keyword was used, which starting from OS v3.6 isn't available anymore.
  5. Run the Lua script. The 'nrequire' statement will fail if Ndless hasn't been installed on the calculator. An error will be displayed if the Lua extension isn't found.
  6. Enjoy the TI-Nspire Lua API and OS integration powered by native functions

TI-Nspire specific

UTF-16 String API

Since v3.1 r672.

  • String : The type of the dynamic-length strings encoded in utf-16 format
 typedef struct {
   char * str;
   int len;
   int chunk_size;
   int unknown_field;
 } * String;
Init/Dispose functions
  • String string_new() : Returns a new String structure
  • void string_free(String) : Frees the String structure
Encoding functions
  • char * string_to_ascii(String) : Returns String converted to ascii
  • int string_set_ascii(String, char *) : Erases the content of the String with the given ascii string
  • int string_set_utf16(String, char *) : Erases the content of the String with the given utf16 string
String manipulation functions
  • void string_lower(String) : Lower all characters in the String
  • int string_concat_utf16(String, char *) : Concatenates to the String the given utf16 string
  • void string_erase(String, int n) : Erases characters in the String from beginning to n (equivalent to substring(n, len))
  • void string_truncate(String, int n) : Truncates the String to n chararacters (equivalent to substring(0, n))
  • int string_insert_replace_utf16(String, char *, int start, int end) : Inserts the given utf16 string between start and end in the String by erasing its content. If end is -1 it erases the end of the String
  • int string_insert_utf16(String, char *, int pos) : Inserts the given utf16 string at pos in the String.
  • int string_sprintf_utf16(String, char *, ...) : Fills the String using the utf16 string format and arguments (equivalent to sprintf but with utf16 everywhere)
Search functions
  • char string_charAt(String, int pos) : Returns the character at pos in the String
  • int string_indexOf_utf16(String, int start, char *pattern) : Returns the index of pattern in the String starting at start. Returns -1 if not found
  • int string_last_indexOf_utf16(String, int start, char *) : Returns the last index of pattern in the String starting at start. Returns -1 if not found
  • int string_compareTo_utf16(String, char *) : Returns 0 if the given utf16 string is equal to the String, -1 if it is superior, 1 if not
  • char * string_substring_utf16(String, char *pattern, int *ptr) : Returns the beginning of the String (in utf16) until pattern is met (excluded). ptr is modified so that it indicates the ending index of pattern or values -1 if the pattern doesn't exist. In such case the whole string is returned.
  • char * string_substring(String dst, String src, int start, int end) : Writes in the dst the resulting substring from start to end (excluded) of src. Also returns the utf16 pointer
Other UTF-16 functions
  • void ascii2utf16(void *buf, const char *str, int max_size): converts the UTF-8 string str to the UTF-16 string buf of size max_size.
  • void utf162ascii(void *buf, const char *str, int max_size): Since v3.1 r607. converts the UTF-16 string str to the UTF-8 string buf of size max_size.
  • size_t utf16_strlen(const char * s): Since v3.1 r607. Returns the length in characters (including the finalizing null) of the UTF-16 string s.


Graphic Context API

Since v3.1 r903.

The TI-Nspire Graphic Context (or "ngc") is an API created by TI, inspired by Java's Graphics2D and using Nucleus GRAFIX functions.

This API is intensively used by the OS internally and is directly exposed in the TI-Nspire Lua framework.

In order to use this API inside your program, use this line:

#include <ngc.h>

The Ndless SDK provides an GC-based demo in ndless-sdk/samples/ngc/.

Global parameters
  • Gc *gui_gc_global_GC_ptr is the graphic context used (and already allocated/setup) by the OS. In fact, gui_gc_new has been removed from the syscall list because it made the TI-Nspire Clickpad/Touchpad crash, preferring the use of this graphic context. Furthermore, the OS seems to use the same gc from the beginning of its initialization, why not Ndless then?.

Notice: It is recommended to save the value of gui_gc_global_GC_ptr in a local variable as such:

Gc gc = *gui_gc_global_GC_ptr;

The gc is an off-screen buffer. Thus, each function that draws on this gc will not affect the screen until you use gui_gc_blit_to_screen(gc).

The OS tends to blit the screen if it has been updated using a timed Nucleus task. You can use this principle in your programs but nothing forces you to do so. Thus, you can freely blit the screen as many times as you want when running an animation and only refresh part of it using gui_gc_blit_to_screen_region(gc, x, y, w, h) when needed.

Init/Dispose functions
  • Gc gui_gc_copy(Gc, int w, int h) - Allocates a new Gc from an existing one copying its parameters, replacing port's width & height with the given ones. Does not copy the screen buffer.
  • int gui_gc_begin(Gc) - Initializes graphic port (seems to allocate 2 memory areas), may be used before any graphic manipulation.

Notice: gui_gc_setRegion may be used before gui_gc_begin in order to make gui_gc_clipRect work with proper coordinates.

  • void gui_gc_finish(Gc) - Resets the graphic port parameters (seems to free 2 memory areas).
  • void gui_gc_free(Gc) - Frees the given gc.
Set/Get Attributes functions
  • void gui_gc_clipRect(Gc, int x, int y, int w, int h, gui_gc_ClipRectOp op) - Contrains the given gc to draw only in a certain area. If op is GC_CRO_RESET, the other parameters are ignored.
  • void gui_gc_setColorRGB(Gc, int r, int g, int b) - Changes the pen color of the given gc
  • void gui_gc_setColor(Gc, int color) - same as gui_gc_setColorRGB but using 0xRRGGBB color format
  • void gui_gc_setAlpha(Gc, gui_gc_Alpha) - Changes the pen alpha mode of the given gc to non-transparent or semi-transparent.
  • void gui_gc_setFont(Gc, gui_gc_Font) - Changes the font of the given gc
  • gui_gc_Font gui_gc_getFont(Gc) - Returns the current font of the given gc
  • void gui_gc_setPen(Gc, gui_gc_PenSize, gui_gc_PenMode) - Changes the pen size and mode of the given gc
  • void gui_gc_setRegion(Gc, int xs, int ys, int ws, int hs, int x, int y, int w, int h) - Changes the region (or viewport) of the given gc. The region <x,y,w,h> is based on screen coordinates <xs,ys,ws,hs>. gui_gc_setRegion will offset all the drawings and coordinates you are using: It can be useful to use this function instead of creating a separate gc to draw an inner window.

Notice: gui_gc_clipRect will work with old coordinates as long as you don't reset the region to the entire screen, for example, by using this main:

int main(void)
  /* Get the gc */
  Gc gc = *gui_gc_global_GC_ptr;

  /* Initialization */

  /* Draw */
  gui_gc_clipRect(gc, 10, 10, 10, 10, GC_CRO_SET);
  gui_gc_fillRect(gc, 0, 0, SCREEN_WIDTH, SCREEN_HEIGHT); /* Will only draw a 10x10 rectangle */

  /* Blit & finish */

  return 0;
Draw functions
  • void gui_gc_fillArc(Gc, int x, int y, int w, int h, int start, int end) - Fills an arc inside the box <x,y,w,h>. start and end have to be multiplied by 10.
/* Disk at <0,0> of size <20,20> */
gui_gc_fillArc(gc, 0, 0, 20, 20, 0, 3600);
  • void gui_gc_fillPoly(Gc, int * points, int count) - Fills a polygon shape. points is a table of successive x,y coordinates.
/* Filled rectangle shape at <100,100> of size <50,50> */
int points[] = {100,100, 150,100, 150,150, 100,150, 100,100};
gui_gc_fillPoly(gc, points, sizeof (points) / sizeof (points[0]));
  • void gui_gc_fillRect(Gc, int x, int y, int w, int h) - Fills a rectangle.
/* Filled rectangle at <100,100> of size <50,50> */
gui_gc_fillRect(gc, 100, 100, 50, 50);
  • void gui_gc_fillGradient(Gc, int x, int y1, int w, int y2, int start_color, int end_color, int vertical) - Fills a line-based gradient from start_color to end_color (both in 0xRRGGBB format). As a side-effect, current color is changed to end_color after the call. May only work for certain color pairs (it may be cleverer to recreate this function rectangle-based by your own).
/* Black to White vertical gradient at <10,10> of size <50,50> */
gui_gc_fillGradient(gc, 10, 10, 50, 50, 0x000000, 0xffffff, 1);
  • void gui_gc_drawArc(Gc, int x, int y, int w, int h, int start, int end) - Draws an arc insidethe box <x,y,w,h>. start and end have to be multiplied by 10.
/* Circle at <0,0> of size <20,20> */
gui_gc_drawArc(gc, 0, 0, 20, 20, 0, 3600);
  • void gui_gc_drawLine(Gc, int x1, int y1, int x2, int y2) - Draws a line from <x1,y1> to <x2,y2>.
/* Line from <0,0> to <320,240> */
gui_gc_drawLine(gc, 0, 0, 320, 240);
  • void gui_gc_drawRect(Gc, int x, int y, int w, int h) - Draws an empty rectangle at <x,y> of size <w,h>
/* Empty rectangle at <100,100> of size <50,50> */
gui_gc_fillRect(gc, 100, 100, 50, 50);
  • void gui_gc_drawString(Gc, char * utf16, int x, int y, gui_gc_StringMode flags) - Draws an UTF-16 Null-terminated string at <x,y> using flags.
/* "Hello" where <50,50> is actually the top left of it */
gui_gc_drawString(gc, "H\0e\0l\0l\0o\0\0", 50, 50, GC_SM_TOP);
/* Upside-down "World" at <100,100> */
gui_gc_drawString(gc, "W\0o\0r\0l\0d\0\0", 100, 100, GC_SM_DOWN);
  • void gui_gc_drawPoly(Gc, int * points, int count) - Draws a polygon shape. points is a table of successive x,y coordinates.
/* Empty rectangle shape at <100,100> of size <50,50> */
int points[] = {100,100, 150,100, 150,150, 100,150, 100,100};
gui_gc_fillPoly(gc, points, sizeof (points) / sizeof (points[0]));
  • void gui_gc_drawIcon(Gc, int res, int icon, int x, int y) - Draws an icon pre-defined by the OS.
/* Draw a star at <100,100> */
gui_gc_drawIcon(gc, RES_SYST, 255, 100, 100);
  • void gui_gc_drawSprite(Gc, gui_gc_Sprite *, int x, int y) - Draws a sprite at <x,y>. Sprite pixels color is affected by gui_gc_setColor[RGB]
/* Draw a hand-made gradient at <100, 100> */
gui_gc_Sprite s = {.width = 9, .height = 1};
s.pixels = (char *) {0x0, 0x22, 0x44, 0x66, 0x88, 0xAA, 0xCC, 0xEE, 0xFF};
gui_gc_drawSprite(gc, &s, 100, 100);
  • void gui_gc_drawImage(Gc, char * TI_Image, int x, int y) - Draws an image in TI.Image format at <x,y>
/* Gray image at <100,100> of size <10,10> */
gui_gc_Image_header hdr = {.width = 10, .height = 10, .empty = 0, .depth = 2, .enc = 1};
hdr.buff_size = hdr.depth * hdr.width;
unsigned size = hdr.buff_size * hdr.height;
char * img = calloc(size + sizeof (gui_gc_Image_header), 1);
memcpy(img, &hdr, sizeof (gui_gc_Image_header));
memset(img + sizeof (gui_gc_Image_header), 77, size);
gui_gc_drawImage(gc, img, 100, 100);
Metric functions
  • int gui_gc_getStringWidth(Gc, gui_gc_Font, char * utf16, int start, int length) -
  • int gui_gc_getCharWidth(Gc, gui_gc_Font, short utf16 char) -
  • int gui_gc_getStringSmallHeight(Gc, gui_gc_Font, char * utf16, int start, int length) -
  • int gui_gc_getCharHeight(Gc, gui_gc_Font, short utf16 char) -
  • int gui_gc_getStringHeight(Gc, gui_gc_Font, char * utf16, int start, int length) -
  • int gui_gc_getFontHeight(Gc, gui_gc_Font) -
  • int gui_gc_getIconSize(Gc, int ressource, int icon, int * w, int * h) -
Blit functions
  • void gui_gc_blit_to_screen(Gc gc) - Blits the screen using the given gc
  • void gui_gc_blit_to_screen_region(Gc gc, int x, int y, int w, int h) - Blits part of the screen (region <x,y,w,h>) using the given gc
  • void gui_gc_blit_gc(Gc source, int xs, int ys, int ws, int hs, Gc dest, int xd, int yd, int wd, int hd) - Blits (and Stretch with a cubic interpolation if <wd,hd> is different than <wd,hd>) from rectangle <xs,ys,ws,hs> of source to rectangle <xd,yd,wd,hd> of dest.

Notice: On OS 3.1 CX/CM, when stretching only, there is a bug that distorts the source rectangle depending on the destination ratio. Even the OS shows this bug, for example Ctrl+N, 2, Ctrl+Up will not center the axes whereas on OS 3.2 it will.

  • void gui_gc_blit_buffer(Gc gc, char * buffer, int xb, int yb, int wb, int hb) - Blits a rectangle <xb,yb,wb,hb> from buffer to the given gc. Strangely, buffer has to be 320 pixels wide in order to have the correct offsets. Also, buffer has to be allocated according to the platform: On Clickpads/Touchpads use 1/2bpp (thus, 160xH), on CM/CX use 2bpp (thus 320x2xH).

Notice: In order to be compatible with Clickpads/Touchpads (1/2 bpp vs 2bpp), x has to be a the same parity of the current Region's x

unsigned size = 320 * 15 * 2;
if (!lcd_isincolor()) size >>= 2;

char * buff = malloc(size);
memset(buff, 0x44, size);

/* Draws a green rectangle at <11,20> of size <15,15> */
gui_gc_setRegion(gc, 11, 20, 15, 15, 0, 0, 15, 15);
gui_gc_blit_buffer(gc, buff, 1, 0, 15, 15);


You may notice the spare space unused. Thus, this method is only recommended to be use on fullscreen buffers. For example, this method is used by the internal 3D engine of the OS.


NavNet is the TI-Nspire specific USB Protocol and API for calc-to-calc and computer-to-calc transfers. It allows bidirectional and multi-service exposition with connections initiated from the calculator or the computer, abstracting the host/device orientation of USB. The protocol takes care of acknowledgement, and supports network of calculators built with the TI-Nspire™ Navigator System. Standard services such as file transfer or directory listing are available, and custom services can be implemented.

Request and response messages contain arbitrary data of at most 254 bytes. The convention for the standard services is:

  • a single command byte at the beginning of the request packet, with optional parameters data
  • a single acknowledgement byte at the beginning of the request packet, with optional response data, or a 2 byte error code

NavNet does not help with the construction of request and response data.

Starting from v3.1 r893 Ndless and the Ndless SDK support a subset of the NavNet API. Windows (with Computer Link or Student Software) is required on the computer side, but a Linux/Mac OS X version based on the TiLP libraries may be available in the future. Bidirectional calc-to-calc transfers don't appear to fully work yet as there seems to be limitations in NavNet that make one or the two calculator reboot in some conditions.

The NdlessEditor of the Ndless SDK also shows an example of computer-to-calc file transfer supporting the Tools > Transfer the program to calc menu. The source code is available in cmd_tools/navnet_cmd. A startup script is used on the computer side that puts navnet.dll onto the PATH.

The NavNet API

The functions are directly available for the TI-Nspire. For computer connection, the navnet.h and libnavnet.a library (wrapper for the navnet.dll library) in ndless_pc/ of the Ndless SDK must be used.

All functions return a number >= 0 in case of success that should be checked.

  • int16_t TI_NN_Init(const char *opts): (computer side) starts the NavNet stack with parameters opts. You'll typically use -c 1 -d 0, where the -c and -d switches are the log level respectively for the console and the NavNet debug file. Note that the stack cannot be started if Student Software is already running, and transfers without initialization may interfer with transfers from Student Software.
  • int16_t TI_NN_Shutdown(void): (computer side) stops the NavNet stack.
  • int16_t TI_NN_RegisterNotifyCallback(uint32_t filter_flags, void (*cb)(void)): (computer side, broken on calculator side) register for connection events. A connection event is published even if a device was plugged in before the NavNet stack initialization. filter_flags should be zero. The parameters passed to the callback function are currently unknown. The computer program should wait for a notification after a TT_Init() and before a node enumeration, else the enumeration will fail.
  • nn_oh_t TI_NN_CreateOperationHandle(void): create an operation handle to be used with some NavNet functions.
  • int16_t TI_NN_DestroyOperationHandle(nn_oh_t oh): destroy an operation handle.
  • int16_t TI_NN_NodeEnumInit(nn_oh_t oh): initiates a node (computer or device) enumeration. Enumeration is required to find the partner computer or device.
  • int16_t TI_NN_NodeEnumNext(nn_oh_t oh, nn_nh_t *nh): writes the node handle of the next partner computer or device found to nh. The first node handle can be used when assuming a single node network.
  • int16_t TI_NN_NodeEnumDone(nn_oh_t oh): terminates a node enumeration.
  • int16_t TI_NN_Connect(nn_nh_t nh, uint32_t service_id, nn_ch_t *ch): connects to a remote service with service identifier service_id (see the list of standard identifiers, or use a custom service id for custom services). Note that this functions only set up the client node and doesn't transmit any packet.
  • int16_t TI_NN_Disconnect(nn_ch_t ch): disconnects from a remote service by sending a disconnection packet.
  • int16_t TI_NN_Write(nn_ch_t ch, void *buf, uint32_t data_size): writes a packet to a remote service. The payload is data_size long and pointed to by buf.
  • int16_t TI_NN_Read(nn_ch_t ch, uint32_t timeout_ms, void *buf, uint32_t buf_size, uint32_t *recv_size): waits until a packet is received or a timeout. The size of the packet received is written to recv_size. Data is written to buf of buf_size bytes long. A packet size can be at most TI_NN_GetConnMaxPktSize().
  • uint32_t TI_NN_GetConnMaxPktSize(nn_ch_t ch): returns the maximum packet size for request and response.
  • int16_t TI_NN_StartService(uint32_t service_id, void *data, void (*cb)(nn_ch_t ch, void *data)): exposes a service. data will be passed as the data parameter of the callback function, and may be NULL. The service identifier musn't conflict with standard identifiers.
  • int16_t TI_NN_StopService(uint32_t service_id): stops exposing a service.
  • int16_t TI_NN_PutFile(nn_nh_t nh, nn_oh_t oh, const char *local_path, const char *remote_path): transfers a file from local_path to remote_path. The local path must be absolute. The remote path is relative to the /documents TI-Nspire folder. You must first TI_NN_Connect() to service 0x4060 before using it.

The following functions are not yet implemented:

  • TI_NN_UnregisterNotifyCallback
  • TI_NN_InstallOS
  • TI_NN_GetNodeInfo
  • TI_NN_GetNodeScreen
  • TI_NN_CopyFile
  • TI_NN_Rename
  • TI_NN_RmDir
  • TI_NN_MkDir
  • TI_NN_DeleteFile
  • TI_NN_GetFileAttributes
  • TI_NN_DirEnumDone
  • TI_NN_DirEnumNext
  • TI_NN_DirEnumInit
  • TI_NN_GetFile