HMS NETWORKS CANbridge NT Lua ADK Bridge Router User Guide

Limiaons of the Ixxat Lua ADK  

CAN@net NT/CANbridge NT Lua ADK  

2.3. Limiaons of the Ixxat Lua ADK  

The Ixxat Lua ADK has hardware resource limiaons because code is loaded from the Flash le system into  

o-chip RAM and executed there. This RAM area is shared between Lua and other tasks on the target. The overall  

size is approximately 900 Kbyte. Therefore, Lua can use up to approximately 600 Kbyte RAM for code and data.  

The total amount of memory in use by Lua (in Kbytes) can be determined and wrien to the terminal window of  

the CAN-Gateway Conguraor with the following command:  

print(collectgarbage("count"))  

Keep in mind:  

• Lua scripts need much more CPU me than compiled code wrien in C.  

• Do as less as possible compuaon in Lua.  

• Do the compuaon with the lowest possible frequency.  

To reduce the eor for Lua:  

• If possible use mapping tables and other features.  

• Use the max_frequencyfeature for registered can messages to reduce the on_cancall frequency.  

• Use the array.repackuncon to reassemble CAN message payload.  

The needed CPU power can be monitored via the output in the status bar of the CAN-Gateway Conguraor. The  

Lua uncon sys.get_us_time()allows to measure execuon mes more precisely.  

A typical value for the execuon me of a short Lua uncon is 150 to 200 μs. About 5000–8000 messages can be  

processed per second.  

2.4. Specifcs in Coding for the Ixxat Lua ADK  

2.4.1. Bit Model 32 Bit Version  

The Ixxat Lua ADK is compiled for the 32 bit model. Therefore integer and oang points values are stored as 32  

bit values instead of 64 bit values as with a standard desktop Lua insallaon.  

2.4.2. Errors and Debugging  

The Ixxat CAN@net/CANbridge NT runs the Lua ADK over the nave hardware. There is an underlying kernel  

system to capture errors and to provide graceful failure modes. To avoid aecng the standard rmware, error  

handling is kept simple. If an error occurs when calling a Lua uncon, an error message is wrien to the log le  

and Lua is stopped. Runme errors in Lua uncons are wrien to the terminal and Lua is stopped. The rest of  

the rmware is running without resricons. To reacvae the Lua script the system has to be restarted.  

There is currently no target debugging support. The print statement diagnoscs through the terminal interface of  

the system must be used. The Ixxat Lua ADK provides a remote debugging feature to run the Lua script on the PC  

while communicang with the target device via an USB connecon.  

2.4.3. Declaring Variables  

Two types of data can be assigned to Lua variables:  

• values such as numbers, booleans, and strings  

• references such as uncons, tables, and user data  

For example, if the contents of variable aare assigned to variable b, there is a dierence between values and  

references. In case of a value, the content of ais copied into b. In case of a reference, both aand bnow refer to  

the same object. No content is copied. The Ixxat Lua ADK provides the uncon table.copy()which returns a  

deep copy of the provided table parameters.  

4.02.0332.20002 Version 1.5  

Page 3 of 20  

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