PIC/C18 Compiler Tips and Troubleshooting - Revision history

Hwang: /* Erratic Behavior at End of Program */

2007-10-11T20:24:27Z

Erratic Behavior at End of Program

← Older revision		Revision as of 15:24, 11 October 2007
Line 27:		Line 27:
	===Erratic Behavior at End of Program===		===Erratic Behavior at End of Program===
	If you have a program where the PIC runs through the program once and stops and does nothing until it is reset, place a <tt>while(1){}</tt> loop at the end of the program to make the PIC enter a trap state.		If you have a program where the PIC runs through the program once and stops and does nothing until it is reset, place a <tt>while(1){}</tt> loop at the end of the program to make the PIC enter a trap state.

			===Changes to EEPROM Have No Effect===
			Try powering down and re-starting the PIC.

	==Tips==		==Tips==

Hwang: /* Erratic behavior at end of program */

2007-09-14T19:36:48Z

Erratic behavior at end of program

← Older revision		Revision as of 14:36, 14 September 2007
Line 25:		Line 25:
	You should also beware that baud rates are usually not exact. The system's clock generally has to be an integer multiple of the baud rate, so if a device has a 1 MHz clock, it is likely to use a baud rate of 111,111.111 bps (1,000,000/9) instead of the standard 115,200 bps. Although these systems can generally tolerate small differences in the baud rate, the possibility of mismatched baud rates contributing to errors should be kept in mind.		You should also beware that baud rates are usually not exact. The system's clock generally has to be an integer multiple of the baud rate, so if a device has a 1 MHz clock, it is likely to use a baud rate of 111,111.111 bps (1,000,000/9) instead of the standard 115,200 bps. Although these systems can generally tolerate small differences in the baud rate, the possibility of mismatched baud rates contributing to errors should be kept in mind.

	===Erratic ~~behavior~~ at ~~end~~ of ~~program~~===		===Erratic Behavior at End of Program===
	If you have a program where the PIC runs through the program once and stops and does nothing until it is reset, place a <tt>while(1){}</tt> loop at the end of the program to make the PIC enter a trap state.		If you have a program where the PIC runs through the program once and stops and does nothing until it is reset, place a <tt>while(1){}</tt> loop at the end of the program to make the PIC enter a trap state.

Hwang: /* Data corruption/erratic behavior */

2007-09-14T19:36:34Z

Data corruption/erratic behavior

← Older revision		Revision as of 14:36, 14 September 2007
Line 17:		Line 17:
	Note that printing floating point types with <tt>printf</tt> is not supported.		Note that printing floating point types with <tt>printf</tt> is not supported.

	===Data ~~corruption~~/~~erratic~~ ~~behavior~~===		===Data Corruption/Erratic Behavior===
	Beware if you have large arrays as local variables; you run the risk of a stack overflow. Try making large arrays global variables or '''static''' variables.		Beware if you have large arrays as local variables; you run the risk of a stack overflow. Try making large arrays global variables or '''static''' variables.

Hwang: /* Data Corruption/Erratic behavior */

2007-09-14T19:36:18Z

Data Corruption/Erratic behavior

← Older revision		Revision as of 14:36, 14 September 2007
Line 17:		Line 17:
	Note that printing floating point types with <tt>printf</tt> is not supported.		Note that printing floating point types with <tt>printf</tt> is not supported.

	===Data ~~Corruption~~/~~Erratic~~ behavior===		===Data corruption/erratic behavior===
	Beware if you have large arrays as local variables; you run the risk of a stack overflow. Try making large arrays global variables or '''static''' variables.		Beware if you have large arrays as local variables; you run the risk of a stack overflow. Try making large arrays global variables or '''static''' variables.

Hwang: /* Erratic Behavior at End of Program */

2007-09-14T19:36:00Z

Erratic Behavior at End of Program

← Older revision		Revision as of 14:36, 14 September 2007
Line 25:		Line 25:
	You should also beware that baud rates are usually not exact. The system's clock generally has to be an integer multiple of the baud rate, so if a device has a 1 MHz clock, it is likely to use a baud rate of 111,111.111 bps (1,000,000/9) instead of the standard 115,200 bps. Although these systems can generally tolerate small differences in the baud rate, the possibility of mismatched baud rates contributing to errors should be kept in mind.		You should also beware that baud rates are usually not exact. The system's clock generally has to be an integer multiple of the baud rate, so if a device has a 1 MHz clock, it is likely to use a baud rate of 111,111.111 bps (1,000,000/9) instead of the standard 115,200 bps. Although these systems can generally tolerate small differences in the baud rate, the possibility of mismatched baud rates contributing to errors should be kept in mind.

	===Erratic ~~Behavior~~ at ~~End~~ of ~~Program~~===		===Erratic behavior at end of program===
	If you have a program where the PIC runs through the program once and stops and does nothing until it is reset, place a <tt>while(1){}</tt> loop at the end of the program to make the PIC enter a trap state.		If you have a program where the PIC runs through the program once and stops and does nothing until it is reset, place a <tt>while(1){}</tt> loop at the end of the program to make the PIC enter a trap state.

Hwang: /* Troubleshooting */

2007-09-14T19:35:32Z

Troubleshooting

← Older revision		Revision as of 14:35, 14 September 2007
Line 16:		Line 16:
	===printf===		===printf===
	Note that printing floating point types with <tt>printf</tt> is not supported.		Note that printing floating point types with <tt>printf</tt> is not supported.

			===Data Corruption/Erratic behavior===
			Beware if you have large arrays as local variables; you run the risk of a stack overflow. Try making large arrays global variables or '''static''' variables.

	===Serial Communications Data Corruption===		===Serial Communications Data Corruption===
Line 21:		Line 24:

	You should also beware that baud rates are usually not exact. The system's clock generally has to be an integer multiple of the baud rate, so if a device has a 1 MHz clock, it is likely to use a baud rate of 111,111.111 bps (1,000,000/9) instead of the standard 115,200 bps. Although these systems can generally tolerate small differences in the baud rate, the possibility of mismatched baud rates contributing to errors should be kept in mind.		You should also beware that baud rates are usually not exact. The system's clock generally has to be an integer multiple of the baud rate, so if a device has a 1 MHz clock, it is likely to use a baud rate of 111,111.111 bps (1,000,000/9) instead of the standard 115,200 bps. Although these systems can generally tolerate small differences in the baud rate, the possibility of mismatched baud rates contributing to errors should be kept in mind.

			===Erratic Behavior at End of Program===
			If you have a program where the PIC runs through the program once and stops and does nothing until it is reset, place a <tt>while(1){}</tt> loop at the end of the program to make the PIC enter a trap state.

	==Tips==		==Tips==

Hwang: /* Using Arithmetic */

2007-09-10T23:09:10Z

Using Arithmetic

← Older revision		Revision as of 18:09, 10 September 2007
Line 51:		Line 51:

	====Using Arithmetic====		====Using Arithmetic====
	Another way of doing this is to use arithmetic. For a 16-bit integer, the most significant byte can be obtained by dividing the value by 256. The least significant byte can be obtained by using the modulus function with 256.		Another way of doing this is to use arithmetic. For a 16-bit integer, the most significant byte can be obtained by dividing the value by 256. The least significant byte can be obtained by using the modulus function with 256.
	Example:		Example:
	<pre>		<pre>
Line 71:		Line 71:
	byte2 = 0xAB;		byte2 = 0xAB;
	byte1 = 0xCD;		byte1 = 0xCD;
	someInteger = (int)byte2*256 + byte1;		someInteger = (unsigned int)byte2*256 + (unsigned int)byte1;
	</pre>		</pre>

			Beware that this isn't going to give you the correct result if you leave <tt>byte1</tt> and <tt>byte2</tt> as signed chars, because signed chars could be negative. Therefore, we place the <tt>(unsigned int)</tt> keywords to cast them as unsigned integers before performing the operations.

Hwang: /* Using Arithmetic */

2007-09-10T22:52:33Z

Using Arithmetic

@@ Line 61: / Line 61: @@
 byte2 = someInteger/256;
 byte1 = someInteger%256;
 </pre>

Hwang: /* Using Unions */

2007-09-10T22:40:39Z

Using Unions

← Older revision		Revision as of 17:40, 10 September 2007
Line 26:		Line 26:
	There are some situations where you may need to split a multi-byte variable into its component bytes (for example, writing to 16-bit registers or sending data through the serial port).		There are some situations where you may need to split a multi-byte variable into its component bytes (for example, writing to 16-bit registers or sending data through the serial port).
	====Using Unions====		====Using Unions====
	One way to do this is to use the '''<tt>union</tt>''' data type. A <tt>union</tt> is like a <tt>struct</tt>, except all the members share the same location in memory. Therefore, if have a union with one <tt>int</tt> variable and an array of two <tt>char</tt> variables, writing to the <tt>int</tt> variable will automatically fill in the <tt>char</tt> as well, and vice versa.		One way to do this is to use the '''<tt>union</tt>''' data type. A <tt>union</tt> is like a <tt>struct</tt>, except all the members share the same location in memory. Therefore, if have a union with one <tt>int</tt> variable and an array of two <tt>char</tt> variables, writing to the <tt>int</tt> variable will automatically fill in the <tt>char</tt> fields as well, and vice versa.

	Example:		Example:

Hwang: /* printf */

2007-09-10T22:40:08Z

printf

← Older revision		Revision as of 17:40, 10 September 2007
Line 16:		Line 16:
	===printf===		===printf===
	Note that printing floating point types with <tt>printf</tt> is not supported.		Note that printing floating point types with <tt>printf</tt> is not supported.

			===Serial Communications Data Corruption===
			If you are having trouble with RS-232 communications with other devices, remember that the RS-232 standard uses -8V to -15V for a low signal and 8V to 15V for a high signal, whereas the PIC uses 0V and 5V, respectively. If you are interfacing the PIC with a standard RS-232 device, such as the serial port on a PC, you will need a voltage shifting chip such as the [[media:ST232_datasheet.pdf\|ST232 RS-232 Voltage Shifter]].

			You should also beware that baud rates are usually not exact. The system's clock generally has to be an integer multiple of the baud rate, so if a device has a 1 MHz clock, it is likely to use a baud rate of 111,111.111 bps (1,000,000/9) instead of the standard 115,200 bps. Although these systems can generally tolerate small differences in the baud rate, the possibility of mismatched baud rates contributing to errors should be kept in mind.

	==Tips==		==Tips==