Re[2]: [PHP] Confused about handling bytes
Hi,
Monday, May 21, 2007, 3:57:56 PM, you wrote:
TR Hi,
TR Monday, May 21, 2007, 10:50:27 AM, you wrote:
JV While I'm sure this is a stupid question and the solution will be
JV obvious to everyone here, this is confusing me.
JV I'm trying to control a device over a serial port using a PHP script,
JV and one of the things I need to do is read a 26-byte string from an
JV EEPROM, using a command that returns two bytes at a time, and write
JV similar strings using a similar command. For example, to read the first
JV two bytes of one such string beginning at address 0x484, I would send:
JV 04 84 00 00 BB
JV Here's the code I've written so far:
JV $string = 1; //which of 200 strings I want to read
JV $base = pack(H*,dechex((($string-1)*hexdec(0x1a))+hexdec(0x484)));
JV //calculate the base address of the string (the first starts at 0x484)
JV for($i=0;$i 13;$i++) { //iterate 13 times (26 bytes / 2 bytes at a time)
JV dio_write($serial,$base.\x00\x00\xbb,5); //send the command
JV $output[] = dio_read($serial,1); // read first byte
JV $output[] = dio_read($serial,1); // read second byte
JV $base = pack(H*,dechex(hexdec(bin2hex($base))+2)); //increment address
JV }
JV There are two things wrong with this. First, the final line isn't doing
JV what it's supposed to. Instead of adding 2 to the value of $base each
JV time, It's producing a pattern like this:
JV 0x484, 0x486, 0x73, 0x73, 0x73, 0x488, 0x48a, 0x48c, 0x48e, 0x490, 0x74,
JV 0x74, 0x74
JV Second, the format of $base doesn't seem to be handled correctly in line
JV 4 of the above code. Given a value of 0x484, this line should write the
JV bytes 04 84, but it is obviously not doing so, given the response I
JV get from the device (it sends FF FF instead of the expected value at
JV that address, which I get when I remove the variable and manually
JV specify the address).
JV What are the solutions to these problems?
JV Thanks,
JV -Joe Veldhuis
TR Do your packing after all the calculations:
TR ?php
TR $output = array();
TR $string = 1;
TR for(
TR $i=0, $base = (($string-1) * 26) + 0x484;
TR $i 26;
TR $i++, $base += 2)
TR {
TR $binarydata = pack(nc*, $base, 0, 0, 0xBB);
TR dio_write($serial,$k=strlen($binarydata),5); //send the command
TR $output[] = dio_read($serial,1); // read first byte
TR $output[] = dio_read($serial,1); // read second byte
TR }
TR --
TR regards,
TR Tom
I left some sebug in there, that should have been:
?php
$output = array();
$string = 1;
for(
$i=0, $base = (($string-1) * 26) + 0x484;
$i 26;
$i++, $base += 2)
{
$binarydata = pack(nc*, $base, 0, 0, 0xBB);
dio_write($serial,$binarydata,5); //send the command
$output[] = dio_read($serial,1); // read first byte
$output[] = dio_read($serial,1); // read second byte
}
--
regards,
Tom
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[PHP] Confused about handling bytes
While I'm sure this is a stupid question and the solution will be
obvious to everyone here, this is confusing me.
I'm trying to control a device over a serial port using a PHP script,
and one of the things I need to do is read a 26-byte string from an
EEPROM, using a command that returns two bytes at a time, and write
similar strings using a similar command. For example, to read the first
two bytes of one such string beginning at address 0x484, I would send:
04 84 00 00 BB
Here's the code I've written so far:
$string = 1; //which of 200 strings I want to read
$base = pack(H*,dechex((($string-1)*hexdec(0x1a))+hexdec(0x484)));
//calculate the base address of the string (the first starts at 0x484)
for($i=0;$i 13;$i++) { //iterate 13 times (26 bytes / 2 bytes at a time)
dio_write($serial,$base.\x00\x00\xbb,5); //send the command
$output[] = dio_read($serial,1); // read first byte
$output[] = dio_read($serial,1); // read second byte
$base = pack(H*,dechex(hexdec(bin2hex($base))+2)); //increment address
}
There are two things wrong with this. First, the final line isn't doing
what it's supposed to. Instead of adding 2 to the value of $base each
time, It's producing a pattern like this:
0x484, 0x486, 0x73, 0x73, 0x73, 0x488, 0x48a, 0x48c, 0x48e, 0x490, 0x74,
0x74, 0x74
Second, the format of $base doesn't seem to be handled correctly in line
4 of the above code. Given a value of 0x484, this line should write the
bytes 04 84, but it is obviously not doing so, given the response I
get from the device (it sends FF FF instead of the expected value at
that address, which I get when I remove the variable and manually
specify the address).
What are the solutions to these problems?
Thanks,
-Joe Veldhuis
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Re: [PHP] Confused about handling bytes
Hi,
Monday, May 21, 2007, 10:50:27 AM, you wrote:
JV While I'm sure this is a stupid question and the solution will be
JV obvious to everyone here, this is confusing me.
JV I'm trying to control a device over a serial port using a PHP script,
JV and one of the things I need to do is read a 26-byte string from an
JV EEPROM, using a command that returns two bytes at a time, and write
JV similar strings using a similar command. For example, to read the first
JV two bytes of one such string beginning at address 0x484, I would send:
JV 04 84 00 00 BB
JV Here's the code I've written so far:
JV $string = 1; //which of 200 strings I want to read
JV $base = pack(H*,dechex((($string-1)*hexdec(0x1a))+hexdec(0x484)));
JV //calculate the base address of the string (the first starts at 0x484)
JV for($i=0;$i 13;$i++) { //iterate 13 times (26 bytes / 2 bytes at a time)
JV dio_write($serial,$base.\x00\x00\xbb,5); //send the command
JV $output[] = dio_read($serial,1); // read first byte
JV $output[] = dio_read($serial,1); // read second byte
JV $base = pack(H*,dechex(hexdec(bin2hex($base))+2)); //increment address
JV }
JV There are two things wrong with this. First, the final line isn't doing
JV what it's supposed to. Instead of adding 2 to the value of $base each
JV time, It's producing a pattern like this:
JV 0x484, 0x486, 0x73, 0x73, 0x73, 0x488, 0x48a, 0x48c, 0x48e, 0x490, 0x74,
JV 0x74, 0x74
JV Second, the format of $base doesn't seem to be handled correctly in line
JV 4 of the above code. Given a value of 0x484, this line should write the
JV bytes 04 84, but it is obviously not doing so, given the response I
JV get from the device (it sends FF FF instead of the expected value at
JV that address, which I get when I remove the variable and manually
JV specify the address).
JV What are the solutions to these problems?
JV Thanks,
JV -Joe Veldhuis
Do your packing after all the calculations:
?php
$output = array();
$string = 1;
for(
$i=0, $base = (($string-1) * 26) + 0x484;
$i 26;
$i++, $base += 2)
{
$binarydata = pack(nc*, $base, 0, 0, 0xBB);
dio_write($serial,$k=strlen($binarydata),5); //send the command
$output[] = dio_read($serial,1); // read first byte
$output[] = dio_read($serial,1); // read second byte
}
--
regards,
Tom
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