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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