Solved: How to use 'unsigned char' C data type with Win32::API

[sam_bakki]

Dear Perl Monks,

I need a help in Win32::API

I am working on a hardware test automation, The interface to hardware is USB-I2C and we have a C DLL which exports set of functions to communicate with hardware.

I am trying to import the C DLL via Win32::API module so i can automate some test cases via perl. Right now, I could able to read & write to particular memory address using the exported APIs in DLL

I have a problem with one API , Which is i2cGetDeviceAddress , it returns unsigned char. I could not able to properly use Win32::API to get the data from this API. This API is working well in C code

I have given API prototype in C , C code and its output and my perl code

Please help me to use 'unsigned char' with Win32::API module.

use Win32::API;

#C proptype
# typedef unsigned char __stdcall i2cGetDeviceAddress_type();
# extern i2cGetDeviceAddress_type *i2cGetDeviceAddress;


#C++ Prototype
# extern "C" Byte __stdcall i2cGetDeviceAddress(void);

# C Code
# printf ("\n \n DEV: %d , %c , %x ", i2cGetDeviceAddress(),i2cGetDevi
+ceAddress(),i2cGetDeviceAddress());
#
# Output: DEV: 70 , F , 46

#Perl Code

# When i use 'char' as a return type , API is not returning anything
# my $i2cGetDeviceAddressFunc = Win32::API->new('CrdI2C32', 'char i2cG
+etDeviceAddress()') or warn "\n ERROR: Can not import API:i2cGetDevic
+eAddress ,  $^E ,";

# When i use 'unsigned char' as a return type, I get, Win32::API::pars
+e_prototype: WARNING unknown output parameter type 'unsigned'
#my $i2cGetDeviceAddressFunc = Win32::API->new('CrdI2C32', 'unsigned c
+har i2cGetDeviceAddress()') or warn "\n ERROR: Can not import API:i2c
+GetDeviceAddress ,  $^E ,";

# So, I used INT , The following way is working for some other API but
+ not this API :(
my $i2cGetDeviceAddressFunc = Win32::API->new('CrdI2C32', 'INT i2cGetD
+eviceAddress()') or warn "\n ERROR: Can not import API:i2cGetDeviceAd
+dress ,  $^E ,";

my $ret = 0;

$ret = $i2cGetDeviceAddressFunc->Call();

$ret = unpack ('C*',pack ("i",$ret));

print "\n $ret "; # prints 152

$ret = sprintf ("0x%X",$ret); 

print "\n $ret"; #prints 0x98 but i wanted 0x46

Update:
OS: Windows 7 Perl: Active Perl 5.12 , x86 flavour (MSWin32-x86-multi-thread)

UPDATE: Problem is solved

The above code itself is fine. I was confused with API call sequence. When I call I2CWrite API and then i2cGetDeviceAddress , It is providing correct output (i.e 70)

Thanks a Lot to BrowserUk his suggestion was useful to me to implement some other API using Win32::API

Thanks to tye for the $ret &= 0xFF; tip. I did not know this, That is why i am using complex pack & unpack