Silicon Labs CP2101 based USB to UART adapter on Mac OS X

I bought some embedded controllers and a USB to TTL-level UART serial converter from Omnima web store. After some googling with the the USB vendor and product id I figured out that the converter was based on Silicon Labs CP2101 chip. I installed Mac OS X drivers from https://www.silabs.com/products/interface/usbtouart/Pages/default.aspx but no luck. The device wouldn't be recognised.

System profiler tells me the product id is 0x10c5 and vendor id 0x10ab (product 4293, vendor 4267 in decimal) but there was no entry for that combination in driver's plist - /System/Library/Extensions/SiLabsUSBDriver.kext/Contents/Info.plist.

The trick was to copypaste and modify one of the sections used to register the driver for product+vendor combinations. Just use the decimal form of product and vendor codes. Rebuild of driver cache had to be triggered by touching /System/Library/Extensions.

http://ciz.fi/~jkj/silab-mac-usb-driver.patch

After patching info.plist and rebuilding driver cache, plugging the device generated a device node in /dev/cu.SLAB_USBtoUART

Using pkgsrc in Mac OS X

Mac OS X has the default of case insensitive HFS+ file system and it seems to me that although case sensitive HFSX+ is supported, the OS is not heavily tested on it. E.g. FileVault won't work with it at all. I opted to case sensitive disk images.

Create and populate /usr/pkgsrc

# mkdir /Library/Images
# hdiutil create -volname pkgsrc -size 10g -type SPARSEBUNDLE -fs HFSX /Library/Images/pkgsrc
# mkdir /usr/pkgsrc
# hdiutil attach /Library/Images/pkgsrc.sparsebundle -nobrowse -mountpoint /usr/pkgsrc -owners on
# cd /usr
# cvs -z3 -d anoncvs@anoncvs.NetBSD.org:/cvsroot co -P pkgsrc
# cd /usr/pkgsrc
# cvs -d:pserver:anonymous@pkgsrc-wip.cvs.sourceforge.net:/cvsroot/pkgsrc-wip login
CVS password:
# cvs -z3 -d:pserver:anonymous@pkgsrc-wip.cvs.sourceforge.net:/cvsroot/pkgsrc-wip co -P wip

Create /usr/pkg

# hdiutil create -volname pkg -size 10g -type SPARSEBUNDLE -fs HFSX /Library/Images/pkg
# mkdir /usr/pkg
# hdiutil attach /Library/Images/pkg.sparsebundle -nobrowse -mountpoint /usr/pkg -owners on

Jvvm figured out how to mount the images at boot time. http://julipedia.blogspot.com/2007/04/mounting-volumes-on-mac-os-xs-startup.html. I made a few changes. There is a configuration file for mounting images:

/etc/hditab:
# HD Image Tab configuration file
# Imagefile options (for hdiutil attach)
/Library/Images/pkgsrc.sparsebundle -nobrowse -mountpoint /usr/pkgsrc -owners on
/Library/Images/pkg.sparsebundle -nobrowse -mountpoint /usr/pkg -owners on

Using jvvm's example I made a startup item directory /Library/StartupItems/DiskImages/ with the following files in it. The latter needs to be executable.

/Library/StartupItems/DiskImages/StartupParameters.plist:
{
Description = "Automatic attachment of disk images";
OrderPreference = "First";
Uses = ("Disks");
}

/Library/StartupItems/DiskImages/DiskImages:
#! /bin/sh
. /etc/rc.common

basePath="/Library/StartupItems/DiskImages"
tabFile="/etc/hditab"

doCompact() {
cat $tabFile | while read image rest ; do
image=${image%%#*}
[ -z "$image" ] && continue
hdiutil compact $image
done
}

StartService() {
doCompact
cat $tabFile | while read line ; do
line=${line%%#*}
[ -z "$line" ] && continue
hdiutil attach $line
done
}


StopService() {
true
}

RestartService() {
true
}

RunService "$1"

The images should be automatically mounted at boot. Test the script by umounting /usr/pkgsrc and /usr/pkg manually and running:
# /Library/StartupItems/DiskImages/DiskImages start

Next pkgsrc needs to be bootstrapped

# cd /usr/pkgsrc/bootstrap
# ./bootstrap --prefix /usr/pkg --pkgdbdir /usr/pkg/pkgdb --sysconfdir /usr/pkg/etc --varbase /usr/pkg/var

To add pkgsrc in your path create file /etc/path.d/pkgsrc with lines /usr/pkg/bin and /usr/pkg/sbin. Manual page search path is set in file /etc/manpath.d/pkgsrc with line /usr/pkg/man. There is a default mk.conf in /usr/pkg/etc/mk.conf. I made the following changes to mine.

/usr/pkg/etc/mk.conf:
COPTS?= -pipe ${DEFCOPTS}
CFLAGS+= -pipe

.ifdef BSD_PKG_MK # begin pkgsrc settings

PKG_DBDIR= /usr/pkg/pkgdb
LOCALBASE= /usr/pkg
VARBASE= /usr/pkg/var
PKG_TOOLS_BIN= /usr/pkg/sbin
PKGMANDIR= man

TOOLS_PLATFORM.pax?= /usr/pkg/bin/pax
TOOLS_PLATFORM.tar?= /usr/pkg/bin/tar

#MAKE_JOBS ?= 2
WRKOBJDIR ?= /usr/pkg/var/obj
MASTER_SORT ?= .fi .se .no .ee

PKG_DEFAULT_OPTIONS += inet6

_ACCEPTABLES=yes

.endif # end pkgsrc settings


I used sparse images here, because I'm short on disk space but there are cons; Sparse images cause disk fragmentation and removing files from the image doesn't free the space until the image is compacted. If you really want to tune it up make ~1GB DMG for /usr/pkgsrc, big sparce image for /usr/pkg and a ~2GB /usr/pkg/var DMG for changing data. The set WRKOBJDIR?=/usr/pkg/var/obj and DISTDIR?=/usr/pkg/var/distfiles in mk.conf.

Comments and hints are very welcome :)