SAM-III Construction Manual
See last page for document and copyright information, File: SAM-III Magnetometer Construction.doc, Page 24
Connect the null modem cable (supplied) between the SAM-III controller DB-9M connector and the
serial COM port on the computer. Note: The null modem cable uses only pins 2, 3 and 5 on the DB-9F
connectors, and the conductors for pins 2 and 3 are reversed on one of the connectors
A USB-serial interface adapter is required if your PC does not have a built-in serial port. If you use an
adapter, do not go any further in this document until you download and install the latest USB-serial
device drivers for your operating system. This is especially important with Windows 7. Upgrade your
drivers NOW.
In order to use the PIC loader program supplied with the SAM-III kit, the USB adapter must support
COM1, COM2, COM3, COM4, COM5 or COM6. The drivers supplied with most USB adapters allow the
COM Port to be set in this range. It may be necessary to use Advanced settings in Windows Device
Manager (Port Settings tab) to set the port within this range. If you change the port settings, be sure to
“bounce” (unplug and the re-plug) the USB-serial adapter for the new settings to take effect. For
additional information on USB port management:
http://www.reeve.com/Documents/Articles%20Papers/USBPortManagement_Reeve.pdf
DO NOT proceed until you have verified that you have the latest drivers for your USB-Serial Adapter.
This is especially important if you are using Windows 7. Check for the latest drivers now.
Initial Power Up
Connect the ac power adapter to the SAM-III controller board and plug the ac adapter into an ac outlet
receptacle. The LCD probably will not show anything at this time. With no sensor connected, the current
draw will be around 50 mA with the LCD backlight on and around 30 mA with it off. If the keyboard LED
is on, it will add about 10 mA load. Each sensor will add around 15 mA; however, at this time the sensors
should not be connected.
As already mentioned, the test firmware (IB3_ENG.HEX) is preinstalled. With that firmware and power
applied to the PCB, the LED on the keyboard will flash at ~2 Hz rate.
Adjust the LCD Contrast
The LCD contrast is adjusted by 21-turn potentiometer P3 (see illustration below). Slowly adjust P3 until
the display letters turn dark. Considerable adjustment may be needed. Continue turning slowly until the
display background just changes (background pixels start to show) and then back-off the adjustment just
enough so the background disappears. This setting provides good contrast for the present lighting
conditions. It may be necessary to readjust the contrast when you move the SAM-III to a new location.
If you have problems obtaining a display, proceed as follows: Measure the contrast voltage on the
center (slider) of potentiometer P3 (pin 3 on the LCD connector, pins 5-6 on the schematic). You should
be able to adjust the voltage from 0 to 5 V with P3. Voltage measurements on a lab system with good
contrast on the display showed 0.9 V. When it was adjusted to 1.5 V, the display disappeared. You can
save some trouble by turning the P3 adjustment screw at least 21
turns to the full counter-clockwise
(CCW) position. It does not have a mechanical stop but you will hear a faint click when it reaches the full
CCW position. Now, slowly adjust clockwise (CW) to adjust the display contrast. The lab systems
required adjusting 3-4 turns CW from the full counter-CCW position.
The display should now read:
