Ol' Blue Mod 1

After a short period of experimentation (running Ol' Blue around on the kitchen floor), it was quickly determined that the whisker bump sensors on the original version of Ol' Blue were far too fragile and tempermental. Consequently, my first "formal" design change, Ol' Blue Mod 1, was created. The whiskers were replaced by rubber tubing and momentary switches. The switches were from a COSMAC ELF II computer kit I built back in 1976. The age of these switches helped to maintain the vintage nature of Ol' Blue Mod 1.

At the time that the bump switches were changed, it was also decided to change the addressing scheme for the drive motor and turret motor controls. Originally, the control for the drive motors and the control for the turret motor were accessed through address 0x18 (write only) on the G-bus). This resulted in unnecessarily complicated bit masking to isolate changes in motor settings. The circuit change kept the drive motor control on G-bus address 0x18 (write only), but moved the turret motor control to G-bus address 0x19 (write only). In both cases, the addressing is write-only. These changes are illustrated in the GIO Interface Phase 4 control circuit.

Additional Photos

The left side of Ol' Blue Mod 1.
The front bumper of Ol' Blue Mod 1. The key numbers (0 and 1) also reflect the bit position of that switch in the sensor data when they are read.
The rear bumper of Ol' Blue Mod 1. The key numbers (2 and 3) also reflect the bit position of that switch in the sensor data when they are read.

Last updated Friday, March 9, 2007