I am trying to interface with the TMS9918ANL (TI's Video Display Processor, 30 years old!). Min voltage requires for this chip is 4.75V.
I use the ATMEGA to control it, and supply the system with a 5V supply via my PC's USB port. Everything is on breadboard. I have two pieces of breadboards connected together, where each chip resides on each. When I measure the voltage at the GND and Vcc pins of the TMS9918ANL, I only get around 3.5V. Why the voltage drop there? In fact, measuring the voltage on the breadboard that gets connected to the USB power, I get around 4.85V. But measuring the voltage of the other breadboard, I get around 3.5-3.7V. I should be getting consistently 4.8-4.9V across the breadboards.
Thanks for any tips.