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For designs that must interface with existing hardware with precise timings, using any kind of microcontroller bitbanging often becomes unfeasible. Linus Akesso
by phire 5y ago
For designs that must interface with existing hardware with precise timings, using any kind of microcontroller bitbanging often becomes unfeasible. Linus Akesson's bit-banger and craft[1] only work because they drive all the the timings, and VGA is really permissive with timings.
And once you are past cheap Atmel or ARM micro-controllers, FPGA designs are often the most cost-effective.
This FPGA comes in at a unit cost of just $5.12 and allows a design of just the FPGA, the SRAM and a few level shifters.
Any design around a CPLD and/or raw 74 series logic would end up with a much higher BOM, and you would struggle to implement the scan-doubler functionality for 31khz output at a reasonable price point.
[1] Seriously impressive, check it out: https://www.linusakesson.net/scene/craft/index.php https://www.linusakesson.net/scene/craft/index.php
- phaedrus 5y agoThe Parallax Propeller is one microcontroller that could (in theory) work for bitbanging precise timings even when something else controls the timing. Since each task can be put on a dedicated core, you could clock-count your assembly instructions to sync up with the right time windows, and offload any variable-time tasks to a different routine on another core. The only caveat is access to the central memory store inside the microcontroller is round-robin (80MHz / 8 cores), so if the timing requirement was close to that limit (1/10MHz), you might have to do some gymnastics to make sure your routine grabs the right distribution of cores to get auspicious timing, and possibly reset and try again if that can't be achieved.