Fix for a certain TM1637 LED display

There are a miriad of low cost displays for hobbyists in online shops, particularly targeting Arduinos where libraries exist to drive the most common chips.

This article looks at a 4 digit LED module particularly suited to a digital clock display. The driver chip is a TM1637, and it requires Vcc and Gnd, a data IO wire and data clock wire.

Above is an example that just didn't work.

Above, scoping the data wires, it becomes clear that the rise and decay times are quite unsuited to the pulse rate. It may be possible to slow the pulse rate down and get it to work… but let's look for the root cause.

It turns out that there are 0.1µF caps from the DIO and CLK lines to ground, a huge capacitance given the speed at which the chip can work. The board above has had the caps removed, they were on the pads in the yellow box. If you see a listing with these caps, it might be worth skipping unless you are able to remove the caps.

Above, after removal of the caps, the pulse waveforms look much better… and the display now works.

Zooming in shows the rise times of the pulses to be hundreds of times faster with the caps removed