Testing and reverse engineering a cheap Arduino Nano Expansion board, also pondering why GVS instead of GSV or GVSG.
Another impulse buy: Nano Multifunction Expansion Board for S$1.30 from an aliexpress seller.
Features of the board:
- 5.5 x 2.1mm barrel jack for power supply (recommended input voltage for Nano: 7-12V)
- additional red LED 5V power indicator
- additional AMS1117 3.3V regulator
- tantalum and ceramic input and output smoothing caps
- bank of 3 pairs of 3.3V + GND pins
- “GVS” (ground - voltage - signal) pin banks for each GPIO of the Nano
Sketching the schematic for the additional components that make up the expansion board:
Testing the board with a Nano installed:
An Aside on GVS
GVS is an unofficial standard for positioning ground and power with each signal pin:
- 0.1” pitch pins
- Ordered: Ground - Voltage - Signal
There are a large number of modules for input or output (e.g. sensors) that have a GVS connector. There is a 4 wire version (GVSS) for bidirectional serial communications.
I guess the original thinking was to keep the power wires together, and then add 1 or more signals to the end.
However on an expansion board like this it does mean a bit of a missed opportunity:
- if the order was GSV, then 2-pin jumpers could be used to pull the signal pin high or low
- with GVS, a 2-pin jumper can only be used to pull the signal high.
Perhaps a better design for an expansion board would be to put headers for GVSG:
- the GVS part could be used for standard GVS cable connections
- and the VSG part could be used to pull signal high or low with a 2-pin jumper