I am researching the Bastille for a project in which I have to depict the Royal soldiers that stood on the towers during the French Revolution. Specifically, I am looking for the types of weapons present on the tower (esp. cannons or other type of artillery), as well as the firearms that the soldiers would have employed.
The Wikipedia entry on the Bastille says in its paragraph about the storming of the Bastille:
[...] an additional force of 32 soldiers from the Swiss Salis-Samade regiment had been assigned to the Bastille on 7 July, adding to the existing 82 invalides pensioners who formed the regular garrison [...] The Bastille was defended by 30 small artillery pieces [...] He [sc. Bernard-René de Launay, commander of the Bastille] was protecting a recently arrived stock of 250 barrels of valuable gunpowder [...]
French artillery was apparently standardized under the De Vallière system since the 1730s, so one can reasonably assume that "small artillery piece" would refer to a 4 pound or 8 pound (weight of the cannonball) gun.
Following Wikipedia further this is confirmed in the main article on the storming of the bastille:
The walls mounted eighteen eight-pound guns and twelve smaller pieces.
The fact that this is on Wikipedia might indicate that this is trivia by the standards of history SE.
Keep in mind that the Bastille was a fortress, and a large armory. The main weapons at the time were muskets, which the Bastille had plenty of in addition to tons of ammunition.