When the PNP's Emitter is at +12V, you cannot turn it off by presenting +5V to its Base - because 5V is still less positive than Emitter potential (in fact, 7 volts less positive). Equally important, but what's not grasped, is that it does not stop conducting till its Base is at or near its Emitter - just as an NPN does not stop conducting till its Base is at or near its Emitter. The PNP conducts when its Base is at a potential less positive (more negative) than its Emitter. The PNP is presented with an electrode connected to a negative voltage ( gasp!), which provokes apoplexy and panic, or it gets mentioned in passing ('.there are PNP transistors, too, but you won't see them much and I don't like them, so let's move on.') and so is left to languish in obscurity, something to be avoided ( ley de hielo.) Looking back at some textbooks, they're never presented inside the '+V and GND' paradigm. Understanding a 'high-side switch' supposes knowledge of PNP transistor operation.Ĭomparatively, the PNP is a little understood device. I found a great tool, it's at -Īnother invaluable GPS site, most everything about anything NMEA -Ī lot of people feel, howbeit superficially, that they 'get' NPN operation - the NPN conducts when its Base is at a potential more positive than its Emitter. The number after the asterisk is the checksum. is Line Feed, ASCII $0A (or 0x0a), or is Carriage Return, ASCII $0D (or 0x0d), or The sentences can be disabled from the SiRF Demo, but if the GPS is left unpowered for 2-3 days then it reverts to stock config.Ī) Make the config part of the initialisation in the programme. Heretofore, I've used the SiRF Demo, solely, to configure the '688 with. My only interest for a certain project is the RMC sentence.

Had it on the oscilloscope, over the supply range of 3 to 5V, TX was 0/3V signal.

Pmb-648 gps sirf arduino