new to prop some hardware questions about usb/power/crystal/eprom

rwgast_logicdesign

ok so im pretty new to electronics design but im looking forward to building a prop pc from scratch seems fairly straight forward but i have a few questions concerning data transfer and power.

first off looking through the manual you can solder a $1.30 usb plug or even a cable to the chip.. so why are people paying 14 dollars for a prop plug? second would it be slower to use a db9 connector and a serial to usb cable? this solution sounds a little bit more versital, not something i intend to do just curious.

as far as power goes this is where im going to need a bit of help. i had dc theory a long time ago but only learned to solve circuts with transistors and capacitors, never ic's and transistors. what im looking to do is hopefully just use the power from the usb to power the board.now this is 5 volts and i wamt to use a 2 chip set up initially so i will need two 3.3 regulators and the supporting components correct? as far as the regulators go they can handle 9 volts correct? i see 9 volt batteris powering stuff in pictures. im also a bit curious about using the 6.25 crystal to oc but im not sure the chip will run stable and how that effects the power. everytime i find li ks to good oc threads there broken..

last semi related question is abkut eprom i know there are other ways to store data but for my personal reasons i wohld like more eprom room. is there a way to wire two togather so they make double the space and look like one unit to the prop? is this just as easy as wiring in parallel? also an i just buy a bigger chip spmewhere what kind of specifications do i need to dfollow. alot of proc documentation is on coding is there a good beginners hardware refrence tbat has tutorials based on the prop?

Mike Green

1) For programming, you need some kind of serial port to the PC. Some Prop boards just provide the relevant I/O pins to a connector and the PropPlug or equivalent takes care of all the USB stuff. Some Prop boards have all this built into the board in the form of an FTDI USB to serial adapter chip and the few passive support components needed. You can power the Prop from USB and I suggest looking at the schematic for the QuickStart board for one example of how to do this properly. There are some potential "gotchas" and starting with a known good example is always best. You could use a MAX3232 to provide the 3.3V logic to RS-232 voltage conversions and use an external USB to RS232 adapter or old-fashioned PC serial port via a DB-9 connector.

2) Overclocking the Propeller (crystal > 5MHz) is possible, but you really have to design and build for it and the PCB layout is crucial for reliable operation. It's not for a beginner.

3) The Propeller normally uses the first 32K of an EEPROM attached to I/O pins 28/29. You can use a 64K EEPROM or a 128K EEPROM, but only the first 32K will normally be used. There are a number of Propeller programs that will allow you to use the additional EEPROM for data. Look in the Object Exchange for examples ("Basic_I2C_Driver" is one). There are also program loaders that can be run from the first 32K of EEPROM and can load programs from other parts of the EEPROM(s) ("FemtoBasic" can do this). I2C EEPROMs normally allow for up to 512K on a pair of I/O pins. This can be provided via a combination of 64K or 128K EEPROMs. A 32K EEPROM acts like a 64K EEPROM with the upper half missing.