Propeller chip...suddenly not found

benjaminshinobi

I was doing the exercises in the propeller manual, and was trying to get the video ones to work. All was going fine when suddenly the Prop is not being recognized.

The set up I had was on a breadboard with the Prop Plug. All the voltages look fine. And there was another thread I saw about a similar topic and adjusted the latency in the Device Manager.

The Prop Plug light is flashing when I plug it in, and when I press F7 or F10 to check the port/compile the code.

Also to note, for some reason for me, the chip wasn't being recognized at 3.3V (I did a set up with just some resistors forming a voltage divider from a 7805, I don't know if that was a bad idea), and was only working for me with 5v. I saw another post that the chip is "tolerant" of 5v so I figured this was okay just to do the exercises.

If any could let me know if I'm doing anything else elementary wrong that would be great.

Could the chip be messed up?

thanks.

Cobalt

Its very possible that you damaged your chip, running it at 5 volts was fine at first, but it may have finally given out.
Since your prop plug still lights up when you plug it in, try another propeller chip. If you don't have another one, you should probably go ahead and order one

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while alive = 1
wakeup
program(propeller)
eat(3)
sleep(7)

benjaminshinobi

Alright figured...I got the prop PRM with the socketed chip. Also, I could test with the serial port if something is somehow weird with the usb drivers.

Have there been other people noticing the chip not being recognized at 3.3v?

benjaminshinobi

also thanks for you prompt reply

Mike Green

A voltage divider off a 5V regulated supply is a bad idea. The current requirements of a Propeller (or most microprocessors) varies widely. The supply voltage to the Propeller would also vary widely above and below 3.3V as it draws more or less current from the voltage divider. The Propeller starts becoming damaged above 4.0V and it stops working below 2.7V.

Paul Baker

Voltage dividers only work if no current is drawn from the center tap, voltage dividers work by using ohms law and the current flowing through the resistors establishing the center voltage. Divert current from that node and the voltage at the node drops. Since the amount of current the Propeller needs varies by several orders of magnitude, there is no way to produce a constant 3.3V over the operation of the Propeller. I don't think you've damaged the Propeller, you just voltage starved it so it wouldn't work. As a general rule, you never place a resistor in the path between the supply and the chip (except sub 1 ohm resistance to measure current draw).

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Paul Baker
Propeller Applications Engineer

Parallax, Inc.

benjaminshinobi

I know it was a pretty elementary question, but thanks again for your prompt replies, great to know there is such a good community behind these products.