no propeller chip found, chip over heating, 400mA consumed
jahm
Posts: 3
looking for some genius out there to give me a hand,
i have the propeller proto USB, some time ago, the micro USB connection broke, so i replaced it, since some of the pads on the PCB came off i had to connect some of the cable straight into the "On board USB to serial" IC, it was then working fine for a couple of months, one day i connected it to a power supply and tied loading the EEPROM and the error msg came up, no chip found ... com 3, then i notice that the current used by the proto was 400mA, none of the pins where connected to anything, yet it seemed as if there was a short circuit to happen, the chip got very hot in a matter of minutes so i disconnected it, i kept testing the board, changed USB port, checked the voltage from both voltage regulators (5v and 3.3v) everything seems fine except that on the second regulator (3.3v) the resistance between pin 2 and 3 is only 10 Ohms, i dont think tht is correct. i found the schematic of the board and started slowly removing some components to see if one of them is burned but till now no luck, the only thing i can think of is that maybe is my fixed connection to the USB port the problem, but it should still not give me such a high current, plus the LEDs they all work fine, when the USB is connected the LED blink and when i turn on the proto the green LED is also on, i would like to know, can i just power up the chip with 3.3v and see if its just the chip that broke or a component? when looking at the datasheet from the chip, there are many VDD inputs, but doesn specify which one to use to power up the chip, any help there?
cheers
i have the propeller proto USB, some time ago, the micro USB connection broke, so i replaced it, since some of the pads on the PCB came off i had to connect some of the cable straight into the "On board USB to serial" IC, it was then working fine for a couple of months, one day i connected it to a power supply and tied loading the EEPROM and the error msg came up, no chip found ... com 3, then i notice that the current used by the proto was 400mA, none of the pins where connected to anything, yet it seemed as if there was a short circuit to happen, the chip got very hot in a matter of minutes so i disconnected it, i kept testing the board, changed USB port, checked the voltage from both voltage regulators (5v and 3.3v) everything seems fine except that on the second regulator (3.3v) the resistance between pin 2 and 3 is only 10 Ohms, i dont think tht is correct. i found the schematic of the board and started slowly removing some components to see if one of them is burned but till now no luck, the only thing i can think of is that maybe is my fixed connection to the USB port the problem, but it should still not give me such a high current, plus the LEDs they all work fine, when the USB is connected the LED blink and when i turn on the proto the green LED is also on, i would like to know, can i just power up the chip with 3.3v and see if its just the chip that broke or a component? when looking at the datasheet from the chip, there are many VDD inputs, but doesn specify which one to use to power up the chip, any help there?
cheers
Comments
Darn, That doesn't sound good.
All four Vdd pins need 3.3V and all the ground pins need to be connected (I've read many times here, this is important).
You should be able to apply 3.3V to the 3.3V power line and it will take care getting the power to all Vdd pins.
I'm not sure how to test the chip without actually loading a program into it. There's a schematic to program the Propeller from a RS-232 connection using a couple of transistors in the data sheet.
If you have a Prop Plug I could tell you how to use it to communicate with the Prop. I've cut the USB portion out of several USB Proto Boards and added header pins in their place. I use the USB portion as a DIY Prop Plug.
QuickStart boards are an easy way to get back to using the Propeller. They use the USB connection for power as well as communication and only cost $25.
BTW, Welcome to the forum.
i checked all the VDD and VSS pins, and they all have the correct value(3.3v-0v) but still the 400mA dont think is normal specially because its not running any LED or motor, so u are advising me to skip the "On board USB to serial" ic and try to communicate with the PC by using a Prop Plug?
i live in the netherlands, so parallax components are not easy to get, but i do work at a RnD facility, so i do have the tools to work something out.
thanks again for ur time
cheers
Jef
If you had one (Prop Plug) available it might be worth checking to see if the Prop still works. I'm not sure if a Prop Plug would work while the onboard USB chip is still connected.
As I think about this a bit more, it sure seems like there's something else going on here.
Those Proto Boards have a ground plan between a lot of the prototyping holes. I've used too much solder around a wire that shorted to the ground plan (through the solder mask). Maybe the excess current is caused by a short. Are all your solder spots nice and neat? Could any be causing a short?
Just trying to think of problems I've had that might help until "some genius" comes along.
The FTDI chip is what controls the USB LED's blinking when you plug in the cable, the Prop could be dead and those LEDs still blink when plugging the cable in from a PC. So, it can be possibly assumed that the USB chip is working and is partially connected to the PC. On the pins that are at 10ohms, if both are outputs, and one goes high and the other stays low, that could damage the Prop. If both are inputs, and the short it on the board, that should not damage the Prop, although you still have a problem with on the PCB somewhere most likely.
by experience i know hot is not a problem as long as current levels make sense, but too hot and 400mA, tricky one, i know its not a complete short circuit cuz otherwise my current limiter would have kicked in and the voltage dropped, whats funny its sometimes the current its 430mA and other times is 380mA is always changing i guess influence from the heat and when i said about 10ohms between pins i meant the 3.3v regulator pin 1(GND) and pin 2 (3.3 output), also i just notice that the first regulator (5v) is also getting hotter than usual, i guess im gonna have to replace the chip and hope that was it, otherwise im gonna take it apart and recycle them!!!
thanks