Hi all.
I’m having trouble with a couple prototype PCBs I just received that use the IMP003 (schematic and top PCB layer attached). Applying power to the IMP causes the green LED to blink (only the green, no RED at all) on for 1.25 sec and off for 0.5 sec. This scheme doesn’t seem to correspond to any of the Blinkup status codes. The green LED continues to flash at the stated rate during Blinkup, which has no effect on the state of the WLAN_POWER_EN. Neither of the modules have been connected to a network - they are brand new.
I have successfully designed, manufactured and tested two versions of PCB with IMP003 before and the new design essentially replicates the previous (maybe it was dumb luck first time).
PCB SN1:
0.7V on LED_GREEN (this seems to be the highest voltage reached when the LED_GREEN pin is active), LED does not light up as far as I can tell. There is evidence of capacitance on the leading and trailing edges of the signal on LED_GREEN. It’s possible I buggered the LED_GREEN pin of the IMP003 on this PCB as 0R resistors were mistakenly installed as R6 and R7 on both PCBs; this was found during testing and the resistors were subsequently replaced with 100R. I’m not so much concerned with the weird LED_GREEN signals on this PCB as the rate and lack of LED_RED signal.
WLAN_POWER_EN is not active at any time after applying power (not even for the shortest amount of time), so power is never applied to the VDD_PA/VDD_WLAN pins or to the flash which is on the WLAN power net.
Signals on the OSC32 lines are as expected (same as on working IMP003 PCBs).
There is 0VDC on the OPTO_BIAS line (3.3VDC on working IMP003 PCBs).
The IMP003 pulls ~72mA continuously.
PCB SN2:
~3V on LED_GREEN when LED is operating. There is always 0V on LED_RED.
WLAN_POWER_EN is not active at any time after applying power (not even for the shortest amount of time), so power is never applied to the VDD_PA/VDD_WLAN pins or to the flash which is on the WLAN power net.
There is 0.324VDC on OSC32_IN, 0V on OSC32_OUT.
There is 3.3VDC on OPTO_BIAS and 0.58V on OPTO_IN.
The IMP003 pulls 24mA with green LED off and up to 40mA with the green LED on.
So to my questions:
Why is the green LED only flashing when the IMP003 is powered up?
What is the meaning of the 1.25 sec on/0.5 sec off green LED sequence?
Any ideas why I might be getting these kinds of results?
Is there anything else I should look at that might indicate why these IMP003 aren’t working?
Cheers,
Franc