I am using the RPi_GPIO library in a python shell to read a raw wireless signal using the wait_for_edge() function in a loop like so:
while True:
GPIO.wait_for_edge(26, GPIO.RISING)
print 'R'
GPIO.wait_for_edge(26, GPIO.FALLING)
print 'F'
Meanwhile in another python shell on the same machine, I am doing a cheesy PWM by switching GPIO 21 HIGH/LOW and calling sleep() in between like this:
while True
GPIO.output(21, GPIO.HIGH)
sleep(20)
GPIO.output(21, GPIO.LOW)
sleep(20)
My goal was just to verify that I had everything wired up and could send/receive signal. Maybe 30 seconds in, I got a message in both shells that said:
Message from syslogd@raspb2 at May 19 21:35:26 ...
kernel:[ 9675.681566] Disabling IRQ #49
This is what I see in /proc/interrupts:
CPU0 CPU1 CPU2 CPU3
16: 0 0 0 0 ARMCTRL 16 bcm2708_fb dma
24: 262 0 0 0 ARMCTRL 24 DMA IRQ
25: 2887 0 0 0 ARMCTRL 25 DMA IRQ
32: 6527881 0 0 0 ARMCTRL 32 dwc_otg, dwc_otg_pcd, dwc_otg_hcd:usb1
49: 200000 0 0 0 ARMCTRL 49 3f200000.gpio:bank0
50: 0 0 0 0 ARMCTRL 50 3f200000.gpio:bank1
65: 44 0 0 0 ARMCTRL 65 ARM Mailbox IRQ
66: 2 0 0 0 ARMCTRL 66 VCHIQ doorbell
75: 1 0 0 0 ARMCTRL 75
79: 0 0 0 0 ARMCTRL 79 3f804000.i2c
80: 0 0 0 0 ARMCTRL 80 3f204000.spi
83: 17 0 0 0 ARMCTRL 83 uart-pl011
84: 19653 0 0 0 ARMCTRL 84 mmc0
99: 81407 60633 23147 50785 ARMCTRL 99 arch_timer
474: 15968 0 0 0 pinctrl-bcm2835 26 gpiolib
FIQ: usb_fiq
IPI0: 0 0 0 0 CPU wakeup interrupts
IPI1: 0 0 0 0 Timer broadcast interrupts
IPI2: 59304 52831 74083 54061 Rescheduling interrupts
IPI3: 7 6 9 12 Function call interrupts
IPI4: 3 4 1 2 Single function call interrupts
IPI5: 0 0 0 0 CPU stop interrupts
IPI6: 0 0 0 0 IRQ work interrupts
IPI7: 0 0 0 0 completion interrupts
Err: 0
IRQ #49 appears to be gpio:bank0 (I never knew there were different banks for the GPIO). I am guessing that I have overrun a buffer or something while trying to read and write so rapidly. Maybe both of these pins are on the same bank and I could us a different pin for one of the loops that is on the other bank. Unfortunately a quick google search did not turn up a reference for which pins are on which bank. I don't think this is a show-stopper but now my interest is peaked. Anyone have this problem before or have some insight into what it is? What is the maximum speed at which I can/should read/write on GPIO pins?
