14
Shift register missing bits (discuss.tchncs.de)
submitted 1 year ago* (last edited 1 year ago) by quiescentcurrent@discuss.tchncs.de to c/askelectronics@discuss.tchncs.de

Hey friends,

I have a two daisy chained shift registers (74AHC595) which are controlled via an ESP32. I want to set one output to high at a time before switching to the next.

The code seems to work, but the outputs O_9 and O_10 are not staying high (zoom) after setting them, whereas all the other ones are working fine. This is the used code snipped:

pinMode(SHIFT_OUT_DATA, OUTPUT);
pinMode(SHIFT_OUT_CLK, OUTPUT);
pinMode(SHIFT_OUT_N_EN, OUTPUT);
pinMode(SHIFT_OUT_LATCH, OUTPUT);

digitalWrite(SHIFT_OUT_N_EN, LOW);

uint16_t input_bin = 0b1000000000000000;

for(int i=0; i<17; i++){

    byte upper_byte = input_bin >> 8;
    byte lower_byte = input_bin & 0x00FF;

    digitalWrite(SHIFT_OUT_LATCH, LOW);
    shiftDataOut(SHIFT_OUT_DATA, SHIFT_OUT_CLK, MSBFIRST, lower_byte);
    shiftDataOut(SHIFT_OUT_DATA, SHIFT_OUT_CLK, MSBFIRST, upper_byte);
    usleep(10);
    digitalWrite(SHIFT_OUT_LATCH, HIGH);

    delay(10)
    input_bin = input_bin>>1;
} 

Is there anything I'm doing wrong, or any idea on where the problem may lie? I've already tried looking for shorts and other error sources, but the design was manufactured on a PCB and no assembly issues are noticeable.

you are viewing a single comment's thread
view the rest of the comments

Good idea, I've tried usleep after all lines, but no change..

this post was submitted on 27 Sep 2023
14 points (100.0% liked)

Ask Electronics

3173 readers
1 users here now

For questions about component-level electronic circuits, tools and equipment.

Rules

1: Be nice.

2: Be on-topic (eg: Electronic, not electrical).

3: No commercial stuff, buying, selling or valuations.

4: Be safe.


founded 2 years ago
MODERATORS