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Shift register missing bits (discuss.tchncs.de)

submitted 11 months ago* (last edited 11 months ago) by quiescentcurrent@discuss.tchncs.de to c/askelectronics@discuss.tchncs.de

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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&lt;17; i++){

    byte upper_byte = input_bin >> 8;
    byte lower_byte = input_bin &amp; 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.

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[–] Kalcifer@lemm.ee 0 points 11 months ago (1 children)

I don't follow what you mean.

[–] FuzzChef@feddit.de 0 points 11 months ago* (last edited 11 months ago)

I think what he refers to is that you seem to do a bitwise or for the second line instead of the bitwise and.