Chapter 173: Three Seconds Without Power

The delivery arrived on Sunday afternoon. Inside a grayish-yellow bubble mailer were a wide-input DC-DC module, two industrial-grade SD cards, and a handful of jumper wires. Lin Chen sliced through the tape with a utility knife and tipped the parts out onto a chipped wooden table. A multimeter, soldering iron, rosin, and desoldering pump stood in a neat row. He pulled up a chair and rested his left foot on a plastic stool nearby. A third medicated patch was already fixed to his ankle. The dull ache that followed the anesthesia’s fade rolled in like a tide, drilling into the seams of his calf bones in rhythmic waves. He steadied his breathing and fixed his attention on the soldering iron’s tip.

He removed the old power board and cut the input wires. The pins on the wide-input module were thicker than the original, requiring the pads to be re-ground. White smoke rose from the rosin, its pungent odor mingling with the damp mustiness of the rental room. Tweezers in his left hand, temperature control in his right, the solder wire melted on the iron’s tip and quickly enveloped the pins. The first one: a cold joint. He desoldered it and started over. The second: solid and full. Habitually, he jotted a note in his notebook: Risk of cold joint on pin 3; reinforce with extra solder. This wasn’t his first hardware modification, but each time felt like walking a tightrope. Code could be rolled back; a bad solder joint meant a dead board. At a cost of 120 RMB, he couldn’t afford a mistake.

With the hardware connected, he powered it on for testing. The multimeter showed that as the input voltage fluctuated between 9V and 24V, the output held steady at 5.1V. He inserted an SD card, opened a terminal, and began writing the power-loss cache logic. Python’s try...except blocks couldn’t catch a hard power cut; he had to rely on OS signals or a watchdog timer. He switched to C to write a lightweight daemon that communicated with the main controller via serial port. The logic was straightforward: every 500 milliseconds, the main program wrote to a ring buffer on the SD card. The moment voltage dropped below the threshold, the watchdog would trigger, force-flushing the buffer to the SD card before cutting the load. Upon reboot, the main program would read the checksum block at the end of the SD card to patch any missing timestamps.

The time in the bottom-right corner of the screen jumped to 2:00 AM. He rubbed his dry eyes, stood up, and made a bowl of braised beef instant noodles. He poured in boiling water and stirred the noodle block with a plastic fork. Opening his ledger, he put a checkmark next to “Hardware Upgrade.” Three deductions had already been made from the 8,000 RMB advance payment: his brother’s sodium valproate for next month (1,200), his mother’s amlodipine (85), and his own pain patches and ice packs (60). The remainder had to stretch until the second milestone of the performance agreement. He ate slowly, swallowing the noodles without tasting them, merely refueling mechanically. The numbness in his foot had crept up to his knee. He stood and took two steps, bearing weight on his right leg while his left hovered, as if stepping on cotton. He couldn’t sit for long, nor stand. He had to finish the stress test before his body completely gave out.

Back at the desk, he connected an adjustable power supply to simulate a factory voltage sag. He dropped the voltage straight from 24V to 9V, held it for three seconds, then brought it back to 24V. The terminal screen went black for an instant, and the fan spun down. Three seconds later, the system rebooted. Logs scrolled across the screen: [INFO] Watchdog triggered. Power loss detected. [INFO] Reading cache from SD card... [INFO] 3.2 seconds of data recovered. Checksum: OK. The data stream picked up again without a single gap. He stared at the screen, didn’t smile, and simply let out a long breath. The three seconds of power loss had been filled.

He created a new folder named V3.1_Release_Tue. He packaged the compiled daemon, configuration files, and SD read/write scripts together. Then he drafted a deployment manual: 1. Back up logs before powering down; 2. Recalibrate the threshold after replacing the power module; 3. Run continuously for 72 hours, logging the false positive rate every hour. He printed it out and slipped it into a compartment inside the shockproof case. Outside, the sky began to pale. An early-shift bus rumbled over the asphalt, its engine groaning heavily. He packed away his tools, let the soldering iron cool, and covered it with a dust cloth. His left foot was too swollen to fit into his usual sneakers, so he swapped them for a pair of old rubber shoes a size larger, lacing them tightly to brace the ankle.

His phone vibrated. A text from Old Chen: Meet at the factory gate at 8:00 AM Tuesday. The expert team is bringing three data recorders. Your numbers need to match theirs. Lin Chen replied: Understood. Terminal upgraded, cache module ready. He hit send. Shouldering the shockproof case, he locked the door behind him. The motion-sensor lights in the stairwell flickered on and off in sequence with his footsteps. He knew the real test wouldn’t be in the code, but in the grease, the vibrations, and the aging equipment on the shop floor that never played by the book. Seventy-two hours. A 99.5% data integrity rate. Miss it by even one percentage point, and the performance agreement would trigger a breach clause.

At the bus stop, he glanced down at his phone’s calendar. Tuesday. Forty-eight hours until the experts arrived. He ran his fingers over the handle of the shockproof case; the metal edge was cold. Inside his shoe, his left foot throbbed with a dull heat—a sign the inflammation was spreading. He had to get the system mounted on the production line before the pain spiraled completely out of control. And the grounding wire on the factory’s old stamping press had already shown signs of degraded insulation during last week’s inspection. The voltage fluctuations were just the surface. The real undercurrent was still running deep below.