[teo1747]

The first part of M7's robot on the floor: its motors and the drivers that power them from a battery.

What it adds

The motor

• dc_motor, an analog primitive (core/analog/motor.c, SPEC-004): a brushed DC motor solved with the circuit.
  • Winding: resistance and inductance in series with the back EMF.
  • Rotor: inertia, friction, and a gearbox's ratio and efficiency, with a load torque on the shaft.
  • The current and the speed are two extra unknowns of the island.
  • Powered at t = 0, it starts at its stall current; turned by its load, it generates.
• emblink/pololu_3073_gearmotor: Pololu's 50:1 Micro Metal Gearmotor HPCB 6V (extended shaft), its constants from Pololu's specifications at 6 V. Inductance and inertia are estimates, declared in the fidelity.

The drivers

• h_bridge, an analog primitive (core/analog/hbridge.c, SPEC-004): one bridge of an integrated motor driver.
  • Output stage. FETs from VM and to the sense return, as on-resistances that follow VM, with body diodes. A motor slows as its battery sags and coasts through the diodes.
  • Inputs. Read as voltages through Schmitt thresholds and pulldowns. They are absolute, or fractions of a logic supply on VCC (vcc_ref).
  • Truth tables. DRV8833, TB6612FNG and L293D.
  • Timing. Deglitch, propagation delay, and high-to-low and low-to-high dead times.
  • Protection. UVLO on VM or VCC, slow-decay current chopping on a sense resistor, and overcurrent shutdown with retry and an open-drain FAULT.
  • Sleep and wake: nSLEEP, or STBY as standby.
• emblink/h_bridge: the primitive as a part.
• emblink/drv8833: TI's DRV8833, with the values of datasheet SLVSAR1E.
• emblink/tb6612fng: Toshiba's TB6612FNG.
  • Its datasheet's H-SW control table.
  • 0.5 Ω outputs (upper + lower) and 1 V diodes.
  • Thresholds at 0.3/0.7 VCC with 200 kΩ pulldowns.
  • 50/230 ns dead times, the 1.9/2.2 V VCC lockout, and 1 µA standby.
  • SSOP24's doubled pins are separate pins joined inside.
• French text for every part.
• Engine changes.
  • An analog primitive takes up to 16 terminals (8 before).
  • A composite's pin declared nc needs no port.

Evidence

• Motor fixtures: no-load, start, stall, reverse. The constants give a best-efficiency point within 6 % of Pololu's.
• h_bridge fixtures:
  • forward: 4.83 V across 10 Ω
  • timing: 1.1 µs propagation, a 300 ns pulse lost to the deglitch, the dead time
  • uvlo
• DRV8833 fixtures:
  • motor: 640 rpm at 6 V
  • chopping: 0.38 to 0.40 A with 0.5 Ω on AISEN
  • overcurrent: nFAULT low, then the 1.35 ms retry
  • sleep: 1.6 µA
  • awake: 1.7 mA
• TB6612FNG fixtures:
  • drive: the gearmotor at about 640 rpm, with channel B braking
  • pwm_brake
  • standby: under 1 µA
  • vcc_thresholds: 2.0 V is low at VCC = 5 V; the 1.9 V lockout
• Tests.
  • The full dev ctest passed (72/72) before the TB6612FNG.
  • With the TB6612FNG, test_analog, test_catalog, test_engine, catalog_fr, tools_unittests and the 16 motor and driver fixtures pass on dev, ci-clang, ci-tcc (clean build) and asan.
  • validate.py --all, catalog_text check, check_docs and check_banned are clean.
• Merged with main after Build experimental original ESP32 execution, memory and I/O foundations #115.

Not yet

• The L293D part on the primitive.
• Thermal shutdown and switching edges.
• The encoder, and the robot's body in the world.