Add LP5562EVM USB-I2C control tool, document reverse-engineered protocol
Reverse-engineered the MSP430 serial protocol on the LP5562EVM: - I<addr><reg> reads, O<addr><reg><data> writes, status 00=OK / 02=NAK - EN pin must be jumpered to VDD (MSP430 doesn't drive it after reset) - CONFIG (0x0B) is write-only, W_CURRENT (0x09) not writable via bridge - LED cycling verified: all 4 channels respond to direct PWM control Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
This commit is contained in:
michael
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# xblink Project Status
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**Current Milestone**: M1 — LED Smoke Test (code ready, needs USB cable to flash)
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**Last Updated**: 2026-03-03
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**Current Milestone**: M1 — LED Smoke Test (I2C verified via EVM USB bridge, XIAO M0 flash pending)
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**Last Updated**: 2026-03-05
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---
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@@ -23,7 +23,8 @@
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- [x] Create `src/led/mod.rs` with re-exports
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- [x] Update `main.rs` with I2C init + GPIO EN + LP5562 direct PWM test
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- [x] Verify `cargo build --release` compiles
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- [ ] Flash and verify RGBW LED channels on LP5562EVM
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- [x] Verify LP5562 I2C control via EVM USB-to-I2C bridge (`tools/lp5562_evm.py`)
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- [ ] Flash XIAO M0 and verify RGBW LED channels with Rust firmware
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### M2: Engine Patterns
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90
docs/plans/2026-03-05-lp5562evm-protocol.md
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docs/plans/2026-03-05-lp5562evm-protocol.md
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# LP5562EVM MSP430 Serial Protocol (Reverse-Engineered)
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**Date**: 2026-03-05
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**Status**: Working — I2C read/write verified, LEDs cycling
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## Hardware
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- **EVM**: LP5562EVM (SNVU203A) with MSP430F5510 USB-to-I2C bridge
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- **USB**: CDC device, VID:PID `2047:0300`, appears as `/dev/ttyACM0`
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- **Baud**: 115200, 8N1
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- **EN pin**: Must be jumpered to VDD externally — MSP430 does NOT drive EN after reset
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## Protocol
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Commands are ASCII text, no line terminator needed. The MSP430 parses character-by-character and responds after receiving the expected number of hex digits.
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### Commands
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| Command | Format | Response | Description |
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|---------|--------|----------|-------------|
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| `?` | `?` | `TI Sep 12 2012 08:19:25\n` | Firmware version |
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| `I` (read) | `I<addr2><reg2>` | `SS DD OK\n` | I2C register read |
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| `O` (write) | `O<addr2><reg2><data2>` | `SS OK\n` | I2C register write |
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| `R` (read) | `R<addr2><reg2>` | `OK\n` | I2C read (no data returned) |
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| `A` | `A` | `OK\n` | Unknown (possibly internal) |
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- `addr2`: 2-char hex I2C 7-bit address (e.g., `30` for LP5562)
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- `reg2`: 2-char hex register address
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- `data2`: 2-char hex data byte
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- `SS`: 2-char hex status (`00` = success, `02` = I2C NAK / device not responding)
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- `DD`: 2-char hex data byte read from device
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### Other Command Prefixes
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These accept input but are not fully understood:
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| Prefix | Chars consumed | Response | Guess |
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|--------|---------------|----------|-------|
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| `S` | 2 hex chars | (silent) | GPIO/setting control? |
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| `V` | 2 hex chars | (silent) | Voltage/value setting? |
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| `C` | 6 hex chars | `OK\n` | Config/control? |
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| `P` | 8 hex chars | (silent or `OK`) | Program memory? |
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### Invalid Commands
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Single characters not recognized as command prefixes return `?\n`. Extra characters after a complete command also return `?\n` each.
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## LP5562 Register Quirks via EVM Bridge
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| Register | Address | Writable | Read-back | Notes |
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|----------|---------|----------|-----------|-------|
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| ENABLE | 0x00 | Yes | Yes | |
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| OP_MODE | 0x01 | Yes | Yes | |
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| B/G/R/W_PWM | 0x02-0x05 | Yes | Yes | |
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| B/G/R_CURRENT | 0x06-0x08 | Yes | Yes | |
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| W_CURRENT | 0x09 | No | Always 0x00 | Write ACKs but no effect |
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| CONFIG | 0x0B | Functional | Always 0x00 | Write-only: takes effect but reads 0 |
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| STATUS | 0x0C | N/A | Yes | Read-only |
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| LED_MAP | 0x70 | Yes | Yes | Default 0x39 (engines mapped) — must set to 0x00 for direct PWM |
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## Working Init Sequence
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```
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O300DFF # Reset (write 0xFF to RESET register)
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# Wait 500ms
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O300040 # ENABLE = 0x40 (chip_en)
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# Wait 1ms (>500us startup)
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O300B01 # CONFIG = 0x01 (internal oscillator) — write-only
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O307000 # LED_MAP = 0x00 (all channels = I2C direct)
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O300632 # B_CURRENT = 0x32 (5mA)
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O300732 # G_CURRENT = 0x32
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O300832 # R_CURRENT = 0x32
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# W_CURRENT left at default 0xAF (0x09 not writable)
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O3002FF # B_PWM = 0xFF (full brightness)
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```
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## LED Hardware on EVM
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- **D1**: LRTB_G6SF (Osram RGB LED) — driven by B/G/R channels
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- **D2-D5**: LW Q38E (Osram white LEDs) — driven by W channel
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- **D7**: LSL296 (red status LED) — driven by MSP430, not LP5562
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- All LP5562 LED outputs pass through **P5** header (4x2 dual-row with jumpers)
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## Key Discovery: EN Pin
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The LP5562 EN pin is controlled by the MSP430's GPIO (EN-UC), connected through the P6 header. After USB reset, the MSP430 holds EN low. The TI Windows GUI software presumably sends a command to assert EN, but we were unable to identify which serial command does this.
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**Workaround**: Jumper EN directly to VDD (3.3V) on P1 or P6 header. This is acceptable because in the final xblink design, EN is controlled by a wired-AND circuit (MCU GPIO + hall sensor), not the EVM's MSP430.
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Without EN high, all I2C reads return status `02` (NAK) with data `00`.
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280
tools/lp5562_evm.py
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280
tools/lp5562_evm.py
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#!/usr/bin/env python3
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"""
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LP5562EVM USB-I2C bridge control tool.
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Controls the LP5562 LED driver via the EVM's MSP430 USB-to-I2C bridge.
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The MSP430 presents as a CDC serial device (/dev/ttyACM0).
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Protocol (reverse-engineered):
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Read: I<addr2><reg2> → "SS DD OK\n" (SS=00 success, DD=data hex)
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Write: O<addr2><reg2><data2> → "SS OK\n" (SS=00 success)
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Info: ? → "TI <date>\n"
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Prerequisites:
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- LP5562 EN pin must be held high (jumper EN to VDD on EVM P1/P6 header).
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The MSP430 does NOT drive EN after reset.
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- CONFIG register (0x0B) is write-only via this bridge — writes take effect
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but reads always return 0x00. Internal oscillator must be explicitly set.
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- W_CURRENT (0x09) cannot be written via this bridge (LP5562 quirk or
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MSP430 limitation). White channel uses reset default (0xAF = 17.5mA).
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Usage:
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./lp5562_evm.py dump # Read all registers
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./lp5562_evm.py init # Enable chip + internal clock + direct PWM
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./lp5562_evm.py color R G B W # Set RGBW PWM values (0-255)
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./lp5562_evm.py off # All LEDs off
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./lp5562_evm.py cycle # Cycle through RGBW channels
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./lp5562_evm.py breathe # Breathing pattern demo
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"""
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import serial
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import sys
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import time
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PORT = '/dev/ttyACM0'
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BAUD = 115200
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LP5562_ADDR = 0x30
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# LP5562 register map
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REG_ENABLE = 0x00
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REG_OP_MODE = 0x01
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REG_B_PWM = 0x02
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REG_G_PWM = 0x03
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REG_R_PWM = 0x04
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REG_W_PWM = 0x05
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REG_B_CURRENT = 0x06
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REG_G_CURRENT = 0x07
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REG_R_CURRENT = 0x08
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REG_W_CURRENT = 0x09
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REG_CONFIG = 0x0B
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REG_STATUS = 0x0C
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REG_RESET = 0x0D
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REG_INT_GPO = 0x0E
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REG_LED_MAP = 0x70
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REG_NAMES = {
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0x00: 'ENABLE', 0x01: 'OP_MODE', 0x02: 'B_PWM',
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0x03: 'G_PWM', 0x04: 'R_PWM', 0x05: 'W_PWM',
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0x06: 'B_CURRENT', 0x07: 'G_CURRENT', 0x08: 'R_CURRENT',
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0x09: 'W_CURRENT', 0x0B: 'CONFIG', 0x0C: 'STATUS',
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0x0D: 'RESET', 0x0E: 'INT_GPO', 0x70: 'LED_MAP',
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}
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# ENABLE register bits
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CHIP_EN = 0x40
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LOG_EN = 0x80
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# CONFIG register bits
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CLK_INT = 0x01 # Internal oscillator
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# OP_MODE: engine modes (2 bits each: [7:6]=E3, [5:4]=E2, [3:2]=E1)
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MODE_DISABLED = 0b00
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MODE_LOAD = 0b01
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MODE_RUN = 0b10
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MODE_DIRECT = 0b11
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class LP5562EVM:
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def __init__(self, port=PORT, baud=BAUD):
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self.ser = serial.Serial(port, baud, timeout=0.5)
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time.sleep(0.1)
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self.ser.reset_input_buffer()
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def close(self):
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self.ser.close()
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def version(self):
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self.ser.reset_input_buffer()
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self.ser.write(b'?')
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time.sleep(0.2)
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return self.ser.read(256).decode('ascii', errors='replace').strip()
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def read(self, reg):
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"""Read LP5562 register. Returns data byte or raises on error."""
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self.ser.reset_input_buffer()
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self.ser.write(f'I{LP5562_ADDR:02X}{reg:02X}'.encode())
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time.sleep(0.15)
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resp = self.ser.read(256).decode('ascii', errors='replace').strip()
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parts = resp.split()
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if len(parts) < 3 or parts[-1] != 'OK':
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raise IOError(f"Read reg 0x{reg:02X} failed: {resp}")
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status = int(parts[0], 16)
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if status != 0:
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raise IOError(f"I2C NAK reading reg 0x{reg:02X} (status={status:02X}). Is EN pin high?")
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return int(parts[1], 16)
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def write(self, reg, val):
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"""Write LP5562 register."""
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self.ser.reset_input_buffer()
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self.ser.write(f'O{LP5562_ADDR:02X}{reg:02X}{val:02X}'.encode())
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time.sleep(0.15)
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resp = self.ser.read(256).decode('ascii', errors='replace').strip()
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parts = resp.split()
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if not parts or parts[-1] != 'OK':
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raise IOError(f"Write reg 0x{reg:02X}=0x{val:02X} failed: {resp}")
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status = int(parts[0], 16)
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if status != 0:
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raise IOError(f"I2C NAK writing reg 0x{reg:02X} (status={status:02X}). Is EN pin high?")
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def dump(self):
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"""Read and display all registers."""
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print("LP5562 Register Dump")
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print("=" * 40)
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for reg in sorted(REG_NAMES.keys()):
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try:
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val = self.read(reg)
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name = REG_NAMES[reg]
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print(f" 0x{reg:02X} {name:12s} = 0x{val:02X} ({val:3d}) {val:08b}")
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except IOError as e:
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print(f" 0x{reg:02X} {REG_NAMES[reg]:12s} = ERROR: {e}")
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def reset(self):
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"""Software reset the LP5562."""
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self.write(REG_RESET, 0xFF)
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time.sleep(0.5)
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def init(self, current_ma=5.0):
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"""Initialize LP5562 for direct PWM control."""
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# Reset to known state
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self.write(REG_RESET, 0xFF)
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time.sleep(0.5)
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# Enable chip
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self.write(REG_ENABLE, CHIP_EN)
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time.sleep(0.001) # >500us startup
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# Internal oscillator (write-only: reads back as 0x00, but takes effect)
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self.write(REG_CONFIG, CLK_INT)
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# All LEDs mapped to I2C direct control
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self.write(REG_LED_MAP, 0x00)
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# Set current for B/G/R (0-255 maps to 0-25.5mA, so 10 = 1mA)
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# W_CURRENT (0x09) is not writable via EVM bridge — uses default 0xAF
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current_val = min(255, max(0, int(current_ma * 10)))
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self.write(REG_B_CURRENT, current_val)
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self.write(REG_G_CURRENT, current_val)
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self.write(REG_R_CURRENT, current_val)
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print(f"LP5562 initialized: chip_en, internal osc, {current_ma:.1f}mA/ch (W=17.5mA default)")
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def set_color(self, r=0, g=0, b=0, w=0):
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"""Set RGBW PWM values (0-255)."""
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self.write(REG_R_PWM, r & 0xFF)
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self.write(REG_G_PWM, g & 0xFF)
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self.write(REG_B_PWM, b & 0xFF)
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self.write(REG_W_PWM, w & 0xFF)
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def off(self):
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"""All LEDs off."""
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self.set_color(0, 0, 0, 0)
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def cmd_dump(evm, args):
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ver = evm.version()
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print(f"EVM firmware: {ver}")
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print()
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evm.dump()
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def cmd_init(evm, args):
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current = float(args[0]) if args else 5.0
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evm.init(current_ma=current)
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evm.dump()
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def cmd_color(evm, args):
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if len(args) < 3:
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print("Usage: color R G B [W]")
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return
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r, g, b = int(args[0]), int(args[1]), int(args[2])
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w = int(args[3]) if len(args) > 3 else 0
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evm.set_color(r, g, b, w)
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print(f"Set color: R={r} G={g} B={b} W={w}")
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def cmd_off(evm, args):
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evm.off()
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print("All LEDs off")
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def cmd_cycle(evm, args):
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step = float(args[0]) if args else 0.5
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pwm = 255
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print(f"Cycling RGBW channels ({step}s per step). Ctrl+C to stop.")
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try:
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while True:
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evm.set_color(0, 0, pwm, 0) # Blue
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print(" Blue")
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time.sleep(step)
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evm.set_color(0, pwm, 0, 0) # Green
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print(" Green")
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time.sleep(step)
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evm.set_color(pwm, 0, 0, 0) # Red
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print(" Red")
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time.sleep(step)
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evm.set_color(0, 0, 0, pwm) # White
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print(" White")
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time.sleep(step)
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evm.set_color(pwm, pwm, pwm, pwm) # All
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print(" All on")
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time.sleep(step)
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evm.off()
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print(" Off")
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time.sleep(step)
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except KeyboardInterrupt:
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evm.off()
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print("\nStopped.")
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def cmd_breathe(evm, args):
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"""Software breathing effect (ramp PWM up and down)."""
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print("Breathing pattern on blue channel. Ctrl+C to stop.")
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try:
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while True:
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# Ramp up
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for i in range(0, 256, 4):
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evm.set_color(0, 0, i, 0)
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time.sleep(0.02)
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# Ramp down
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for i in range(255, -1, -4):
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evm.set_color(0, 0, max(0, i), 0)
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time.sleep(0.02)
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time.sleep(0.3)
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except KeyboardInterrupt:
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evm.off()
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print("\nStopped.")
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COMMANDS = {
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'dump': cmd_dump,
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'init': cmd_init,
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'color': cmd_color,
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'off': cmd_off,
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'cycle': cmd_cycle,
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'breathe': cmd_breathe,
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}
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def main():
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if len(sys.argv) < 2 or sys.argv[1] not in COMMANDS:
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print("Usage: lp5562_evm.py <command> [args...]")
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print()
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print("Commands:")
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print(" dump Read all registers")
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print(" init [mA] Enable chip, set current (default 5mA)")
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print(" color R G B [W] Set RGBW PWM (0-255)")
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print(" off All LEDs off")
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print(" cycle [sec] Cycle through RGBW (default 0.5s)")
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print(" breathe Software breathing pattern")
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sys.exit(1)
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evm = LP5562EVM()
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try:
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COMMANDS[sys.argv[1]](evm, sys.argv[2:])
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finally:
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evm.close()
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if __name__ == '__main__':
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main()
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Reference in New Issue
Block a user