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Line Follower 16-ch × micro:bit (MakeCode extension)

Back to Line Follower 16-ch

The universal I2C edition of the Line Follower 16-ch works with BBC micro:bit V1 / V2 through the MakeCode extension pxt-mbc-sensors v2 (which speaks MBC I2C protocol v2). Installation and hardware notes (3.3 V, power): micro:bit overview.

SPIKEEV3Arduino I2CmBlockMATRIXmicro:bit

Important

Extension v2 is not yet verified on hardware; block names follow the published release: https://github.com/contactmbcrobot/pxt-mbc-sensors

Wiring

Line Follower 16-ch × micro:bit
Sensor micro:bit
SDA（RX） P20
SCL（TX） P19
VCC micro:bit 3V (external 5 V recommended on batteries)
GND GND

Reporter blocks

Block Returns Id Meaning
line position -16~+16 01 which channel the line is under: −16 (far left) to +16 (far right), 0 = centre; seen from behind the robot, negative = left (normally ±15; ±16 only for 200 ms after the line leaves the outermost channel)
fine line position -100~+100 02 sub-channel position: −100 to +100, 0 = centre, negative = left (same sign as line position)
line width 0~16 路 03 number of channels on the line, 0~16; 0 = no line
line segments 0~8 04 number of separate line segments: 0 = lost, 1 = one line, ≥2 = fork / crossing
line bitmap 0~65535 bit 05 bit0 = channel 1 (left) … bit15 = channel 16; 1 = that channel sees the line
last exit direction -16~+16 06 where the line was before it was lost: −16 to +16 (negative = left); keeps the last value
line threshold 1~99 07 reflect threshold for 'on line', 1~99, default 40 (firmware shipped before 2026-11-03: 50); set with E4
line calibration count 0~255 次 08 number of calibrations completed since power-on (button calibrations included)
channel [1~16] reflect 0~100 10~1F calibrated reflect of channel 116, 0100 (channel 1 = left); ids 10~1F

More blocks (yes / no, events)

Block Related value
line is seen 04
on line [lost] 04
channel 1 is on the line 05
line follower is calibrating 08

Command blocks

Block Id Meaning
line follower follow [black] line E0 follow a black line (default); RAM only, back to the default after reset
line follower follow [white] line E1 follow a white line (F3 b1 = 1); RAM only, back to the default after reset
line follower calibrate [current reading is black] E2 store the current reading as black (sensor over the black line), ~50 ms; saved to EEPROM
line follower calibrate [current reading is white] E3 store the current reading as white (sensor over the white surface), ~50 ms; saved to EEPROM
line follower set threshold 50 E4 threshold 1~99 (RAM only, back to 40 after reboot); on SPIKE an out-of-range value returns failed (state 2)
line follower calibrate [auto (sweep for 5 s)] E7 sweep the sensor across black line and white surface for 5 s; min/max become the references; F3 b2 = 1 meanwhile

Status

bit Name Meaning
b0 ready (ready) always 1
b1 white line mode (whiteMode) 1 = following a white line
b2 calibrating (calibrating) E2/E3/E7 in progress; new calibration commands are ignored
b3 line lost (lost) segment count = 0
b4 fork (fork) segment count ≥ 2
b5 mirrored (reversed) E9 = 1 (sensor mounted backwards, left/right mirrored)

JavaScript

if (!(mbc.waitReady(0x16, 3000))) {
    basic.showIcon(IconNames.No)   // nothing answers: check wiring and power
}
basic.forever(function () {
    basic.showNumber(mbc.linePosition())   // line position
    basic.pause(100)
})

Sources and assumptions

Generated by _build/gen-reference.mjs from _build/protocol/line16.json (single source of truth, transcribed from the 2026-10-21 protocol decisions).

  • B-11：細位置 02 與線位置 01 同號（負 = 左）；韌體 F16:1290 註解寫反，程式碼同號（IR:11 為準）。
  • B-12：E7 五秒動態校準補回（v1 的 0x20=0x01），定案表沒列。
  • EV3：模式 0~2 鎖住；模式 3 原本不送 → 16 bit 位元圖；模式 4 原本不送 → 同模式 2；模式 5 ID 格式 B（共用函式）。
  • SPIKE：0/5/7/9 鎖住，14、6 維持不動；教育版模式 0 的 16 路光值是 2-bit（玩具版 1-bit），跟 8 路的 4-bit 不同；byte 815 補 0（#65 已改，使用者保留）；模式 9 排法照盤點（四路 4-bit 一個 int16，v6 = 位元圖）；模式 8 v[0] 改 ID|hw[0]<<8。
  • 線段數 04 範圍：定案沒寫，16 路最多 8 段（交錯壓線），採 0~8。
  • mBlock 舊版：MBC_MBLOCK_LEGACY=1 時逐 byte 同 2026-10-21 統一後韌體（0x01 位置、0x02 線寬、n<<4|03 反向兩路壓一 byte、0x07 細位置 0~200），0x0B 回 1（B-1）。
  • Flash：C031 硬體鎖 28 KB，I2C 版餘 848 B；不夠時照 B-17 順序瘦身，JSON 不受影響。
  • The extension reads Int16LE and pauses 2 ms after writing the id (D5); with no sensor answering, reporters return 0 and yes / no blocks return false.
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