Hi all,
I’m setting up a custom CNC (experimental rig with a belt-driven X axis and ballscrew Y axis) using a Jackpot3 from Elecrow (purchased January 20, 2026). Running into a persistent TMC UART issue and would appreciate any input.
The problem:
On every boot, all configured axes fail driver detection:
[MSG:ERR: X Axis TMC driver not detected - expected 0x21 got 0x0]
[MSG:ERR: Y Axis TMC driver not detected - expected 0x21 got 0x0]
The motors do move when jogging, just with wrong distances (consistent with missing UART microstepping config — appears to run in standalone mode).
What I’ve tried:
- Firmware: Tested both FluidNC v4.0.1 (shipped) and downgraded to v3.9.9 via web installer — same error on both
- Power sequence: Confirmed 24V fully disconnected and reconnected without USB attached — error persists
- USB isolation: Ran
$SSwith no USB connected, only 24V — still not detected - Slot swap: Moved motor to Z slot and changed addr to 2 in config — still not detected. Rules out individual slot failure, points to UART bus being dead across all slots
- Motors confirmed connected: StepperOnline Nema 17 (2A, 59Ncm) on both X and Y, motors respond to jog commands
- Board confirmed powered: Drivers get warm, green LED lit
Likely cause:
I may have plugged in motor cables while 24V was live — I’ve since learned this can damage TMC drivers.
Current $SS output (v3.9.9, no USB):
[MSG:INFO: UART1 Tx:gpio.0 Rx:gpio.4 RTS:NO_PIN Baud:115200]
[MSG:INFO: I2SO BCK:gpio.22 WS:gpio.17 DATA:gpio.21]
[MSG:INFO: tmc_2209 UART1 Addr:0 ... Step:I2SO.2 Dir:I2SO.1]
[MSG:INFO: tmc_2209 UART1 Addr:1 ... Step:I2SO.5 Dir:I2SO.4]
[MSG:ERR: X Axis TMC driver not detected - expected 0x21 got 0x0]
[MSG:ERR: Y Axis TMC driver not detected - expected 0x21 got 0x0]
Questions:
- Given that addr:0, addr:1, and addr:2 all fail — is this definitely dead TMC chips, or could there still be a fixable UART bus issue I’m missing?
- Is there any way to verify the UART bus itself (gpio.0/gpio.4) is functional short of an oscilloscope?
- For now the machine moves in standalone mode — are there any risks beyond overheating (already putting heatsinks on) that I should watch out for while I sort out a replacement?
Thanks in advance.
my current config
board: Jackpot TMC2209
name: MPCNC
meta: 11-29-2023 RyanZ
planner_blocks: 32
stepping:
engine: I2S_STATIC
idle_ms: 255
pulse_us: 4
dir_delay_us: 1
disable_delay_us: 0
uart1:
txd_pin: gpio.0
rxd_pin: gpio.4
rts_pin: NO_PIN
baud: 115200
mode: 8N1
axes:
shared_stepper_disable_pin: NO_PIN
x:
steps_per_mm: 320
max_rate_mm_per_min: 8000
acceleration_mm_per_sec2: 400
max_travel_mm: 350
soft_limits: false
homing:
cycle: 1
positive_direction: false
mpos_mm: 0
feed_mm_per_min: 300
seek_mm_per_min: 1500
settle_ms: 500
seek_scaler: 1.1
feed_scaler: 1.1
motor0:
limit_neg_pin: gpio.39
limit_pos_pin: NO_PIN
limit_all_pin: NO_PIN
hard_limits: false
pulloff_mm: 5
tmc_2209:
uart_num: 1
addr: 0
cs_pin: NO_PIN
r_sense_ohms: 0.11
run_amps: 0.7
hold_amps: 0.4
microsteps: 16
run_mode: StealthChop
homing_mode: StealthChop
use_enable: false
step_pin: i2so.2
direction_pin: i2so.1:low
disable_pin: NO_PIN
y:
steps_per_mm: 400
max_rate_mm_per_min: 3000
acceleration_mm_per_sec2: 200
max_travel_mm: 350
soft_limits: false
homing:
cycle: 2
positive_direction: false
mpos_mm: 0
feed_mm_per_min: 300
seek_mm_per_min: 1500
settle_ms: 500
seek_scaler: 1.1
feed_scaler: 1.1
motor0:
limit_neg_pin: gpio.34
limit_pos_pin: NO_PIN
limit_all_pin: NO_PIN
hard_limits: false
pulloff_mm: 5
tmc_2209:
uart_num: 1
addr: 1
cs_pin: NO_PIN
r_sense_ohms: 0.11
run_amps: 0.68
hold_amps: 0.5
microsteps: 8
run_mode: StealthChop
homing_mode: StealthChop
use_enable: false
step_pin: i2so.5
direction_pin: i2so.4
disable_pin: NO_PIN
i2so:
bck_pin: gpio.22
data_pin: gpio.21
ws_pin: gpio.17