Turning off motor brake with M950

[DuetWiz1122]

I have a motor brake wired to an HCL expansion board. I want to turn it on and off manually and am trying to do it through M950 and M42 commands:

M950 P123.0 C"out0";
M42 P123.0 S0.0 ; set 50% PWM on GPIO port 0

When I run this I get:
"Error: M950 parameter P is too high" and "Error: M42 parameter P too high"

Would appreciate any suggestions or ever different commands that may turn off a brake manually...thanks!!

[jay_s_uk]

@DuetWiz1122 you would set the P value to 0 assuming this is the first P output you've setup. The CAN address goes in the C part e.g. C"123.out0"