7.6 KiB
Firmware for the Sinara 8451 Thermostat
Building
Debian-based systems (tested on Ubuntu 19.10)
- install git, clone this repository
- install rustup
rustup toolchain install nightly
rustup update
rustup target add thumbv7em-none-eabihf --toolchain nightly
rustup default nightly
cargo build --release
The resulting ELF file will be located under target/thumbv7em-none-eabihf/release/thermostat
Network
Connecting
Ethernet, IP: 192.168.1.26/24
Use netcat to connect to port 23/tcp (telnet)
nc -vv 192.168.1.26 23
telnet clients send binary data after connect. Enter \n once to invalidate the first line of input.
Reading ADC input
Set report mode to on for a continuous stream of input data.
The scope of this setting is per TCP session.
Commands
| Syntax | Function |
|---|---|
report |
Show current input |
report mode |
Show current report mode |
report mode <off/on> |
Set report mode |
pwm |
Show current PWM settings |
pwm <0/1> max_i_pos <ratio> |
Set PWM duty cycle for max_i_pos to ampere |
pwm <0/1> max_i_neg <ratio> |
Set PWM duty cycle for max_i_neg to ampere |
pwm <0/1> max_v <ratio> |
Set PWM duty cycle for max_v to volt |
pwm <0/1> <volts> |
Disengage PID, set i_set DAC to ampere |
pwm <0/1> pid |
Set PWM to be controlled by PID |
center <0/1> <volts> |
Set the MAX1968 0A-centerpoint to volts |
center <0/1> vref |
Set the MAX1968 0A-centerpoint to measure from VREF |
pid |
Show PID configuration |
pid <0/1> target <value> |
Set the PID controller target |
pid <0/1> kp <value> |
Set proportional gain |
pid <0/1> ki <value> |
Set integral gain |
pid <0/1> kd <value> |
Set differential gain |
pid <0/1> output_min <value> |
Set mininum output |
pid <0/1> output_max <value> |
Set maximum output |
pid <0/1> integral_min <value> |
Set integral lower bound |
pid <0/1> integral_max <value> |
Set integral upper bound |
s-h |
Show Steinhart-Hart equation parameters |
s-h <0/1> <t0/b/r0> <value> |
Set Steinhart-Hart parameter for a channel |
postfilter |
Show postfilter settings |
postfilter <0/1> off |
Disable postfilter |
postfilter <0/1> rate <rate> |
Set postfilter output data rate |
load |
Restore configuration from EEPROM |
save |
Save configuration to EEPROM |
reset |
Reset the device |
ipv4 <X.X.X.X> |
Configure IPv4 address |
USB
The firmware includes experimental support for acting as a USB-Serial peripheral. Debug logging will be sent there by default (unless build with logging via semihosting.)
Caveat: This logging does not flush its output. Doing so would hang indefinitely if the output is not read by the USB host. Therefore output will be truncated once buffers are full.
Temperature measurement
Connect the thermistor with the SENS pins of the device. Temperature-depending resistance is measured by the AD7172 ADC. To prepare conversion to a temperature, set the Beta parameters for the Steinhart-Hart equation.
Set the base temperature in degrees celsius for the channel 0 thermistor:
s-h 0 t0 20
Set the resistance in Ohms measured at the base temperature t0:
s-h 0 r0 10000
Set the Beta parameter:
s-h 0 b 3800
Thermo-Electric Cooling (TEC)
Connect the Peltier device to the TEC0/1-/+ outputs.
Limits
Each of the MAX1968 TEC driver has analog/PWM inputs for setting output limits.
Use the pwm command to see current settings and maximum values.
| Limit | Unit | Description |
|---|---|---|
max_v |
Volts | Maximum voltage |
max_i_pos |
Amperes | Maximum positive current |
max_i_neg |
Amperes | Maximum negative current |
| Amperes | Output current control |
Example: set the maximum voltage of channel 0 to 1.5 V.
pwm 0 max_v 1.5
Open-loop mode
To manually control TEC output current, omit the limit parameter of
the pwm command. Doing so will disengage the PID control for that
channel.
Example: set output current of channel 0 to 0 A.
pwm 0 0
PID-stabilized temperature control
Set the target temperature of channel 0 to 20 degrees celsius:
pid 0 target 20
Enter closed-loop mode by switching control of the TEC output current of channel 0 to the PID algorithm:
pwm 0 pid
LED indicators
| Name | Color | Meaning |
|---|---|---|
| L1 | Red | Firmware initializing |
| L3 | Green | Closed-loop mode (PID engaged) |
| L4 | Green | Firmware busy |
Reports
Use the bare report command to obtain a single report. Enable
continuous reporting with report mode on. Reports are JSON objects
with the following keys.
| Key | Unit | Description |
|---|---|---|
channel |
Integer | Channel 0, or 1 |
time |
Milliseconds | Temperature measurement time |
adc |
Volts | AD7172 input |
sens |
Ohms | Thermistor resistance derived from adc |
temperature |
Degrees Celsius | Steinhart-Hart conversion result derived from sens |
pid_engaged |
Boolean | true if in closed-loop mode |
i_set |
Amperes | TEC output current |
vref |
Volts | MAX1968 VREF (1.5 V) |
dac_value |
Volts | AD5680 output derived from i_set |
dac_feedback |
Volts | ADC measurement of the AD5680 output |
i_tec |
Volts | MAX1968 TEC current monitor |
tec_i |
Amperes | TEC output current feedback derived from i_tec |
tec_u_meas |
Volts | Measurement of the voltage across the TEC |
pid_output |
Amperes | PID control output |