The Steinhart-Hart equation was changed in code long ago to the B-parameter equation. Rename references to it and the interface accordingly. The `s-h` command is now `b-p`. The reason the name "B-Parameter" equation was chosen over "Beta-Parameter" was due to its easier searchability.
14 KiB
Firmware for the Sinara 8451 Thermostat
- Continuous Integration
- Download latest firmware build: ELF BIN
Building
Reproducible build with Nix
Thermostat firmware is packaged using the Nix Flakes system. Install Nix 2.4+ and enable flakes by adding experimental-features = nix-command flakes
to nix.conf
(e.g. ~/.config/nix/nix.conf
).
Once you have Flakes enabled, you can use nix build
to build the firmware.
Development environment
Clone this repository and with Nix Flakes enabled, use the following commands:
nix develop
cargo build --release
The resulting ELF file will be located under target/thumbv7em-none-eabihf/release/thermostat
.
Alternatively, you can install the Rust toolchain without Nix using rustup; see the rust
variable in flake.nix
to determine which Rust version to use.
Debugging
Connect SWDIO/SWCLK/RST/GND to a programmer such as ST-Link v2.1. Run OpenOCD:
openocd -f interface/stlink.cfg -f target/stm32f4x.cfg
You may need to power up the programmer before powering the device. Leave OpenOCD running. Run the GNU debugger:
gdb target/thumbv7em-none-eabihf/release/thermostat
(gdb) source openocd.gdb
Flashing
There are several options for flashing Thermostat. DFU requires only a micro-USB connector, whereas OpenOCD needs a JTAG/SWD adapter.
dfu-util on Linux
- Install the DFU USB tool (dfu-util).
- Convert firmware from ELF to BIN:
llvm-objcopy -O binary target/thumbv7em-none-eabihf/release/thermostat thermostat.bin
(you can skip this step if using the BIN from Hydra) - Connect to the Micro USB connector to Thermostat below the RJ45.
- Add jumper to Thermostat v2.0 across 2-pin jumper adjacent to JTAG connector.
- Cycle board power to put it in DFU update mode
- Push firmware to flash:
dfu-util -a 0 -s 0x08000000:leave -D thermostat.bin
- Remove jumper
- Cycle power to leave DFU update mode
st.com DfuSe tool on Windows
On a Windows machine install st.com DfuSe USB device firmware upgrade (DFU) software. link.
- add jumper to Thermostat v2.0 across 2-pin jumper adjacent to JTAG connector
- cycle board power to put it in DFU update mode
- connect micro-USB to PC
- use st.com software to upload firmware
- remove jumper
- cycle power to leave DFU update mode
OpenOCD
openocd -f interface/stlink.cfg -f target/stm32f4x.cfg -c "program target/thumbv7em-none-eabihf/release/thermostat verify reset;exit"
Network
Connecting
Ethernet, IP: 192.168.1.26/24
Use netcat to connect to port 23/tcp (telnet)
rlwrap 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
ADC input data is provided in reports. Query for the latest report with the command report
. See the Reports section below.
TCP commands
Send commands as simple text string terminated by \n
. Responses are
formatted as line-delimited JSON.
Syntax | Function |
---|---|
report |
Show latest report of channel parameters (see Reports section) |
output |
Show current output settings |
output <0/1> max_i_pos <amp> |
Set maximum positive output current, clamped to [0, 2] |
output <0/1> max_i_neg <amp> |
Set maximum negative output current, clamped to [0, 2] |
output <0/1> max_v <volt> |
Set maximum output voltage, clamped to [0, 4] |
output <0/1> i_set <amp> |
Disengage PID, set fixed output current, clamped to [-2, 2] |
output <0/1> polarity <normal/reversed> |
Set output current polarity, with 'normal' being the front panel polarity |
output <0/1> pid |
Let output current to be controlled by the PID |
center <0/1> <volt> |
Set the MAX1968 0A-centerpoint to the specified fixed voltage |
center <0/1> vref |
Set the MAX1968 0A-centerpoint to measure from VREF |
pid |
Show PID configuration |
pid <0/1> target <deg_celsius> |
Set the PID controller target temperature |
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 <amp> |
Set mininum output |
pid <0/1> output_max <amp> |
Set maximum output |
b-p |
Show B-Parameter equation parameters |
b-p <0/1> <t0/b/r0> <value> |
Set B-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 [0/1] |
Restore configuration for channel all/0/1 from flash |
save [0/1] |
Save configuration for channel all/0/1 to flash |
reset |
Reset the device |
dfu |
Reset device and enters USB device firmware update (DFU) mode |
ipv4 <X.X.X.X/L> [Y.Y.Y.Y] |
Configure IPv4 address, netmask length, and optional default gateway |
fan |
Show current fan settings and sensors' measurements |
fan <value> |
Set fan power with values from 1 to 100 |
fan auto |
Enable automatic fan speed control |
fcurve <a> <b> <c> |
Set fan controller curve coefficients (see Fan control section) |
fcurve default |
Set fan controller curve coefficients to defaults (see Fan control section) |
hwrev |
Show hardware revision, and settings related to it |
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 when USB 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 parameters for the B-Parameter equation.
Set the base temperature in degrees celsius for the channel 0 thermistor:
b-p 0 t0 20
Set the resistance in Ohms measured at the base temperature t0:
b-p 0 r0 10000
Set the Beta parameter:
b-p 0 b 3800
50/60 Hz filtering
The AD7172-2 ADC on the SENS inputs supports simultaneous rejection of
50 Hz ± 1 Hz and 60 Hz ± 1 Hz (dB). Affecting sampling rate, the
postfilter rate can be tuned with the postfilter
command.
Postfilter rate | Rejection | Effective sampling rate |
---|---|---|
16.67 Hz | 92 dB | 8.4 Hz |
20 Hz | 86 dB | 9.1 Hz |
21.25 Hz | 62 dB | 10 Hz |
27 Hz | 47 dB | 10.41 Hz |
Thermo-Electric Cooling (TEC)
- Connect TEC module device 0 to TEC0- and TEC0+.
- Connect TEC module device 1 to TEC1- and TEC1+.
- The GND pin is for shielding not for sinking TEC module currents.
When using a TEC module with the Thermostat, the Thermostat expects the thermal load (where the thermistor is located) to cool down with a positive software current set point, and heat up with a negative current set point.
If the Thermostat is used for temperature control with the Sinara 5432 DAC "Zotino", and is connected via an IDC cable, the TEC polarity may need to be reversed with the output <ch> polarity reversed
TCP command.
Testing heat flow direction with a low set current is recommended before installation of the TEC module.
Limits
Each MAX1968 TEC driver has analog/PWM inputs for setting output limits.
Use the output
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 |
i_set |
Amperes | (Not a limit; Open-loop mode) |
Example: set the maximum voltage of channel 0 to 1.5 V.
output 0 max_v 1.5
Example: set the maximum negative current of channel 0 to -3 A.
output 0 max_i_neg 3
Example: set the maximum positive current of channel 1 to 3 A.
output 0 max_i_pos 3
Open-loop mode
To manually control TEC output current, set a fixed output current with
the output
command. Doing so will disengage the PID control for that
channel.
Example: set output current of channel 0 to 0 A.
output 0 i_set 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:
output 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. Reports are JSON objects
with the following keys.
Key | Unit | Description |
---|---|---|
channel |
Integer | Channel 0 , or 1 |
time |
Seconds | Temperature measurement time |
interval |
Seconds | Time elapsed since last report update on channel |
adc |
Volts | AD7172 input |
sens |
Ohms | Thermistor resistance derived from adc |
temperature |
Degrees Celsius | B-Parameter conversion result derived from sens |
pid_engaged |
Boolean | true if in closed-loop mode |
i_set |
Amperes | TEC output current |
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 |
Note: Prior to Thermostat hardware revision v2.2.4, the voltage and current readouts i_tec
and tec_i
are noisy without the hardware fix shown in this PR.
PID Tuning
The thermostat implements a PID control loop for each of the TEC channels, more details on setting up the PID control loop can be found here.
Fan control
Fan control commands are available for thermostat revisions with an integrated fan system:
fan
- show fan stats:fan_pwm
,abs_max_tec_i
,auto_mode
,k_a
,k_b
,k_c
.fan auto
- enable auto speed controller mode, where fan speed is controlled by the fan curvefcurve
.fan <value>
- set the fan power with the value from1
to100
and disable auto mode. There is no way to completely disable the fan. Please note that power doesn't correlate with the actual speed linearly.fcurve <a> <b> <c>
- set coefficients of the controlling curvea*x^2 + b*x + c
, wherex
isabs_max_tec_i/MAX_TEC_I
, a normalized value in range [0,1], i.e. the (linear) proportion of current output capacity used, on the channel with the largest current flow. The controlling curve is also clamped to [0,1].fcurve default
- restore fan curve coefficients to defaults:a = 1.0, b = 0.0, c = 0.0
.