thermostat/README.md

# Firmware for the Sinara 8451 Thermostat

- [x] [Continuous Integration](https://nixbld.m-labs.hk/job/mcu/thermostat/thermostat)
- [x] Download latest firmware build: [ELF](https://nixbld.m-labs.hk/job/mcu/thermostat/thermostat/latest/download/1) [BIN](https://nixbld.m-labs.hk/job/mcu/thermostat/thermostat/latest/download/2)


## Building

### Reproducible build with Nix

Thermostat firmware is packaged using the [Nix](https://nixos.org) 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:

```shell
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 manifest file pulled 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:
```shell
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:
```shell
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](https://st.com) DfuSe USB device firmware upgrade (DFU) software. [link](https://www.st.com/en/development-tools/stsw-stm32080.html).
- 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
```shell
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)
```sh
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 current input                                                            |
| `pwm`                                      | Show current PWM settings                                                     |
| `pwm <0/1> max_i_pos <amp>`                | Set maximum positive output current, clamped to [0, 2]                        |
| `pwm <0/1> max_i_neg <amp>`                | Set maximum negative output current, clamped to [0, 2]                        |
| `pwm <0/1> max_v <volt>`                   | Set maximum output voltage, clamped to [0, 4]                                 |
| `pwm <0/1> i_set <amp>`                    | Disengage PID, set fixed output current, clamped to [-2, 2]                   |
| `pwm <0/1> polarity <normal/reversed>`     | Set output current polarity, with 'normal' being the front panel polarity     |
| `pwm <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                                                            |
| `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 [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 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
```

### 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 `pwm <ch> polarity reversed` TCP command.

Testing heat flow direction with a low set current is recommended before installation of the TEC module.

## Resistive Heater

When using resistive heaters with the Thermostat, ensure that the thermal load has sufficient cooling, and connect the heater to TEC0- and TEC0+ or TEC1- and TEC1+.

Then, set `max_i_neg` and `output_min` to 0 A with `pwm <ch> max_i_neg 0` and `pid <ch> output_min 0`, and make sure that `output_max` is non-negative.

### 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      |
| `i_set`     | Amperes | (Not a limit; Open-loop mode) |

Example: set the maximum voltage of channel 0 to 1.5 V.
```
pwm 0 max_v 1.5
```

Example: set the maximum negative current of channel 0 to -3 A.
```
pwm 0 max_i_neg 3
```

Example: set the maximum positive current of channel 1 to 3 A.
```
pwm 0 max_i_pos 3
```

### 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 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:
```
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. Reports are JSON objects
with the following keys.

| Key            | Unit            | Description                                          |
| ---            | :---:           | ---                                                  |
| `channel`      | Integer         | Channel `0`, or `1`                                  |
| `time`         | Seconds         | 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                                   |
| `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: With Thermostat v2 and below, the voltage and current readouts `i_tec` and `tec_i` are noisy without the hardware fix shown in [this PR][https://git.m-labs.hk/M-Labs/thermostat/pulls/105].

## 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](./doc/PID%20tuning.md).

## Fan control

Fan control commands are available for thermostat revisions with an integrated fan system:
1. `fan` - show fan stats: `fan_pwm`, `abs_max_tec_i`, `auto_mode`, `k_a`, `k_b`, `k_c`.
2. `fan auto` - enable auto speed controller mode, where fan speed is controlled by the fan curve `fcurve`.
3. `fan <value>` - set the fan power with the value from `1` to `100` 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.
4. `fcurve <a> <b> <c>` - set coefficients of the controlling curve `a*x^2 + b*x + c`, where `x` is `abs_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].
5. `fcurve default` - restore fan curve coefficients to defaults: `a = 1.0, b = 0.0, c = 0.0`.