Reflow-A-Tron

Overview

This is a firmware repo for a reflow controller board that is currently in my eagle-stuff repository. The code is all C++ but without dynamic allocation as to not run the risk of having to deal with dynamic memory. The controller is fairly simple. It features a thermocouple sensor which is read over SPI. Serial communications are handled through a UART to an FTDI USB to serial converter. Control of the output triac is done using software PWM; I goofed on the port selection when doing the schematic .

Interface

The control interface to the board is serial at 9600 baud. The protocol is line based and overall fairly simple.

Sending A Command

Sending commands to the controller consists of a command followed by a set of arguments. The command and the arguments, if any, are separated by a | symbol.

• command|arg1,arg2,agr3,...

The controller after receiving a command with respond with either ok or nok. The former is an indicator that the command was successful and the later that the command was not successful.

The controller will also periodically send messages indicating it's current status as well as if any faults occur.

Available Commands

1. set_coef|kp,ki,kd - This sets the coefficients for the PID controller.

• kp - The proportional coefficient in Q15
• ki - The integral coefficient in Q15
• kd - The derivate coefficient in Q15

2. clear_profile - This clears the currently stored profile.
3. add_segment|target_temp,ramp_rate,time_s - This adds another segment to to the reflow profile with the given parameters

• index - The index of these parameters in the reflow profile
• target_temp - The target temp integer for the segment in Q12
• ramp_rate - The number of seconds per degree C
• time_s - The number of seconds we should spend in this segment

4. start - Start controlling to the
5. stop - Stop controlling the output
6. reset - Resets the entire controller

Returned Information

1. status|current_temp,current_setpoint,pwm_duty_cycle - Sent periodically while the controller is running

• current_temp - The current temperature in the oven in counts
• current_setpoint - The current temperature set point being controlled to in counts
• pwm_duty_cycle - The current PWM duty cycle in counts

2. profile|index,elapsed_time,segment_elapsed_time - Sent periodically during the execution of a reflow profile

• index - The current profile segment being executed
• elapsed_time - The time in seconds that the current profile has been executing
• segment_elapsed_time - The time in seconds that the current segment has been executing

3. fault|reason - Sent immediately after a fault has occurred

• reason - A string indicating the reason for the fault

Conversions

• Temp
  • counts to °C - For any temp in counts the equation is: (counts * 1023) / 4096
• Coefficients
  • float to counts - Multiply float by 2^15, the integer portion is the counts value.