MARSLIFE Technical Report #3

Transcription

1 MARSLIFE Technical Report #3 The SMITH Control System and Control Software B. Broekhoven 1

2 1. Introduction The Sampling Microbes In The High atmosphere (SMITH) pump control subsystem provides control and monitoring of SMITH during ground testing and flight operations. SMITH is a bio-sampling payload designed to sample at 120,000 feet. The bio-sampling payload s design, hardware, and software allows for the payload to sample for microbiology in the stratosphere. The payload s pump control subsystem describes both the hardware necessary to physically control SMITH as well as the software which provides the logic and control over the hardware. The high level general requirements for the payload s pump control subsystem is to: 1) monitor and record temperatures for the sample and control pumps, 2) collect pressure, temperature, and humidity readings of SMITH s environment from the environmental acquisition subsystem, 3) monitor the rotations of the payload s engines, 4) check the status of intake and exhaust valves, 5) receive, validate, and execute preset commands sent to the payload from ground control, and 6) downlink a time stamped data record to ground control through the High Altitude Student Payload (HASP) with the pump status, all environmental data, and responses and errors to the command that was just received. The payload s environmental acquisition subsystem provides monitoring of SMITH s environment. The environmental acquisition subsystem contains both the hardware necessary to monitor SMITH s environment as well as the software which retrieves the payload s environmental data. This environmental data is sent to SMITH s pump control subsystem and sent down in the data record. The high level general requirement for the payload s environmental acquisition subsystem is it to collect pressure, temperature, and humidity readings of its environment. The general system that satisfies all the above requirements is shown in Figure 1. The pump control subsystem and environmental acquisition subsystem is comprised of two independent microcontroller stacks, one to control and monitor the pump control subsystem and the other to collect environmental data via the environmental acquisition subsystem. Each stack runs its own software and they communicate with each other via two MAX3107s connected by an RS-232 serial link. Both stacks use a BalloonSat board, as well as a communications board. In addition, the pump control subsystem uses a sensor board which contains the circuitry necessary to monitor the pump system while the environmental acquisition subsystem employs a board to collect environmental data. The pump control subsystem communicates with HASP via an RS-232 serial link to accept uplink commands and to downlink data. The microcontroller on board the BalloonSat boards is a Parallax BASIC Stamp. This BASIC Stamp is able to control different elements of SMITH, like the rotations per second (RPS) sensors, hall effect sensors, and record data as well as communicate with HASP through the communications board. The sensor board in the pump control subsystem allows for temperatures of both pumps to be recorded and monitored and 2

3 the sensor board in the environmental acquisition subsystem allows for the environment s pressure, temperature, and humidity to be recorded. A description of the hardware that enables these goals to be accomplished can be found in the MARSLIFE Technical Report #2. Figure 1: High level software design for both the pump and environmental microcontrollers Figure 1 shows the basic layout for the software of the pump control subsystem, the software of the environmental acquisition subsystem, and how the two subsystems interact. On power on, the microcontrollers both initialize their MAX3107s and sensors, then the pump control software waits for incoming commands from HASP while periodically sending data records to ground control and the environmental acquisition software waits for incoming commands 3

4 from the pump control microcontroller. When a command is received from HASP, the pump control software processes the command. After the command is processed, a data record is sent to the ground control. To do this, the pump control software sends a command to the environmental acquisition microcontroller to retrieve the environmental data. While the environmental acquisition software is retrieving the environmental data, the pump control software retrieves the payload status data and stores them in variables. After the environmental acquisition software retrieves the environmental data, it then sends the pressure, temperature, and humidity to the pump control software and the pump control software stores the data in variables and sends the data record to ground control. If there is no environmental data to be received from the environmental acquisition subsystem after five loops, then the pump control subsystem sends a data record to ground control without the environmental data. This is how the two stacks work together, however, other than this they are independent. The overall payload s software goal is to collect environmental data and control and monitor the pumps. 2. Pump Control Software A high level diagram of the pump control software is shown in Figure 2. On power on, the controller first creates a buffer of 20 bytes, which is used to store data records in. (In the flowcharts, each byte of the buffer is referred to by what it stores in that byte of the buffer, not the buffer.) After creating the buffer and other variables, the controller enters its initialization process as shown in Figure 2. 4

5 Figure 2: High level software design for the pump control microcontroller After initialization of the MAX3107s and the counters, the microcontroller is sent to the Set Time subroutine. In this subroutine, the controller reads the time from the real time clock and stores it in variables. After completing and exiting this subroutine, the controller then initializes the telemetry period to ten seconds, and then the controller enters a loop where it checks for incoming commands from HASP, validates the incoming commands, and forces a 5

6 data record if a command is received, valid or invalid. If no command is received, the loop will continue to calculate the time between the last data record sent to ground control and the current time. If this time difference exceeds the telemetry period, a data record is produced and downlinked to ground control. To do this, the pump control software sends a command to the environmental acquisition microcontroller requesting the environmental data. While the environmental acquisition software is retrieving the environmental data, the pump control software processes the payload status data. When the pump control software is done processing the payload status data, it retrieves the environmental, temperature, pressure, and humidity from the environmental acquisition software and then sends a data record to ground control. After the process, the loop would then repeat. This is the basics of the pump control software Initialization Figure 3 shows the subroutine for initializing two different MAX3107s. A MAX3107 is a chip that allows for communication between the two microcontrollers and HASP. Figure 3: Initalize MAX3107s 6

7 On power on, the controller initializes the MAX3107 used for HASP communication and then initializes the MAX3107 used for communication with the environmental acquisition software. To do this, the pump control software sets a temporary variable equal to the slave ID address for HASP and calls the Initialize MAX3107 subroutine and then does the same process using the slave ID address for the environmental acquisition MAX3107. Figure 4 shows the subroutine for initializing an individual MAX3107. Figure 4: Initalize individual MAX3107 The first step resets the MAX 3107and the second step then enables the chip for communication. The next step sets the clock source to be an external crystal oscillator. 7

8 The following step sets the lower register for baud rate to 4800 and then sets the higher register for baud rate to zero. The next step enables special character detection and auto software flow control. The last step then sets the word length to eight. Doing all this enables a MAX3107 to commutate to other MAX3107 chips using a baud rate of This chip allows distribution of SMITH s processes across the two microcontrollers. It also allows SMITH to function. After the initialization of the MAX3107s, the controller then initializes the pump rotational sensors. Figure 5 shows how to initialize these sensors. Figure 5: Initialize Counters In figure 5, both sensors are called through the I2C Bus Switch. Then the controller pauses 10ms. After this, each sensor is set to event mode. Setting the sensors to this mode allows for the counting of the pump s rotations. Then the sensors are paused and reset by writing zeros to the sensor s registers. Then the sensors are started again. 8

9 After initialization of the sensors, a buffer is created. This buffer consists of twenty bytes which stores all the payload and environmental data to be sent down to ground control. After creating the buffer, the controller enters the set time subroutine. This subroutine is shown in figure 6. Figure 6: Set Time The subroutine reads the current time from the real time clock and stores it into variables HASP Communication SMITH communicates with HASP for two reasons, to receive uplink commands and downlink data records. To receive commands, the pump control software will enter a loop where the microcontroller reads the register where the number of incoming bytes is stored in the MAX3107 from HASP. This process is shown in figure 7. 9

10 Figure 7: Check for and receive commands subroutine 10

11 The register where the number of incoming bytes is stored is called the RxFIFOLvl. If there are not seven bytes in the RxFIFOLvl, then the microcontroller pauses for five milliseconds and checks again after the pause to see if there are seven bytes in the RxFIFOLvl now. The BASIC Stamp will repeat this process a maximum of five times and then clear the RxFIFOLvl. However, if there are seven bytes in the RHR register, register where bytes are actually stored, then the return bit is set to one and the BASIC Stamp returns to the main program. If there are seven bytes in the HASP RHR register, the microcontroller reads in the first byte from the RHR register of the HASP MAX3107 and validates it. If this byte is valid, it reads in the second byte from the RHR register and repeats the process until all seven bytes are read and validated. If a byte is invalid, a corresponding hexadecimal value is set to the pump control error response variable and the BASIC Stamp exits the subroutine. Bytes three and four are the actual command sent from ground control and these bytes are just read straight into the corresponding variables and are validated in the process command subroutine. After the seven bytes are read in, the microcontroller clears the RxFIFOLvl again. To clear the RxFIFOLvl register, the software needs to read in the excess bytes to get rid of them. Figure 8 shows how to do this. 11

12 Figure 8: Clear RxFIFOLvl First the software sets the counts equal to zero and reads in the numbers of bytes from the RxFIFOLvl and sets this number equal to the temporary variable. If the temporary variable is greater than zero and if counts is smaller than 128 (the maximum bytes that can be stored), then the controller reads in a byte, rereads the number of bytes in the RxFIFOLvl, and updates counts by one. Once the condition fails, the software exits the subroutine and returns to the main loop. 12

13 The subroutine to downlink data records in shown in Figure 9. Figure 9: Downlink Data Subroutine To do this subroutine, the BASIC Stamp will downlink all the data stored in the buffer to ground control through HASP. These variables are delimited by commas. The first variables to be sent to ground control are the day, hour, minute, and second. The next variables to be sent down are the sample pump and motor temperature and the sample pump rotations per second (RPS) as shown in Figure 9. Next the control pump and motor temperature and the control RPS variables are sent down. Then the status bits variable is sent down followed by the environmental pressure, temperature, and humidity variables. The last command sent variables are sent down next followed by the telemetry period variable. Last the command response variable and two error variables, the first for error with the pump control software called CMD_SMITH_ERROR and the second for the environmental acquisition software called CMD_SUBR_ERROR, are sent down to ground control followed by a carriage return and a line feed. 13

14 2.3. Pump Monitor Once the command string has been validated, the pump control microcontroller checks to see if the actual command is valid. This is shown in figure 10. Figure 10: Process Command 14

15 The microcontroller enters a select case and compares the first byte of the stored command to the cases. If the command matches a case, the command is executed using the second byte of the command stored as the argument and a command response is set. If it does not match a case, the controller sets the pump control command error variable. Commands that can be executed consist of turning on or off the sample or control pump, opening or closing the sample or control intake valve, opening or closing the sample or control exhaust valve, turning and opening all the above listed at once, or turning off and closing all the above listed at once. These commands are executed by running high or low an I/O pin or multiple I/O pins and setting the command response variable. Other commands that can be executed are reinitializing any MAX3107 chip or changing the telemetry period for the payload. If the command is invalid, the SMITH response error variable will be set to a predetermined hexadecimal value. The command case to reinitialize a MAX3107 is shown in Figure 11. Figure 11: Reinitialize MAX 3107 subroutine 15

16 Depending on the second command byte sent from ground control, a different MAX3107 can be reinitialized. Next the command response variable is set to a predetermined hexadecimal value and then the microcontroller pauses 100ms. After the BASIC Stamp pauses, it returns to the main program Environmental Data Retrieval Once a command is executed, a record is forced to ground control as shown in figure 12. Figure 12: Send command to SUBR To do this, a command is sent to the environmental acquisition subsystem from the pump control microcontroller to produce the environmental pressure, temperature, and humidity data. After the command is sent, the microcontroller returns to the main loop. 16

17 2.5. Process Data Record While the environmental acquisition software is retrieving the environmental data, the pump control microcontroller goes on to read the current time from the real time clock and stores it in variables as shown in Figure 13. Figure 13: Process Data Record The BASIC Stamp then goes on and reads the ADC channels to get the temperatures of the sample and control engines and motors in counts and stores them in variables. After this, the microcontroller goes and stops the sample RPS sensor, reads the value of the sample RPS sensor into a variable, resets the sample RPS sensor to zero, and starts the RPS sensor again. This process is then repeated for the control RPS sensor. After the control RPS sensor is restarted, the microcontroller goes and reads the I2C I/O expander which has pins connected to the hall effect sensors, and sets the bits to the proper variable according to the reading of the I2C I/O expander. Then the BASIC Stamp reads the time from the real time clock and sets it to variables. After reading the time and recording its valves in variables, the microcontroller checks to see if there are three bytes in the RHR register from the environmental acquisition subsystem as shown in Figure

18 Figure 14: Receive SU Environmental Data If there are three bytes in the RHR register, the bytes are read into variables and the subroutine is exited. If there are not three bytes in the RHR register, the microcontroller pauses 150 milliseconds and checks for three bytes in the RHR register again. It repeats this process five times before it sets the environmental subsystem error response to a set hexadecimal value and exits the subroutine. 18

19 3. Environmental Acquisition Software On power on, the environmental acquisition software first initializes its MAX3107 and clears its RxFIFOLvl. After this, the program enters a loop as seen in Figure 15. Figure 15: High level software design for the environmental acquisition microcontroller 19

20 In this loop it first pauses for 500ms and then checks for a one byte command from the pump control subsystem. If there is a one byte command from pump control subsystem, the microcontroller reads in the command into a variable. If there is not a one byte command from pump control subsystem, the microcontroller clears the RxFIFOLvl and repeats the loop. These processes/subroutines are shown in previous diagrams. Refer to figures 4 and 8 for Initalize individual MAX3107 and ClearRxFIFOLvl flowcharts. Once the command is read in, the BASIC Stamp validates the command. If the command to reinitialize the MAX3107 is sent, the microcontroller enters the initialize MAX3107 subroutine. If the command to retrieve environmental data is received, the microcontroller enters a subroutine called GetData. In this subroutine, the BASIC Stamp starts the conversation with the ADC chip to read the ADC channels as shown if Figure 16. Figure 16: Get Data Subroutine 20

21 The microcontroller then reads the first channel of the ADC, which is the environmental temperature, stores it in a variable, and pauses 5ms. The BASIC Stamp then does the same process for the environmental pressure and humidity. Once all three channels are read, the controller sends these variables to the pump control subsystem in decimal format for the data record. It then exits the subroutine and returns to the main program. 4. Communications: Uplink Commanding and Data Downlink The uplink process allows the SMITH team to control various components of the payload from the ground. For SMITH to receive a command, the uplink command must be seven bytes long. The format for receiving a command is under the uplink commands section below. The downlink data process allows SMITH to send data records to ground control. This also means that SMITH did not have to store data on board and ground control could view real time data Uplink Commands All commands are sent up in hexadecimal numbers. Each command consists of two bytes. The command format to receive a command through HASP is as follows: Table 1: Byte Hex Value Description 1 01 Start of Heading (SOH) 2 02 Start of Text (STX) 3 command First byte of the command transmitted from the ground byte 1 4 command Second byte of the command transmitted from the ground byte End of Text (ETX) 6 0D Carriage Return (CR) 7 0A Line Feed (LF) Table 1: Command format for HASP 21

22 The following table is a table of all the possible commands SMITH can receive in hexadecimal values and what that command does. Table 2: Command from HASP to SMITH (byte one) Command from HASP to SMITH (byte two) What command does 0 1 Turn On Sample Pump 0 0 Turn Off Sample Pump 1 1 Open Sample Intake Valve 1 0 Close Sample Intake Valve 2 1 Open Sample Exhaust Valve 2 0 Close Sample Exhaust Valve 3 1 Begin Sample Sampling Stop Sample Sampling Turn On Control Pump 4 0 Turn Off Control Pump 5 1 Open Control Intake Valve 5 0 Close Control Intake Valve 6 1 Open Control Exhaust Valve 6 0 Close Control Exhaust Valve 7 1 Begin Control Sampling Stop Control Sampling Reinitialize SU s MAX Reinitialize MAX3107_HASP 8 2 Reinitialize MAX3107_SU 9 0 FF Changed Record Period 5 Table 2: SMITH Commands 1 Begin Sample Sampling command turns on the sample pump, opens the sample intake valve, and opens the sample exhaust valve, in that order. 2 Stop Sample Sampling command turns off the sample pump, closes the sample intake valve, and closes the sample exhaust valve, in that order. 3 Begin Control Sampling command turns on the control pump, opens the control intake valve, and opens the control exhaust valve, in that order. 4 Stop Control Sampling command turns off the control pump, closes the control intake valve, and closes the control exhaust valve, in that order. 5 Changed Record Period changes the period the data record is downlinked. The period can be changed from zero to 255 seconds depending on the second byte of the command. Zero in the second byte of the command changes the record period to zero seconds and FF changes the record period to 255 seconds. 22

23 Responses to commands are sent down to HASP in hexadecimal numbers from SMITH as part of the data record. The following are all the responses that can be received from SMITH by HASP: Table 3: Command from HASP to SMITH (byte one) Command from HASP to SMITH (byte two) Response to Command Meaning of Response Sample pump was turned on Sample pump was turned off Sample intake valve was opened Sample intake valve was closed Sample exhaust valve was opened Sample exhaust valve was closed Sample pump was turned on, Sample intake valve was opened, and Sample exhaust valve was opened Sample pump was turned off, Sample intake valve was closed, and Sample exhaust valve was closed Control pump was turned on Control pump was turned off Control intake valve was opened Control intake valve was closed Control exhaust valve was opened Control exhaust valve was closed Control pump was turned on, Control intake valve was opened, and Control exhaust valve was opened Control pump was turned off, Control intake valve was closed, and Control exhaust valve was closed MAX3107 was reinitialized on SUBR s Communications Board MAX3107_HASP was reinitialized on SMITH s Communications Board MAX3107_SU was reinitialized on SMITH s Communications Board 9 00 FF 80 Record period was changed Table 3: Command responses If $00 appears as the response to the command, this means that no command was executed because there was an invalid command or no command at all. 23

24 Other possible responses to commands incase an error incurred are also sent as hexadecimal numbers in the data record. They are: Table 4: Error Response to Error No Error 00 Wrong amount of bytes in RxFIFOLvl_HASP 91 First byte in RxFIFOLvl_HASP not equal to $01 92 Second byte in RxFIFOLvl_HASP not equal to $02 93 Fifth byte in RxFIFOLvl_HASP not equal to $03 94 Sixth byte in RxFIFOLvl_HASP not equal to $0D 95 Seventh byte in RxFIFOLvl_HASP not equal to $0A 96 Wrong amount of bytes in RxFIFOLvl_SU 97 Invalid command HIGHBYTE number 98 Invalid command LOWBYTE number 99 Table 4: Error Responses 4.2 Downlink Data The following table is a table of SMITH s data record. Table 5: Record Format Numbers Appearing Type Byte size on Ground Real Time Clock Date ASCII 3 Real Time Clock Hour ASCII 3 Real Time Clock Minute ASCII 3 Real Time Clock Second ASCII 3 Sample pump temp sensor ASCII 4 Sample motor temp sensor ASCII 4 Sample RPS counter ASCII 4 Control pump temp sensor ASCII 4 Control motor temp sensor ASCII 4 Control RPS counter ASCII 4 Sample State: ASCII 9 Pump MSB 0 or 1 Intake valve bit 6 0 or 1 Exhaust valve bit 5 0 or 1 Control State: Pump bit 4 0 or 1 Intake valve bit 3 0 or 1 Exhaust valve bit 2 0 or 1 Pressure ASCII 4 Temperature ASCII 4 Humidity ASCII 4 Last Command High 0 6 ASCII 3 24

25 Last Command Low 0 FF ASCII 3 Record Period ASCII 4 Command Response 51 58, 61 68, 70 ASCII 3 72, 75, 80, 85, 86 SMITH Error Response 00, 91 96, 98, 99 ASCII 3 SUBR Error Response 97 ASCII 3 Carriage Return 0D ASCII 2 Line Feed 0A ASCII 2 Table 5: SMITH s data record An example of SMITH s data record is as follows, 08,11,35,28,176,190,000,180,167,030, ,020,096,012,07,01,010,67,00,00, This record indicates that on the 8 th day at 11:35:28 CDT, the sample engine s ADC counts are 176 which correlate to a temperature of C and the sample motor s ADC counts are 190 which correlate to a temperature of C. The sample RPS indicates that the sample pump is not running because it reads 000 and therefore is not counting any RPS. The control engine s ADC counts are 180 which correlate to a temperature of C and the control motor s ADC counts are 167 which correlate to a temperature of C. The control RPS indicates that the control pump is running because it is counting 30 rotations per second. The state bits read that the sample pump is off and the sample intake and exhaust valves are closed and the control pump is on and the control intake and exhaust valves are open. The environmental pressure ADC counts are 20 which convert to mbars, the environmental temperature ADC counts are 96 which correlate to a temperature of C, and the environmental humidity ADC counts are 12 which converts to 4.24 percent relative humidity. The last command to be sent up was the command 07 01, which turns on the control pump and opens the control valves. The telemetry period is set to 10, ten seconds, and the command response reads 67 which mean the control pump has been turned on and the control valves have been opened. The SMITH error response reads 00, which means there were no errors dealing with the pump control software and the SUBR error response reads 00, which means there were no errors dealing with the environmental acquisition software. 5. Conclusion In conclusion, the software itself worked without a glitch. The pump control software and the environmental acquisition software did not have any problems running. Each of the subsystem s software flowed as expected. However, there were times when data was not received from the environmental acquisition microcontroller for pressure, temperature, or humidity. This is thought to be because of a timing issue between the two microcontrollers. This I would have done differently, time permitting. I would have tried to figure out the problem between the two microcontrollers and fix it. Also the hall effect sensors did not give valid readings, but this is thought to be because they were knocked off before flight. Other than these problems, everything else worked perfectly and I would not have changed a thing. 25