Project Goals:

Design a system that will:

• be used as an engineering tool to aid in future system development.
• have e-mail capability.
• allow expandability for future enhancements.
• utilize the capabilities of the Zilog Z80S183 mixed signal microprocessor.

The Data by Z-mail system is a bench top device that reads analog and digital data from a UUT (Unit Under Test) every hour and sends that data out via email and local RS-232. The Z-mail system is connected to desired test points of a UUT (e.g. machine, circuit board or test platform). The system then monitors and sends this data out via e-mail. This allows the engineer to monitor UUT data from any place in the world via email. Test points can be either analog or digital signals. The analog inputs can be from any device that outputs zero to five volts DC. The digital inputs can be from digital output type circuits. Example input devices that output analog voltages are: Pressure transducers, temperature sensors, photo sensors, power supplies and various outputs from analog circuitry. Example input devices that output digital signal levels are: Microprocessor outputs, intelligent sensors, PLC outputs and various outputs from digital circuitry.

System Applications

Given the remote data monitoring capability of the Data by Z-mail, how can it be used by the design engineer? The system can be used to monitor circuitry and components of a newly designed machine at a field test site and report that data back instantly via e-mail.

Once a newly designed machine has been tested in the lab, it then migrates to an actual customer/field test site. Unlike the lab environment, the test site is the true environment the machine will end up in. In an industrial environment, the machine may see new conditions like: high line voltage, line voltage with noise or spikes, excessive ambient temperatures, airborne contaminants, excessive humidity, static, etc. These types of conditions are the true test for the design. Unfortunately, these test sites are usually located far away from the design lab and retrieving engineering data from these machines can be difficult. The data retrieved is usually non-engineering in nature. Data like machine cycles and "The machine seems to be running good" are nice to hear, but what about the real data? What about temperatures of: the ambient environment, system components, heatsinks, transformers, transorbs, motors, solenoids, etc.? What about power supply levels and other analog voltages? The list could go on and on. These are important items for the design engineer.

As an example, if the line voltage is at the high end or over the specified level, this could provide excess stress on PCB power components like linear voltage regulators. If you could monitor the temperature of each heatsink or power device, you could easily see how this affects your design. Maybe a heatsink is not large enough or a component is under-powered. Without knowing this data, the machine may successfully pass all field tests and make it to final design. Many months after the machine has been release to production, there may be hundreds of machines in the field with failing voltage regulators due to excessive stress over time. These machines may now need retrofitting with a new board revision. This of course is costly and makes the design team look bad. If only you could have found this problem while at field test. This is where the Data by Z-mail system shines. It can send out this valuable engineering data via e-mail daily. The machine status can be reviewed and stored back at the design facility. The voltage regulator problem above could have been caught by the first e-mail sent out by the Z-mail system.

There are of course many other ways the Data by Z-mail system can be an effective piece of engineering equipment. Most applications will require custom Z183 software to take full advantage of the Z183 peripherals and capabilities. This will be discussed more in the "Future System Applications" section.

System Marketing

As described in the "System Applications" section, the Data by Z-mail system is an effective data monitoring system. But, what makes this any different or better than typical data monitoring/logging systems?

The major benefits of the Z-mail system over other data monitoring systems are: Low cost, email capability puts real-time data at engineers desktop, no local computer interface required for Z-mail data transfers, the ability for engineers to modify microprocessor source code for custom applications (Since the microprocessor is Zilog based and similar to the Z180, many engineers will know how to write code for this system.), mixed signal capabilities of Z183 processor provides versatility, future enhancement of entire system on a small form factor PCB allows for system to be mounted inside the UUT where applicable (See "Future System Revisions" section).

These features truly make this a valuable engineering tool.

Hardware Description

Microprocessor: The heart of the design is the Zilog Z80S183 8-bit mixed signal microprocessor. The Z183 peripherals are used to interface to external signals for data monitoring. The processor itself is a 100 pin VQFP package. The processor was placed on an adapter circuit board to go from surface mount to through hole. This allowed the processor to be wire wrapped on a prototype board.

Program Memory: Program memory is connected to the Z183 via a glueless connection thanks to the Z183 ROM signals. The device used is a Samsung K861000 128Kx8 SRAM connected to a Dallas battery backed DS1216 Smart socket. This combination is equivalent to a Dallas DS1245 device. An SRAM device was used to speed up the software development process. Rather than use an EPROM (UV) which requires timely erasures, this device can be reprogrammed instantaneously in a programmer. This device also resides in a latching socket. This allows quick removal and installation without damaging pins in the process. An EPROM socket was also placed on the board for a 27C64 device (8Kx8). This would allow the final program to reside in EPROM if desired.

RAM: The Z183 internal SRAM peripheral is used to store the constantly updating values of Port A and the A to D channels.

Reset: A power on reset circuit is connected to the Z183 reset pin. This circuit keeps the reset line low on turn on for a rate of T=RC or T=(2.2K Ohm*10 uF) * (5 for 100% charging of capacitor) = 110 mS. This gives an adequate reset signal on turn on. There is also a push button switch that shorts out this circuit to give a reset condition while power is on. This proves useful during development.

Digital I/O: The Z183 Port A is used as an 8-bit input port, monitoring digital signals.

Analog I/O: The Z183 Port D analog to digital converter peripheral is used to monitor 8 external analog voltage sources. The reference for this A to D is on the VCCA pin and is +5V. This gives a resolution of 5V/8-bits (255), which is 19.6 mV/bit. Each channel is protected from over-voltage inputs by a series resistor and diode connected to +5V. This limits the input voltage to around 5.6V. The analog output signal from the Z183 Digital to Analog converter peripheral is also brought out to the Data I/O connector. This output voltage can be used for future applications requiring a DAC output.

Serial Communications: The Z183 Port B asynchronous serial port peripherals (2) are used to communicate to the e-mail modem and a local PC. Both ports are interfaced to an LT1081 RS-232 transceiver for proper voltage level shifting. Each port is set to communicate at 9600 baud, N, 8, 1. LEDs were used to watch data flowing on these ports. At slower baud rates, this proved to be an effective troubleshooting tool.

For this application, both serial ports are used to transmit data only. The system wiring allows future applications to transmit and receive data.

Expansion Port: The Z183 Port C is divided in half. The lower 4 bits are used as future expansion I/O. The upper 4 bits are used to drive the on-board status LEDs located on the front panel. The status LEDs tell which state the system is in during data monitoring. Port C is also the Z183 programmable output generator peripheral. This function can be used on the lower 4 bits for future applications.

Power Supplies: The prototype board inputs 12 VDC from an external DC adapter module (wall wart). The 12 V goes through a series diode then to a 7805 5-V linear voltage regulator. The series diode protects the circuitry against an accidental reverse voltage condition (power supply input wires accidentally swapped). The 7805 regulator provides all the circuitry with 5 V for its power. There are two LEDs that are connected to the 5-V supply to show that power is on. One is on the board and the other on the front panel of the system.

Prototype board build: The prototype board material was a perforated type that was wire wrapped for a fast and low cost solution. Extra board space was left open for future design enhancements. A 5 V and ground strip were routed around the perimeter of the board for an easy access and reliable path for power. Local storage capacitors were place around this perimeter for signal integrity purposes.

E-mail Modem: The e-mail modem used, is the stand alone iModem from ConnectOne. Internally, the major components are the iChip from ConnectOne and a SocektModem from Conexant. The e-mail modem accepts AT+I serial RS-232 commands that pertain to creating and sending an e-mail. Some example commands are Subject ("SBJ") and To ("TO"). Once the iModem receives all the required commands, it dials the phone number for the Internet service provider, logs on to the account, sends the email and logs off. The iModem takes the burden of sending an e-mail off the local Z183 processor. The iModem helped reduce development time since the Z183 only had to send out serial data in order to have email capability.