LM3S811 Evaluation

Luminary Micro
        LM3S811 board

Luminary Micro’s LM3S811 board with on-board JTAG that can act as a probe for other Luminary Micro boards.

The LM3S811 was double the LM3S101’s price, but looking back at some earlier requests, it would have been a better warehouse display solution. There were two UARTs, a temperature sensor plus a lot more pins (48-pin package versus a 28-pin). The temperature sensor would be useful in hot countries for checking shelf temperatures of pharmaceuticals with a temperature profile across a complete warehouse to assist in cooling.

Sometime in either 2006 or 2007, we tested the Luminary Micro LM3S6965 which had Ethernet to see how it would compare for direct host connection and then controlling several RS-485 strings, but we never managed to do much with the code size limitation of the evaluation compiler, and hence the Ethernet would be discarded for the warehouse solution on low-cost micros. In the final days of the warehouse project, we proposed using the LM3S811 for the RS-232 to RS-485 control and to have a hierarchy of multi-drop strings. Each RS-485 buffer could communicate with 31 other similar buffers. More than this would have complicated the messaging or fault-finding. We did not test the communications between LM3S811 devices—instead we used its JTAG output to test the Ethernet board (also from Luminary). The small OLED display was on one of the serial interfaces (I2C interface), but other than a brief test, we would not be able to use them in industrial applications.

Luminary Micro did an excellent job in defining their I/O maps across the LM3Sxx family, which meant that code could run on other devices with little change. There were some details that prevented emulation of a LM3S101 with a LM3S811 device, but we will dig that out later. (One reason from the datasheets would be the LM3S101’s 20 MHz clock frequency versus the LM3S811’s 50 MHz.)

The tools that we wanted to test were CodeRed who claimed to handle profiling and tracing over the SWD interface. The evaluation documentation was dated September, 2006.

The SSI, I2C or second serial port (UART) could have connected displays on the same shelf without buffers, as the distance was under a foot. The RS-485 buffers cost almost as much as the LM3S101. Other options we considered were open-collector transistors along the same shelf (up to five display nodes). The RS-485 buffer turn-around problem with one pin short on the LM3S101 would also go away. By the time it came to the end of 2007, we had little time as my wife had a job offer in Australia and we would be leaving while the house was being renovated (just to add to the tight timelines!). Lets not mention the research that took a back seat as we tried to keep the finances in the black.