问: I want to use the ADS1298ECGFE EVM without the MMB0, is this possible?
答: Yes! Absolutely! There are a few things you need to consider first:
- Board Power
The power for the ADS1298ECGFE board is delivered through J4; a 10-pin 2 row female socket. By way of the MMB0 connector J5; +5V, +3.3V and +1.8V is delivered to the ADS1298 board. The +5V supply goes through regulators which provide the analog voltage to the ADS1298 chip. The analog rails are either 0V and +3.3 or +/-2.5V depending on JP2 and JP24. The digital rail of the ADS1298 is configured via JP28. You can choose to use the 3.3V source (short JP28 pins 2-3) or the 1.8V source (short JP28 pins 1-2). The actual applied voltage does not need to be connected to J4 directly, it can be applied to test points TP7 (the +5V), TP9 (+1.8V) and TP10 (+3.3V). Ground is available through TP1, TP8, TP11; J4 pins 5 and 6; and J3 pins 4, 10 and 18.
- SPI Interface
The SPI communication requires a minimum 3-wire interface with SCLK, SOMI and SIMO. The ADS1298 is a SLAVE device and is not capable of generating a serial clock. The SCLK line is on J3 pin 4. SIMO and SOMI are located on J3 pins 11 and 13 respectively. The SCLK should dwell low, with valid data on the falling clock edge. This is most often considered to be SPI mode 1.
问: Where are the Gerber files for the ADS1298ECGFE-PDK Boards?
答: Here are the Gerber files for the ADS1298ECGFE-PDK, the ADS1298RECGFE-PDK and the ADS1198/1298ECGFE-PDK in TQFP packages.
- ADS1298ECGFE-PDK Rev A - BGA Version
- ADS1198/1298ECGFE-PDK Rev C - TQFP Version
- ADS1298RECGFE-PDK Rev B - BGA Only
问: What do I do with the DRDY output? My processor does not have a DRDY input so I'm not sure where to connect this signal.
答: The DRDY output of the ADS1298 is intended to act as an interrupt to your host processor. Most micro controllers or digital signal processors have the ability to be 'interrupted' while performing comuptations by an external peripheral - like the ADS1298 connected to an SPI port. The code developer would then put something into an interrupt service routine (ISR) that, when ready, the controller would perform the task associated with the ISR. For the ADS1298, that might be to go read eight channels worth of data along with the status byte - 9*24-bits of information to store and process.
问: What is the purpose of the MSP430G2121` on the ADS1298RECGFE-PDK?
答: The MSP430G2121 on the ADS1298RECGFE-PDK board is there to help simulate respirations. It is factory programmed (through J7) to create a square wave of 0.1 to 0.5Hz. The frequency is selectable in the GUI as 0.1, 0.2, 0.3 (default), 0.4 or 0.5Hz. That signal is fed through JP36 to a comparator (U12 pin 2) and the output of the comparator drive the analog switch (U11). If you want to use your own signal generator to simulate respiration, you can apply a square wave to the SMA connector (J6) and move the shunt on JP36 to cover pins 2-3.
The MSP430 is there only to help you evaluate the respiration function without having to connect additional test gear to the EVM. You do not need to put anything from your processor into J7. J7 is there to accommodate the Spy-Bi-Wire Interface of the MSP430G2121 only, which is how we programmed the device to generate the square wave mentioned above.
问: What is the purpose of the EEPROM on the ADS1298 and what data does it contain?
答: The EEPROM located at U16, just south of J3 on the ADS1298ECGFE board contains data pertinent to the assembly level of the board. It contains a unique part number for the assembly as well as the assembly revision of the board. There is nothing in the EEPROM that the end user need to be concerned with - the ADS1298ECGFE-PDK software does not interrogate the EEPROM and it contains no 'boot data' needed to run the GUI.
问: What do I do with the DRDY output? My processor does not have a DRDY input so I'm not sure where to connect this signal.
答: The DRDY output of the ADS1298 is intended to act as an interrupt to your host processor. Most micro controllers or digital signal processors have the ability to be 'interrupted' while performing comuptations by an external peripheral - like the ADS1298 connected to an SPI port. The code developer would then put something into an interrupt service routine (ISR) that, when ready, the controller would perform the task associated with the ISR. For the ADS1298, that might be to go read eight channels worth of data along with the status byte - 9*24-bits of information to store and process.
问: What is the maximum SCLK speed that I can apply to the ADS1298?
答:The maximum SCLK speed depends on the applied DVdd voltage. For DVdd between 2.7 and 3.6VDC, the fastest SCLK you can is is 20MHz (50ns period). Below 2.7V, the SCLK is limited to a period of 66.6ns or approximately 15MHz.
问: What's the difference between ADS1298/ADS1298R?
答: The main difference between the ADS1298 and ADS1298R is that the ADS1298R has integrated respiration impedance measurement functionality associated with CH1 (see the note at the top of page 9 in the data sheet). Other than that, they are the same. For more details on how the function works, please feel free to review this application note:
Respiration Rate Measurement Using Impedance Pneumography
The ADS1298R will not be offered in the TQFP package, it will only be available in the BGA version.
问. I just received my ADS1298ECGFE-PDK and get a constant error message "Download failed..reset the hardware". What can be wrong?
答. The message is caused when the PC does not see the MMB0. It should also be followed up by a dialog box that pops up with a message "The firmware load has failed due to a timeout condition. Please reset the hardware to continue loading the firmware." Let's first address the potential hardware issues:
To debug the MMB0 hardware, there are a couple of things to look for, first is a shunt jumper on J12 which is a two pin jumper just below and slightly left of the power jack on the MMB0. If this shunt came off through the shipping process for some reason, you would get the error message you describe. The second possibility is that the MMB0 is not configured for USB Boot Mode. If you have the REV C version of the MMB0 (REV C has four standoffs mounted on the bottom of the board, REV D has four rubber 'stick-on' feet) there is a switch just to the right of the power jack. This switch needs to be in the USB position (towards the center of the board) for the firmware to properly load. The REV D version of the board does not have this switch installed, the USB boot mode is set by virtue of a wired short on S4. The final possibility is the actual RESET switch. The RESET switch (S3) is in the upper right corner of the MMB0 - while rare, we have had a few of these switches fail short on the REV C boards. If you do not 'feel' the switch give under the pressure of a press with your finger, verify the switch reads 'open' or infinite resistance using a multi-meter between the two outside pins in the upper right corner of the board.
If J12, S4 and S3 are configured properly, the next item to look for is that the drivers for the MMB0 are actually getting loaded on your PC. After installing the software and powering up the board for the first time, with the USB cable plugged in, you should get the 'Found New Hardware' prompt. The first driver that gets installed is the NI-VISA USB Device Driver. Select the 'No, not this time' and 'Install the software automatically' options when prompted. After installing the device driver, the device manager should show a NI-VISA USB Devices type with TMS320VC5509A (NI-VISA) driver. From here, once you start the ADS1298 software for the first time, you should get another prompt regarding the finding of a new device. The second driver is the USBStyx Driver, again follow the prompts as above (don't search, automatically install) and let the installation finish. During this period, the firmware may timeout and give you the "Download failed..reset the hardware", but pressing the reset button at this point or re-starting the ADS1298ECG-FE GUI should clear that message.
ADS1298 的文档资料: http://e2e.ti.com/support/data_converters/precision_data_converters/m/videos__files/default.aspx
