TI E2E Community
Precision Data Converters
Precision Data Converters Forum
F28335 with ADS8556
I am using F28335 and need to interface upto 24 external ADC channels from ADS8556 with the MCU ( these are additional channels beyond the inbuilt ADC). What is the best way to interface - SPI / McBSP?
Also, will I need to use an external channel multiplexer if using McBSP ?
A possibility might be to use the parallel interface mode. The TMS320F28335 supports an external memory interface called the XINTF. You need to have some logic to expand the addresses with the 3 chip selects available on the interface.
Actually I plan to have following interfaces on F28335 -
1. 16 channels using in-built ADCs
2. 24 external ADC channels
3. MCU - FPGA via EMIF/XINT
4. External SDRAM via EMIF/XINT
Given these interfaces, I think I will have to share the XINT address space for external RAM and FPGA connections; can ADC channels still be shared on same XINT ?
In this scenario, will McBSP be a better option ... want your suggestions on these interfaces
I don't see any reason why keeping the ADS8556 on the EMIF would be an issue. You'd have to address decode the /CS input (using something like an SN74HC138) and you could potentially use the SOC from the F28335 to trigger the CONVST inputs. I believe the McBSP is in the low-speed clock domain which might be problematic in your control loop if you used the serial mode of the ADS8556.
Thank you for your reply. I tried looking up some documentation and example code like adc_on_xintf and xintf_run_from. I'm not sure if I can use ADC channels, FPGA connection and SARAM simultaneously using same XINTF. Given a single data bus XD [31:0], even if I allocate something like ADC on Zone 0, FPGA on Zone 6 and may be SARAM on Zone 7 (separately addressed), can all interfaces work in parallel ?
How is your project going?
I'm working on the memory interface part of the project (FPGA-DSP via XINT, working on eZdsp). The issue of ADC channels has been solved. However, I'm looking into the analog pre-processing of the ADC inputs, especially for the inbuilt channels on F28335, by using something like INA 159. Can you suggest any reference designs for the same ?
I am glad to hear you are making progress! I've not worked much with the ADC's inside the F28335. You might try cruising around in the C2000 forum to see if there are any references there.
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with respect to these materials. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.