Posted on March 11, 2017 at 17:18Ok, So after digging a little more, i now know why i can't do what i was trying to do. Each DMA at a specific time step is only going to stransfer one piece of info from one point to another. My original intent was to have 3 ADCs simultaneously measuring values, drawing said values to separate buffers over DMA. On the STM32F407VG i'm using dedicates DMA2 to all ADCs, therefore i cannot physically write ADC values at the same exact time step to separate buffers since they all have to go across DMA2. So if i wanted to do 3 independant ADCs over DMA, they will be spaced apart by some sort of lag regardless since they all have to use the same DMA. Next i thought, well i could use Triple mode and at least have them organized and minimal time difference between each sample. With that i wanted to then use MEMTOMEM to separate the values from the one buffer that triple mode writes to into separate buffers, BUT MEMTOMEM also requires using DMA2, thus i cannot do that. Therefore i can only draw values over triple mode, then postprocess the data to separate the ADC outputs. Or use DMA MEMTOMEM after i'm done reading ADCs. If you use an MCU that has MEMTOMEM on separate DMAs OR the ADCs are on separate DMAs, then you can pull this off.
Finally, to my original question. the most basic settings to get an ADC to sync with a timer, you can select a timer with a 'trigger out' event in the ADC settings: (C
onfiguration | ADC | ADC_Regular_Conversion_Mode | External Trigger Conversion Source)
Then under the timer settings: (C
onfiguration | TIM# | Trigger Event Selection) You can select 'Update Event'. Not all timers have a 'Trigger Out' event, and i think the method above using Capture Compare Events works as well, as long as you select the correct trigger event selection in the timer settings (i don't know which setting is needed for a capture compare event yet) And the Timer settings under 'Pinout' are set to 'Output Compare, No Output' on a channel and then the channel is the 2nd Number on the '
External Trigger Conversion Source' Capture Compare Event in the ADC settings.
So my solution to 3 ADCs simultaneously is to use the triple mode (Make sure you use 'HAL_ADC_Start' for ADC2 and ADC3 1st, then '
HAL_ADCEx_MultiModeStart_DMA
' for ADC1) to write data to a single buffer, use the MCU to write the values to a separate FLASH buffer, and either have buffer large enough to encompass all the data i want to capture, or have the write to flash rate be as minimal as i can to effectively capture the data i need.
Please anyone feel free to correct anything i wrote on the wall of text above, thanks!
