I am using TMS320F28235 to do ADC tests.
The problem is that the ADC conversion time is different between seq1 and seq2.
And ACQ_PS does not take effect for seq2.
Please see the test record below.
Mode | Channel | Conv. Count | ACQ_PS | T(us) |
Sequence | 1 | 8 | 0 | 2.3 |
Sequence | 1 | 8 | 9 | 5.1 |
Sequence | 8 | 8 | 0 | 0.9 |
Sequence | 8 | 8 | 9 | 0.9 |
Cascaded | 1 | 8 | 0 | 2.4 |
Cascaded | 1 | 8 | 9 | 5.2 |
Cascaded | 8 | 8 | 0 | 2.4 |
Cascaded | 8 | 8 | 9 | 5.2 |
The time was measured from setting SOC_SEQx to SEQx_BSY cleared.
Other ADC registers were set default values.
CLKIN=HSPCLK=ADCCLK=25MHz.
I think the time for a 8-sampling seq conv is calculated like,
2 + 8 * (1+1) + 2 ADCCLK = 20 * 40ns = 0.8us. (ACQ_PS=0)
2+ 8 * (10+1) + 2 = 85 * 40ns = 3.4us (ACQ_PS=9).
The code was posted in another thread,
http://e2e.ti.com/support/microcontrollers/c2000/f/171/p/272341/952264.aspx#952264