In order to use the safeload write feature on the ADAU1701 (also ADAU1702, ADAU1401, and ADAU1401A), a very specific sequence of write commands must be executed. The write sequence is as follows:
Up to 5 target addresses may be written. The writes marked "optional" in the list above only need to be included if more than one parameter is being updated.
The format for the Safeload Address and Safeload Data registers is as follows (from the ADAU1701 datasheet):
A simple example of using the Safeload Data 0, Safeload Address 0, and IST (initiate safeload transfer bit) to set a volume control to 0 dB in parameter memory is shown below. In this example, the target address in parameter RAM is 0x0000. Since only one parameter is being updated, the Data 1, Data 2, Data 3, Data 4, Address 1, Address 2, Address 3, and Address 4 registers may be ignored.
//Write 0x00800000 to set volume to 0 dB08 10 00 00 80 00 00 //Data 008 15 00 00 //Address 008 1C 00 3C //Set IST High
//Write 0x00800000 to set volume to 0 dB
08 10 00 00 80 00 00 //Data 008 15 00 00 //Address 008 1C 00 3C //Set IST High
In the case where multiple parameters need to be updated, the additional parameter data and address registers may be used. The following example shows the 5 parameters of an IIR filter being updated.
//Write 1kHz, +5 dB peaking filter coefficients08 10 00 00 83 57 7E //Data 008 15 00 00 //Address 008 11 00 FF 0A B4 47 //Data 108 16 00 01 //Address 108 12 00 00 74 12 18 //Data 208 17 00 02 //Address 208 13 00 00 F5 4B B9 //Data 308 18 00 03 //Address 308 14 00 FF 88 96 6B //Data 408 19 00 04 //Address 408 1C 00 3C //Set IST High
//Write 1kHz, +5 dB peaking filter coefficients
08 10 00 00 83 57 7E //Data 008 15 00 00 //Address 008 11 00 FF 0A B4 47 //Data 108 16 00 01 //Address 108 12 00 00 74 12 18 //Data 208 17 00 02 //Address 208 13 00 00 F5 4B B9 //Data 308 18 00 03 //Address 308 14 00 FF 88 96 6B //Data 408 19 00 04 //Address 408 1C 00 3C //Set IST High
Only one safeload write operation should be attempted per each audio frame.
I wonder if it's possible to write to safeload address registers and safeload data registers in a burst mode (address of the first safeload address/data register and then up to 5 parameter addresses or datasets).
It would save significant amount of bytes written in my case.
Hi genp,
You can always write these values directly to parameter RAM, bypassing the need for safeload entirely. The only problem is that if you are unlucky and end up writing to a parameter at the exact moment it's being updated by the control port, there might be an audible artifact on the output. That's the problem Safeload was originally designed to solve.
However, for the sake of speed, you could possibly write to memory directly, if you're OK with the tradeoff of possibly having audible artifacts.
It might be worth testing just to see how bad it is. Maybe it's not even noticeable!
Hi Yagami,
unfortunately, you are absolutely right.
In a current project for sound development I need to update 6 input levels on 4 mixers every 10 mS.
It's 24 levels with 3 writes for each updates = 72 writes.
In the previous project (on 1442) I had 22 12-input mixers, but was able to use DMA due to
sequential writes.
Hi Gennady,
I may be wrong, but I think you're only able to do the trick where you keep the chip select line low throughout the duration of the writes when you are writing to contiguous (sequential) addresses in memory. Since your target addresses 0x0810, 0x0815, and 0x081C are not sequential, I imagine that you need to bring the chip select line high between each of the three writes.
Another clarification required, please.
Some details are skipped in this otherwise great description.
I am using SPI port for communication.
According to the datasheet, every message requires first byte 0x00 (in my case) of device address and Write.
So do I need to latch every message like this (the above single write is used as an example):
CS LOW
00 08 10 00 00 80 00 00 //Data 0
CS HIGH
CS LOW00 08 15 00 00 //Address 0
CS LOW00 08 1C 00 3C //Set IST High
or do I latch the whole packet:
00 08 15 00 00 //Address 0
00 08 1C 00 3C //Set IST High
I remember that when using 1442 I used DMA for safeload write, so I did latch the whole packet.
On 1701 it doesn't seem to work, or I am doing something wrong.
Thank you,
Gennady