SPI Peripheral can only send a single byte #23
Description
Looking at the code in SpiPeripheral : https://github.com/OSVVM/SPI_GuyEschemann/blob/77d1e30c494d0e6032918cde70c179a5b575976a/src/SpiPeripheral.vhd#L267
It appears this code can only send a single byte without raising and re-asserting CSEL. It is pretty common in a SPI interface to send multiple bytes per transaction for as long as the controller holds CSEL low.
Currently, the while loop is exited while, but it then has a
wait until CSEL = '0'
which requires an event on CSEL to re-enter and send more data. This line should probably be:
if CSEL = '1' then wait until CSEL = '0' end if;
but with this, you will need to somehow catch when CSEL rises to 1 if the transaction is actually ended at the end of the current byte.
You could probably do this with the following code:
if CSEL = '1' then
wait until CSEL = '0';
bitIdx := TxData'high;
end if;
if OptSpiMode = 0 or OptSpiMode = 3 then
wait until falling_edge(SCLK) or CSEL = '1';
else
wait until rising_edge(SCLK) or CSEL = '1';
end if;
if CSEL = '1' then
next;
end if;
if bitindex = TxData'high then
if not Empty(TransmitFifo) then
TxData := Pop(TransmitFifo);
else
TxData := (others => 'X'); -- X would be better here IMO to differentiate from actual data transmission
end if;
end if;
while CSEL = '0' and BitIdx >= 0 loop
POCI <= TxData(BitIdx) when OptSpiMode = 0 or OptSpiMode = 2;
if OptSpiMode = 0 or OptSpiMode = 3 then
wait until falling_edge(SCLK);
else
wait until rising_edge(SCLK);
end if;
POCI <= TxData(BitIdx) when OptSpiMode = 1 or OptSpiMode = 3;
BitIdx := BitIdx - 1;
end loop;
bitIdx := TxData'high when bitIdx < 0;