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juanodiy
Joined: 07 Sep 2012
Posts: 17
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 Posted: Tue Sep 11, 2012 12:44 am |
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| Quote: |
Using SPI, you could use a single other line as a 'A/B' identifier, and change this according to which channel you are sending, allowing the slave device to always 'know' which channel it is receiving.
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This is very interesting, I'm doing this but with a counter in the slave, every arrives byte is counted, but is not very efficient I think, if you can help with this part, I will be very happy , thanks very much for the observation |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19536
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| Posted: Tue Sep 11, 2012 2:55 am |
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The problem is not 'efficiency', but if the slave wakes out of sync with the master, or a transaction is missed, the channels will be swapped....
Only an 'overview', but hopefully will give you some ideas:
| Code: |
//in both master and slave
#define SPI_MODE_0 (SPI_L_TO_H | SPI_XMIT_L_TO_H)
#define SPI_MODE_1 (SPI_L_TO_H)
#define SPI_MODE_2 (SPI_H_TO_L)
#define SPI_MODE_3 (SPI_H_TO_L | SPI_XMIT_L_TO_H)
//master
#define ABselect PIN_xx //set to suit your hardware
#define CSoutput PIN_yy //again set to suit your hardware connects to SS
//input on slave
int1 channel=0;
int8 val;
setup_spi(SPI_MASTER,|SPI_CLK_DIV_4|SPI_MODE_0);
//obviously need your ADC configuration etc. here
set_adc_channel(channel)
output_high(CSoutput);
delay_us(13);
do {
read_adc(ADC_START_ONLY); //start the ADC reading
set_adc_channel(channel^1); //swap ADC channels
output_bit(ABselect,channel); //output bit to say which channel
//Now wait for the ADC to complete
while (!adc_done()) ;
//ADC starts acquiring the new channel _immediately_ here
val=read_adc(ADC_READ_ONLY); //read the value
output_low(CSoutput);
spi_write(val);
output_high(CSoutput);
channel^=1; //toggle channel
delay_us(5); //ensure acquisition has completed
} while(TRUE);
//slave
#define ABinput pin_zz //again set to suit your input, connected to ABselect
int1 channel=0;
int8 val[2];
setup_spi(SPI_SLAVE,|SPI_MODE_0);
do {
//wait for byte from master
while (!SPI_DATA_IS_IN) ;
channel=input(ABinput);
val[channel]=spi_read();
//then process the data
} while(TRUE);
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Not complete, and probably with some errors, but hopefully will give you some ideas. Note the 'overlapping' of jobs. While the ADC is acquiring, I get on doing some other things, including selecting the next channel, which means the ADC will begin Tacq, as soon as the reading is complete.
Best Wishes |
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juanodiy
Joined: 07 Sep 2012
Posts: 17
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| Greats |
| Posted: Wed Sep 19, 2012 10:08 pm |
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Thanks to all, in special to Ttelmah, I can do it finally , I learn so much with this, and Ttelmah you are a genius man, really you are a master, thank you very much for your help, and thanks to the forum.
| Quote: |
Not complete, and probably with some errors, but hopefully will give you some ideas. |
many ideas, your awesome man, thank you. |
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