SPI write problems on an own reflown FXOS8700 I have reflowed an FXOS8700 to my own development card as an breakout to be able to use it in a project. I am now unsure if it works proper or not. Is the possibility to read but not write a sign of a burnt FXOS8700 in the reflow process???? SPI setting are CPOL=0 and CPHA=0: I have no problem to read from an address, but problem to read back what was written. This is my sequence of SPI commands: // WHO AM I SPI_ReadFXOS(WHO_AM_I, rbuf, 1); sprintf_P(buffer_0, PSTR("\r\n::WHO AM I = 0x%X\r\n\r\n"), rbuf[0]); uart_puts(buffer_0); => 0xC7 // Temperature SPI_ReadFXOS(TEMP, rbuf, 1); sprintf_P(buffer_0, PSTR("\r\n::TEMP = %i\r\n\r\n"), rbuf[0]); uart_puts(buffer_0); => 21 Both above works as aspected!!!! // Acc + Mag TEST SPI_WriteFXOS(CTRL_REG1, 0x00); // Set to standby mode SPI_ReadFXOS(CTRL_REG1, rbuf, 1); sprintf_P(buffer_0, PSTR("\r\n::CTRL_REG1 = 0x%X\r\n\r\n"), rbuf[0]); uart_puts(buffer_0); SPI_WriteFXOS(M_CTRL_REG1, 0x1F); // 200 Hz hybrid mode SPI_ReadFXOS(M_CTRL_REG1, rbuf, 1); sprintf_P(buffer_0, PSTR("\r\n::M_CTRL_REG1 = 0x%X\r\n\r\n"), rbuf[0]); uart_puts(buffer_0); => 0x00 Writing to M_CTRL_REG1 does not work but gives 0x00 back ...... Accelerometers Magnetic Sensors Re: SPI write problems on an own reflown FXOS8700 Thanks a bizillion times Tomas! You are my hero and made my day, truly I had used a macro (atmega8) in as if it returned the first bit as set, and it stayed to the second byte ... Now all three modules work just fine!!!! Best Regards, Hans-Henrik P.S: For anyone interested in atmega8 code looks like: // Set FXOS8700 in SPI mode void init_spi(void) { FXOS_SS_ENABLE; // To open tri-state buffer and set MISO high MISO_HI; // SPI init demands SA0/MOSI high during reset FXOS_RESET_HI; // Active high _delay_ms(1); // ?? FXOS_RESET_LO; _delay_ms(1); // FXOS8700 Datasheet defines 1ms wait after reset [p.19] FXOS_SS_DISABLE; } // Read values from register FXOS8700 void SPI_ReadFXOS(uint8_t reg, volatile uint8_t* rbuf, uint8_t len) { FXOS_SS_ENABLE; ATOMIC_BLOCK(ATOMIC_RESTORESTATE) { SPDR = cbi(reg,7); // Transmit; clear bit 7 for reading + 7 bits of register address while(!(SPSR & 1< SPDR = reg; // Transmit bit 7 of register address while(!(SPSR & 1< for(uint8_t i=0; i SPDR = 0x00; // Transmit while(!(SPSR & 1< rbuf[i] = SPDR; // Clear SPIF flag 2/2 } } FXOS_SS_DISABLE; // 2) For ISR context switcher which re-enable SPI unit } // Write value to register FXOS8700 <------------------------- ineffektiv loop void SPI_WriteFXOS(uint8_t reg, uint8_t val) { FXOS_SS_ENABLE; uint8_t reg1 = reg; sbi(reg1,7); uint8_t wbuf[3] = {reg1, reg, val}; // Two bytes for write bit and address ATOMIC_BLOCK(ATOMIC_RESTORESTATE) { for(uint8_t i=0; i<3; i++) { SPDR = wbuf[i]; // Transmit while(!(SPSR & 1< } } FXOS_SS_DISABLE; // 2) For ISR context switcher which re-enable SPI unit } Re: SPI write problems on an own reflown FXOS8700 Just for illustration, here is an example of writing/reading the value of 0x3D to/from the CTRL_REG1 (0x2A): Best regards, Tomas Re: SPI write problems on an own reflown FXOS8700 Hi Hans-Henrik, It seems like your both write sequences are not correct. The order of the bits is as follows: Byte 0: R/W, ADDR[6], ADDR[5], ADDR[4], ADDR[3], ADDR[2], ADDR[1], ADDR[0] Byte 1: ADDR[7], X, X, X, X, X, X, X Byte 2: DATA[7], DATA[6], DATA[5], DATA[4], DATA[3], DATA[2], DATA[1], DATA[0] The first byte you are sending is correct, but the MSB bit of the second byte (ADDR[7]) should be "0" and not "1". So instead of sending 0xDB, 0xDB, 0x1F, try to send 0xDB, 0x00, 0x1F. Then send 0x5B, 0x00, 0x00 to read back 0x1F from the M_CTRL_REG1 register. Hope it helps. Best regards, Tomas Re: SPI write problems on an own reflown FXOS8700 Now I have reflowed another two FXOS8700 vary carefully, and both of them show identical characteristics. It is not possible to write to a register and than read it back, what can possible be wrong??
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