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_timed(): now allows indirect control of intern prescaler via max expected cycles count

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This commit is contained in:
Philippe Teuwen 2011-05-12 20:33:00 +00:00
parent b9bcfaf959
commit e5601e562f
2 changed files with 20 additions and 4 deletions
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12
libnfc/chips/pn53x.c
View file

@ -1109,7 +1109,7 @@ pn53x_initiator_transceive_bytes (nfc_device_t * pnd, const byte_t * pbtTx, cons
return true; return true;
} }
void __pn53x_init_timer(nfc_device_t * pnd) void __pn53x_init_timer(nfc_device_t * pnd, const uint32_t max_cycles)
{ {
// The prescaler will dictate what will be the precision and // The prescaler will dictate what will be the precision and
// the largest delay to measure before saturation. Some examples: // the largest delay to measure before saturation. Some examples:
@ -1117,7 +1117,11 @@ void __pn53x_init_timer(nfc_device_t * pnd)
// prescaler = 1 => precision: ~221ns timer saturates at ~15ms // prescaler = 1 => precision: ~221ns timer saturates at ~15ms
// prescaler = 2 => precision: ~369ns timer saturates at ~25ms // prescaler = 2 => precision: ~369ns timer saturates at ~25ms
// prescaler = 10 => precision: ~1.5us timer saturates at ~100ms // prescaler = 10 => precision: ~1.5us timer saturates at ~100ms
CHIP_DATA (pnd)->timer_prescaler = 0; if (max_cycles > 0xFFFF) {
CHIP_DATA (pnd)->timer_prescaler = ((max_cycles/0xFFFF)-1)/2;
} else {
CHIP_DATA (pnd)->timer_prescaler = 0;
}
uint16_t reloadval = 0xFFFF; uint16_t reloadval = 0xFFFF;
// Initialize timer // Initialize timer
pn53x_write_register (pnd, PN53X_REG_CIU_TMode, 0xFF, SYMBOL_TAUTO | ((CHIP_DATA (pnd)->timer_prescaler >> 8) & SYMBOL_TPRESCALERHI)); pn53x_write_register (pnd, PN53X_REG_CIU_TMode, 0xFF, SYMBOL_TAUTO | ((CHIP_DATA (pnd)->timer_prescaler >> 8) & SYMBOL_TPRESCALERHI));
@ -1213,7 +1217,7 @@ pn53x_initiator_transceive_bits_timed (nfc_device_t * pnd, const byte_t * pbtTx,
return false; return false;
} }
__pn53x_init_timer(pnd); __pn53x_init_timer(pnd, *cycles);
// Once timer is started, we cannot use Tama commands anymore. // Once timer is started, we cannot use Tama commands anymore.
// E.g. on SCL3711 timer settings are reset by 0x42 InCommunicateThru command to: // E.g. on SCL3711 timer settings are reset by 0x42 InCommunicateThru command to:
@ -1308,7 +1312,7 @@ pn53x_initiator_transceive_bytes_timed (nfc_device_t * pnd, const byte_t * pbtTx
return false; return false;
} }
__pn53x_init_timer(pnd); __pn53x_init_timer(pnd, *cycles);
// Once timer is started, we cannot use Tama commands anymore. // Once timer is started, we cannot use Tama commands anymore.
// E.g. on SCL3711 timer settings are reset by 0x42 InCommunicateThru command to: // E.g. on SCL3711 timer settings are reset by 0x42 InCommunicateThru command to:

12
libnfc/nfc.c
View file

@ -560,6 +560,12 @@ nfc_initiator_transceive_bits (nfc_device_t * pnd, const byte_t * pbtTx, const s
* - It only supports mode with \a NDO_EASY_FRAMING option disabled. * - It only supports mode with \a NDO_EASY_FRAMING option disabled.
* - Overall communication with the host is heavier and slower. * - Overall communication with the host is heavier and slower.
* *
* Timer control:
* By default timer can count up to 65535 cycles, so about 4.8ms, with a precision of about 73ns.
* - If you're ok with the defaults, set *cycles = 0 before calling this function.
* - If you need to count more cycles, set *cycles to the maximum you expect but don't forget
* you'll loose in precision and it'll take more time before timeout, so don't abuse!
*
* @warning The configuration option \a NDO_EASY_FRAMING must be set to \c false. * @warning The configuration option \a NDO_EASY_FRAMING must be set to \c false.
* @warning The configuration option \a NDO_HANDLE_PARITY must be set to \c true (the default value). * @warning The configuration option \a NDO_HANDLE_PARITY must be set to \c true (the default value).
*/ */
@ -579,6 +585,12 @@ nfc_initiator_transceive_bytes_timed (nfc_device_t * pnd, const byte_t * pbtTx,
* - It only supports mode with \a NDO_EASY_FRAMING option disabled and CRC must be handled manually. * - It only supports mode with \a NDO_EASY_FRAMING option disabled and CRC must be handled manually.
* - Overall communication with the host is heavier and slower. * - Overall communication with the host is heavier and slower.
* *
* Timer control:
* By default timer can count up to 65535 cycles, so about 4.8ms, with a precision of about 73ns.
* - If you're ok with the defaults, set *cycles = 0 before calling this function.
* - If you need to count more cycles, set *cycles to the maximum you expect but don't forget
* you'll loose in precision and it'll take more time before timeout, so don't abuse!
*
* @warning The configuration option \a NDO_EASY_FRAMING must be set to \c false. * @warning The configuration option \a NDO_EASY_FRAMING must be set to \c false.
* @warning The configuration option \a NDO_HANDLE_CRC must be set to \c false. * @warning The configuration option \a NDO_HANDLE_CRC must be set to \c false.
* @warning The configuration option \a NDO_HANDLE_PARITY must be set to \c true (the default value). * @warning The configuration option \a NDO_HANDLE_PARITY must be set to \c true (the default value).